Change search
Refine search result
12 1 - 50 of 83
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Ah-King, Malin
    et al.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Sex in an Evolutionary Perspective: Just Another Reaction Norm2010In: Evolutionary biology, ISSN 0071-3260, E-ISSN 1934-2845, Vol. 37, no 4, p. 234-246Article, review/survey (Refereed)
    Abstract [en]

    It is common to refer to all sorts of clear-cut differences between the sexes as something that is biologically almost inevitable. Although this does not reflect the status of evolutionary theory on sex determination and sexual dimorphism, it is probably a common view among evolutionary biologists as well, because of the impact of sexual selection theory. To get away from thinking about biological sex and traits associated with a particular sex as something static, it should be recognized that in an evolutionary perspective sex can be viewed as a reaction norm, with sex attributes being phenotypically plastic. Sex determination itself is fundamentally plastic, even when it is termed "genetic". The phenotypic expression of traits that are statistically associated with a particular sex always has a plastic component. This plasticity allows for much more variation in the expression of traits according to sex and more overlap between the sexes than is typically acknowledged. Here we review the variation and frequency of evolutionary changes in sex, sex determination and sex roles and conclude that sex in an evolutionary time-frame is extremely variable. We draw on recent findings in sex determination mechanisms, empirical findings of morphology and behaviour as well as genetic and developmental models to explore the concept of sex as a reaction norm. From this point of view, sexual differences are not expected to generally fall into neat, discrete, pre-determined classes. It is important to acknowledge this variability in order to increase objectivity in evolutionary research.

  • 2. Anrup, Roland
    et al.
    Fareld, Victoria
    Stockholm University, Faculty of Humanities, Department of Literature and History of Ideas, History of Ideas.
    Fornäs, Johan
    Frisk, Syliva
    Fur, Gunlög
    Ganetz, Hillevi
    Stockholm University, Faculty of Humanities, Department of Ethnology, History of Religions and Gender Studies, Gender Studies.
    Gardell, Mattias
    Hedman Hvitfeldt, Maria
    Höghede, Erika
    Iordanoglou, Dimitrios
    Jalmert, Lars
    Stockholm University, Faculty of Social Sciences, Department of Education.
    Johansen, Maria
    Jonsson, Stefan
    Josephson, Peter
    Karlsohn, Thomas
    Laikre, Linda
    Stockholm University, Faculty of Science, Department of Zoology.
    Larsson, Åsa Bharathi
    Lorenzoni, Patricia
    Liedman, Sven-Eric
    Madison, Guy
    Manga, Edda
    Munthe, Christian
    Nilsson, Ulrika
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Olsson, Erik J.
    Peralta, Julia
    Persson, Mats
    Priebe, Gunilla
    Rider, Sharon
    Rooke, Tetz
    Rådström, Niklas
    Söderblom, Staffan
    Sörensen, Jens
    Tydén, Mattias
    Stockholm University, Faculty of Humanities, Department of History.
    Zetterholm, Magnus
    Öberg, Johan
    Centrala universitetsvärden hotas av bolagiseringsidén2013In: Dagens nyheter, ISSN 1101-2447Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    Högskolestiftelser. Förslaget att driva svenska universitet i stiftelseform ­öppnar för bolagisering. Men det är ingen riktig utredning, utan en politisk pamflett utan ­eftertanke. Privatisering av universitet hotar både oberoendet, forskningskvaliteten och samhällsnyttan, skriver 36 forskare vid svenska högskolor och universitet.

  • 3.
    Audusseau, Helene
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Implications of a temperature increase for host plant range: predictions for a butterfly2013In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 3, no 9, p. 3021-3029Article in journal (Refereed)
    Abstract [en]

    Although changes in phenology and species associations are relatively well-documented responses to global warming, the potential interactions between these phenomena are less well understood. In this study, we investigate the interactions between temperature, phenology (in terms of seasonal timing of larval growth) and host plant use in the polyphagous butterfly Polygonia c-album. We found that the hierarchy of larval performance on three natural host plants was not modified by a temperature increase as such. However, larval performance on each host plant and temperature treatment was affected by rearing season. Even though larvae performed better at the higher temperature regardless of the time of the rearing, relative differences between host plants changed with the season. For larvae reared late in the season, performance was always better on the herbaceous plant than on the woody plants. In this species, it is likely that a prolonged warming will lead to a shift from univoltinism to bivoltinism. The demonstrated interaction between host plant suitability and season means that such a shift is likely to lead to a shift in selective regime, favoring specialization on the herbaceous host. Based on our result, we suggest that host range evolution in response to temperature increase would in this species be highly contingent on whether the population undergoes a predicted shift from one to two generations. We discuss the effect of global warming on species associations and the outcome of asynchrony in rates of phenological change.

  • 4.
    Audusseau, Hélène
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Paris-Est Créteil University, France.
    Celorio-Mancera, Maria de la Paz
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Why stay in a bad relationship? The effect of local host phenology on a generalist butterfly feeding on a low-ranked host2016In: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 16, article id 144Article in journal (Refereed)
    Abstract [en]

    Background: In plant-feeding insects, the evolutionary retention of polyphagy remains puzzling. A better understanding of the relationship between these organisms and changes in the metabolome of their host plants is likely to suggest functional links between them, and may provide insights into how polyphagy is maintained. Results: We investigated the phenological change of Cynoglossum officinale, and how a generalist butterfly species, Vanessa cardui, responded to this change. We used untargeted metabolite profiling to map plant seasonal changes in both primary and secondary metabolites. We compared these data to differences in larval performance on vegetative plants early and late in the season. We also performed two oviposition preference experiments to test females' ability to choose between plant developmental stages (vegetative and reproductive) early and late in the season. We found clear seasonal changes in plant primary and secondary metabolites that correlated with larval performance. The seasonal change in plant metabolome reflected changes in both nutrition and toxicity and resulted in zero survival in the late period. However, large differences among families in larval ability to feed on C. officinale suggest that there is genetic variation for performance on this host. Moreover, females accepted all plants for oviposition, and were not able to discriminate between plant developmental stages, in spite of the observed overall differences in metabolite profile potentially associated with differences in suitability as larval food. Conclusions: In V. cardui, migratory behavior, and thus larval feeding times, are not synchronized with plant phenology at the reproductive site. This lack of synchronization, coupled with the observed lack of discriminatory oviposition, obviously has potential fitness costs. However, this opportunistic behavior may as well function as a source of potential host plant evolution, promoting for example the acceptance of new plants.

  • 5.
    Audusseau, Hélène
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Paris-Est Créteil University, France.
    Le Vaillant, Maryline
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Karlsson, Bengt
    Stockholm University, Faculty of Science, Department of Zoology.
    Schmucki, Reto
    Species range expansion constrains the ecological niches of resident butterflies2017In: Journal of Biogeography, ISSN 0305-0270, E-ISSN 1365-2699, Vol. 44, no 1, p. 28-38Article in journal (Refereed)
    Abstract [en]

    Aim: Changes in community composition resulting from environmental changes modify biotic interactions and affect the distribution and density of local populations. Such changes are currently occurring in nettle-feeding butterflies in Sweden where Araschnia levana has recently expanded its range northward and is now likely to interact with resident species (Aglais urticae and Aglais io). Butterfly occurrence data collected over years and across regions enabled us to investigate how a recent range expansion of A. levana may have affected the environmental niche of resident species.

    Location: We focused on two regions of Sweden (Skane and Norrstrom) where A. levana has and has not established and two time periods (2001-2006 and 2009-2012) during its establishment in Skane.

    Methods: We performed two distinct analyses in each region using the PCA-env and the framework described in Broennimann etal. (2012). First, we described the main sources of variation in the environment. Second, in each time period and region, we characterized the realized niches of our focal species across topographic and land use gradients. Third, we quantified overlaps and differences in realized niches between and within species over time.

    Results: In Skane, A. levana has stabilized its distribution over time, while the distribution of the native species has shifted. These shifts depicted a consistent pattern of avoiding overlap between the native species and the environmental space occupied by A. levana, and it was stronger for A. urticae than for A. io. In both regions, we also found evidence of niche partitioning between native species.

    Main conclusions: Interspecific interactions are likely to affect local species distributions. It appears that the ongoing establishment of A. levana has modified local biotic interactions and induced shifts in resident species distributions. Among the mechanisms that can explain such patterns of niche partitioning, parasitoid-driven apparent competition may play an important role in this community.

  • 6.
    Bergström, Anders
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Putting more eggs in the best basket: clutch size regulation in the comma butterfly2006In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 31, no 3, p. 255-260Article in journal (Refereed)
    Abstract [en]

    1. Many studies have identified different factors influencing clutchsize regulation, primarily within various groups of insects. One prediction is that ovipositing females should increase clutch size with host quality. However, in many studies it is not clear whether ovipositing females are responding to host quality or quantity.

    2. Females of the polyphagous comma butterfly, allowed to oviposit on two hosts differing greatly in quality: the preferred host, stinging nettle (Polygonia c-album (L.), wereUrtica dioica L.), and the low-ranked host, birch (Betula pubescens  Ehrh). Ovipositing females were observed visually and clutch sizes were recorded. The experiment was repeated in three different years; in total, 938 observations of oviposition events were made.

    3. In all three years, females ovipositing on (median 1.6–1.85) compared with females ovipositing on 1.0–1.3) three years were pooled.

    4. Thus, on better hosts. It is suggested that the proximate mechanism is likely to be a response to the same stimuli used for female ranking of host plants in the preference hierarchy. U. dioica laid larger clutchesB. pubescens (median. The difference was significant in two out of three years and when allP. c-album females exhibit clutch-size regulation, with larger clutches

  • 7. Blanckenhorn, Wolf U
    et al.
    Dixon, Anthony FG
    Fairbairn, Daphne J
    Foellmer, Matthias W
    Gibert, Patricia
    van der Linde, Kim
    Meier, Rudolf
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Pitnick, Scott
    Schoff, Christopher
    Signorelli, Martino
    Teder, Tiit
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Proximate causes of Rensch's rule: Does sexual size dimorphism in arthropods result from sex differences in development time?2007In: American Naturalist, Vol. 169, no 2, p. 245-257Article in journal (Refereed)
    Abstract [en]

    A prominent interspecific pattern of sexual size dimorphism (SSD) is Rensch's rule, according to which male body size is more variable or evolutionarily divergent than female body size. Assuming equal growth rates of males and females, SSD would be entirely mediated, and Rensch's rule proximately caused, by sexual differences in development times, or sexual bimaturism (SBM), with the larger sex developing for a proportionately longer time. Only a subset of the seven arthropod groups investigated in this study exhibits Rensch's rule. Furthermore, we found only a weak positive relationship between SSD and SBM overall, suggesting that growth rate differences between the sexes are more important than development time differences in proximately mediating SSD in a wide but by no means comprehensive range of arthropod taxa. Except when protandry is of selective advantage ( as in many butterflies, Hymenoptera, and spiders), male development time was equal to ( in water striders and beetles) or even longer than ( in drosophilid and sepsid flies) that of females. Because all taxa show female-biased SSD, this implies faster growth of females in general, a pattern markedly different from that of primates and birds (analyzed here for comparison). We discuss three potential explanations for this pattern based on life-history trade-offs and sexual selection.

  • 8.
    Braga, Mariana P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Araujo, Sabrina B. L.
    Agosta, Salvatore
    Brooks, Daniel
    Hoberg, Eric
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Boeger, Walter A.
    Host use dynamics in a heterogeneous fitness landscape generates oscillations in host range and diversification2018In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 72, no 9, p. 1773-1783Article in journal (Refereed)
    Abstract [en]

    Colonization of novel hosts is thought to play an important role in parasite diversification, yet little consensus has been achieved about the macroevolutionary consequences of changes in host use. Here, we offer a mechanistic basis for the origins of parasite diversity by simulating lineages evolved in silico. We describe an individual-based model in which (i) parasites undergo sexual reproduction limited by genetic proximity, (ii) hosts are uniformly distributed along a one-dimensional resource gradient, and (iii) host use is determined by the interaction between the phenotype of the parasite and a heterogeneous fitness landscape. We found two main effects of host use on the evolution of a parasite lineage. First, the colonization of a novel host allowed parasites to explore new areas of the resource space, increasing phenotypic and genotypic variation. Second, hosts produced heterogeneity in the parasite fitness landscape, which led to reproductive isolation and therefore, speciation. As a validation of the model, we analyzed empirical data from Nymphalidae butterflies and their host plants. We then assessed the number of hosts used by parasite lineages and the diversity of resources they encompass. In both simulated and empirical systems, host diversity emerged as the main predictor of parasite species richness.

  • 9.
    Braga, Mariana P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Guimarães Jr, Paulo R.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Unifying host-associated diversification processes using butterfly-plant networks2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 5155Article in journal (Refereed)
    Abstract [en]

    Explaining the exceptional diversity of herbivorous insects is an old problem in evolutionary ecology. Here we focus on the two prominent hypothesised drivers of their diversification, radiations after major host switch or variability in host use due to continuous probing of new hosts. Unfortunately, current methods cannot distinguish between these hypotheses, causing controversy in the literature. Here we present an approach combining network and phylogenetic analyses, which directly quantifies support for these opposing hypotheses. After demonstrating that each hypothesis produces divergent network structures, we then investigate the contribution of each to diversification in two butterfly families: Pieridae and Nymphalidae. Overall, we find that variability in host use is essential for butterfly diversification, while radiations following colonisation of a new host are rare but can produce high diversity. Beyond providing an important reconciliation of alternative hypotheses for butterfly diversification, our approach has potential to test many other hypotheses in evolutionary biology.

  • 10.
    Braga, Mariana P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Landis, Michael
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Ronquist, Fredrik
    Bayesian analysis of host repertoire evolutionManuscript (preprint) (Other academic)
  • 11.
    Braga, Mariana P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Landis, Michael
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Ronquist, Fredrik
    Evolution of butterfly-plant networks revealed by Bayesian inference of host repertoireManuscript (preprint) (Other academic)
  • 12.
    Cassel-Lundhagen, Anna
    et al.
    SLU, Uppsala.
    Tammaru, Toomas
    Tartu University, Estland.
    Windig, Jack J
    Wageningen University, Nederländerna.
    Ryrholm, Nils
    Högskolan i Gävle.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Are peripheral populations special? Congruent patterns in two butterfly species2009In: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 32, no 4, p. 591-600Article in journal (Refereed)
    Abstract [en]

    Populations at range margins may be genetically different from more central ones for a number of mutually non-exclusive reasons. Specific selection pressures may operate in environments that are more marginal for the species. Genetic drift may also have a strong effect in these populations if they are small, isolated and/or have experienced significant bottlenecks during the colonisation phase. The question if peripheral populations are special, and if yes then how and why, is of obvious relevance for speciation theory, as well as for conservation biology. To evaluate the uniqueness of populations at range margins and the influence of gene flow and selection, we performed a morphometric study of two grassland butterfly species: Coenonympha arcania and C. hero (Lepidoptera: Nymphalidae). The samples were collected from Swedish populations that are peripheral and isolated from the main area of the species distributions and from populations in the Baltic states that are peripheral but connected to the main area of the species distributions. These samples were compared to those from central parts of the species distributions. The isolated populations in both species differed consistently from both peripheral and central populations in their wing size and shape. We interpret this as a result of selection caused by differences in population structure in these isolated locations, presumably favoring different dispersal propensity of these butterflies. Alternative explanations based on colonisation history, latitudinal effects, inbreeding or phenotypic plasticity appear less plausible. As a contrast, the much weaker and seemingly random among-region differences in wing patterns are more likely to be ascribed to weaker selection pressures allowing genetic drift to be influential. In conclusion, both morphological data and results from neutral genetic markers in earlier studies of the same system provide congruent evidence of both adaptation and genetic drift in the isolated Swedish populations of both species.

  • 13.
    Celorio-Mancera, Maria de la Paz
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Vogel, Heiko
    Söderlind, Lina
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Mechanisms of macroevolution: polyphagous plasticity in butterfly larvae revealed by RNA-Seq2013In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 22, no 19, p. 4884-4895Article in journal (Refereed)
    Abstract [en]

    Transcriptome studies of insect herbivory are still rare, yet studies in model systems have uncovered patterns of transcript regulation that appear to provide insights into how insect herbivores attain polyphagy, such as a general increase in expression breadth and regulation of ribosomal, digestion- and detoxification-related genes. We investigated the potential generality of these emerging patterns, in the Swedish comma, Polygonia c-album, which is a polyphagous, widely-distributed butterfly. Urtica dioica and Ribes uva-crispa are hosts of P. c-album, but Ribes represents a recent evolutionary shift onto a very divergent host. Utilizing the assembled transcriptome for read mapping, we assessed gene expression finding that caterpillar life-history (i.e. 2nd vs. 4th-instar regulation) had a limited influence on gene expression plasticity. In contrast, differential expression in response to host-plant identified genes encoding serine-type endopeptidases, membrane-associated proteins and transporters. Differential regulation of genes involved in nucleic acid binding was also observed suggesting that polyphagy involves large scale transcriptional changes. Additionally, transcripts coding for structural constituents of the cuticle were differentially expressed in caterpillars in response to their diet indicating that the insect cuticle may be a target for plant defence. Our results state that emerging patterns of transcript regulation from model species appear relevant in species when placed in an evolutionary context.

  • 14. Dalin, Peter
    et al.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Host-plant quality adaptively affects the diapause threshold: evidence from leaf beetles in willow plantations2012In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 37, no 6, p. 490-499Article in journal (Refereed)
    Abstract [en]

    1. Voltinism of herbivorous insects can vary depending on environmental conditions. The leaf beetle Phratora vulgatissima L. is univoltine in Sweden but will sometimes initiate a second generation in short-rotation coppice (SRC) willow plantations. 2. The study investigated whether increased voltinism by P. vulgatissima in plantations can be explained by (i) rapid life-cycle development allowing two generations, or (ii) postponed diapause induction on coppiced willows. 3. In the field, no difference was found in the phenology or development of first-generation broods between plantations (S. viminalis) and natural willow habitats (S. cinerea). However, the induction of diapause occurred 12 weeks later in SRC willow plantations. 4. Laboratory experiments indicated no genetic difference in the critical day-length for diapause induction between beetles originating from plantations and natural habitats. Development time was unaffected by host-plant quality but critical day-length was prolonged by almost an hour when the beetles were reared on a non-preferred willow species (S. phylicifolia). When reared on new leaves from re-sprouting shoots of recently coppiced willow plants, diapause incidence was significantly less than when the beetles were reared on mature leaves from uncoppiced plants. 5. The study suggests that P. vulgatissima has a plastic diapause threshold influenced by host-plant quality. The use of host-plant quality as a diapause-inducing stimulus is likely to be adaptive in cases where food resources are unpredictable, such as when new host-plant tissue is produced after a disturbance. SRC willows may allow two beetle generations due to longer growing seasons of coppiced plants that grow vigorously.

  • 15.
    de la Paz Celorio-Mancera, Maria
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Huss, Mikael
    Vezzi, Francesco
    Neethiraj, Ramprasad
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Reimegård, Johan
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Evolutionary history of host use, rather than plant phylogeny, determines gene expression in a generalist butterfly2016In: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 16, article id 59Article in journal (Refereed)
    Abstract [en]

    Background: Although most insect species are specialized on one or few groups of plants, there are phytophagous insects that seem to use virtually any kind of plant as food. Understanding the nature of this ability to feed on a wide repertoire of plants is crucial for the control of pest species and for the elucidation of the macroevolutionary mechanisms of speciation and diversification of insect herbivores. Here we studied Vanessa cardui, the species with the widest diet breadth among butterflies and a potential insect pest, by comparing tissue-specific transcriptomes from caterpillars that were reared on different host plants. We tested whether the similarities of gene-expression response reflect the evolutionary history of adaptation to these plants in the Vanessa and related genera, against the null hypothesis of transcriptional profiles reflecting plant phylogenetic relatedness. Result: Using both unsupervised and supervised methods of data analysis, we found that the tissue-specific patterns of caterpillar gene expression are better explained by the evolutionary history of adaptation of the insects to the plants than by plant phylogeny. Conclusion: Our findings suggest that V. cardui may use two sets of expressed genes to achieve polyphagy, one associated with the ancestral capability to consume Rosids and Asterids, and another allowing the caterpillar to incorporate a wide range of novel host-plants.

  • 16.
    Eriksson, Maertha
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Functional Morphology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Carlsson, Mikael A.
    Stockholm University, Faculty of Science, Department of Zoology, Functional Morphology.
    Insect brain plasticity: effects of olfactory input on neuropil size2019In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 6, no 8, article id 190875Article in journal (Refereed)
    Abstract [en]

    Insect brains are known to express a high degree of experience-dependent structural plasticity. One brain structure in particular, the mushroom body (MB), has been attended to in numerous studies as it is implicated in complex cognitive processes such as olfactory learning and memory. It is, however, poorly understood to what extent sensory input per se affects the plasticity of the mushroom bodies. By performing unilateral blocking of olfactory input on immobilized butterflies, we were able to measure the effect of passive sensory input on the volumes of antennal lobes (ALs) and MB calyces. We showed that the primary and secondary olfactory neuropils respond in different ways to olfactory input. ALs show absolute experience-dependency and increase in volume only if receiving direct olfactory input from ipsilateral antennae, while MB calyx volumes were unaffected by the treatment and instead show absolute age-dependency in this regard. We therefore propose that cognitive processes related to behavioural expressions are needed in order for the calyx to show experience-dependent volumetric expansions. Our results indicate that such experience-dependent volumetric expansions of calyces observed in other studies may have been caused by cognitive processes rather than by sensory input, bringing some causative clarity to a complex neural phenomenon.

  • 17. Esperk, Toomas
    et al.
    Tammaru, Toomas
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Intraspecific variability in the number of larval instars in insects2007In: J. Economic Entomology, Vol. 100, p. 627-646Article in journal (Refereed)
    Abstract [en]

    The number of larval instars varies widely across insect species. Although in star number is frequently considered to be invariable within species, intraspecific variability in the number of instars is not an exceptional phenomenon. However, the knowledge has remained fragmentary, and there are no recent attempts to synthesize the results of relevant studies. Based on published case studies, we show that intraspecific variability in the number of larval instars is widespread across insect taxa, occurring in most major orders, in both hemimetabolous and holometabolous insects. We give an overview of various factors that have been observed to affect the number of instars. Temperature, photoperiod, food quality and quantity, humidity, rearing density, physical condition, inheritance, and sex are the most common factors influencing the number of instars. We discuss adaptive scenarios that may provide ultimate explanations for the plasticity in instar number. The data available largely support the compensation scenario, according to which instar number increases in adverse conditions when larvae fail to reach a species-specific threshold size for metamorphosis. However, in Orthoptera and Coleoptera, there are some exceptional species in which instar number is higher in favorable conditions. In more specific cases, the adaptive value of the variability in instar number may be in reaching or maintaining the developmental stage adapted to hibernation, producing additional generations in multivoltine species, or increasing the probability of surviving in long-lasting adverse conditions.

  • 18. Esperk, Toomas
    et al.
    Tammaru, Toomas
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Teder, Tiit
    Achieving high sexual dimorphism: insects add instars2007In: Ecological Entomology, Vol. 32, p. 243-256Article in journal (Refereed)
    Abstract [en]

    1. In arthropods, the evolution of sexual size dimorphism (SSD) may be constrained by a physiological limit on growth within each particular larval instar. A high SSD could, however, be attained if the larvae of the larger sex pass through a higher number of larval instars.

    2. Based on a survey of published case studies, the present review shows that sex-related difference in the number of instars is a widespread phenomenon among insects. In the great majority of species with a sexually dimorphic instar number, females develop through a higher number of instars than males.

    3. Female-biased sexual dimorphism in final sizes in species with sexually dimorphic instar number was found to considerably exceed a previously estimated median value of SSD for insects in general. This suggests a causal connection between high female-biased SSD, and additional instars in females. Adding an extra instar to larval development allows an insect to increase its adult size at the expense of prolonged larval development.

    4. As in the case of additional instars, SSD is fully formed late in ontogeny, larval growth schedules and imaginal sizes can be optimised independently. No conflict between selective pressures operating in juvenile and adult stages is therefore expected.

    5. In most species considered, the number of instars also varied within the sexes. Phenotypic plasticity in instar number may thus be a precondition for a sexual difference in instar number to evolve.

  • 19.
    Gamberale-Stille, Gabriella
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Schäpers, Alexander
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Selective attention by priming in host search behavior of 2 generalist butterflies2019In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 30, no 1, p. 142-149Article in journal (Refereed)
    Abstract [en]

    We show that females of 2 generalist butterflies improve their search efficacy after previous encounters of the same host in a way similar to search-image formation, especially if the butterfly-host relationship is historically old. Thus, by targeting a single host at a time, host search efficacy may be improved and constitute a selection pressure for specialization. This result can help explain the evolutionary trend toward host specialization in phytophagous insects that is not well understood. Abstract In phytophagous insects such as butterflies, there is an evolutionary trend toward specialization in host plant use. One contributing mechanism for this pattern may be found in female host search behavior. Since search attention is limited, generalist females searching for hosts for oviposition may potentially increase their search efficacy by aiming their attention on a single host species at a time, a behavior consistent with search image formation. Using laboratory reared and mated females of 2 species of generalist butterflies, the comma, Polygonia c-album, and the painted lady, Vanessa cardui (Lepidoptera: Nymphalidae), we investigated the probability of finding a specific target host (among nonhost distractors) immediately after being primed with an oviposition experience of the same host as compared with different host in indoor cages. We used species-specific host plants that varied with respect to growth form, historical age of the butterfly-host association, and relative preference ranking. We found improved search efficacy after previous encounters of the same host for some but not all host species. Positive priming effects were found only in hosts with which the butterfly has a historically old relationship and these hosts are sometimes also highly preferred. Our findings provides additional support for the importance of behavioral factors in shaping the host range of phytophagous insects, and show that butterflies can attune their search behavior to compensate for negative effects of divided attention between multiple hosts.

  • 20.
    Gamberale-Stille, Gabriella
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Söderlind, Lina
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Host plant choice in the comma butterfly-larval choosiness may ameliorate effects of indiscriminate oviposition2014In: Insect Science, ISSN 1672-9609, E-ISSN 1744-7917, Vol. 21, no 4, p. 499-506Article in journal (Refereed)
    Abstract [en]

    In most phytophagous insects, the larval diet strongly affects future fitness and in species that do not feed on plant parts as adults, larval diet is the main source of nitrogen. In many of these insect host plant systems, the immature larvae are considered to be fully dependent on the choice of the mothers, who, in turn, possess a highly developed host recognition system. This circumstance allows for a potential mother-offspring conflict, resulting in the female maximizing her fecundity at the expense of larval performance on suboptimal hosts. In two experiments, we aimed to investigate this relationship in the polyphagous comma butterfly, Polygonia c-album, by comparing the relative acceptance of low- and medium-ranked hosts between females and neonate larvae both within individuals between life stages, and between mothers and their offspring. The study shows a variation between females in oviposition acceptance of low-ranked hosts, and that the degree of acceptance in the mothers correlates with the probability of acceptance of the same host in the larvae. We also found a negative relationship between stages within individuals as there was a higher acceptance of lower ranked hosts in females who had abandoned said host as a larva. Notably, however, neonate larvae of the comma butterfly did not unconditionally accept to feed from the least favorable host species even when it was the only food source. Our results suggest the possibility that the disadvantages associated with a generalist oviposition strategy can be decreased by larval participation in host plant choice.

  • 21.
    Gotthard, Karl
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Individual state controls temperature dependence in a butterfly (Lasiommata maera)2000In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 267, no 1443, p. 589-93Article in journal (Refereed)
    Abstract [en]

    In ectotherms there is typically a strong and positive correlation between growth rate and ambient temperature when food is not limiting. However, the exact relationship between growth rate and temperature varies among populations in many species. As a consequence, it has been suggested that selection for a rapid increase in growth rate with temperature should be stronger in populations experiencing a high degree of time-stress, compared with populations experiencing little time-stress. In the present study we take this adaptive hypothesis further and investigate if variation in time-stress among individuals of a single population may affect the relationship between growth rate and ambient temperature. Time-stress was manipulated by rearing larvae of the butterfly Lasiommata maera in different day-length regimes. The results show that individuals experiencing a higher degree of time-stress increase their growth rates more in higher temperatures compared with individuals under less time-stress. Hence, the adaptive hypothesis was supported and the relationship between growth rate and temperature was highly state dependent. These findings may be of general importance for understanding the evolution of life histories in seasonal environments.

  • 22.
    Heidel-Fischer, Hanna
    et al.
    Department of Entomology, Max Planck Institute for Chemical Ecology.
    Freitak, Dalial
    Department of Entomology, Max Planck Institute for Chemical Ecology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Soderlind, Lina
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Vogel, Heiko
    Department of Entomology, Max Planck Institute for Chemical Ecology.
    Nylin, Soren
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Phylogenetic relatedness and host plant growth form influence gene expression of the polyphagous comma butterfly (Polygonia c-album).2009In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 10, no 1, p. 506-Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: BACKGROUND: The mechanisms that shape the host plant range of herbivorous insect are to date not well understood but knowledge of these mechanisms and the selective forces that influence them can expand our understanding of the larger ecological interaction. Nevertheless, it is well established that chemical defenses of plants influence the host range of herbivorous insects. While host plant chemistry is influenced by phylogeny, also the growth forms of plants appear to influence the plant defense strategies as first postulated by Feeny (the "plant apparency" hypothesis). In the present study we aim to investigate the molecular basis of the diverse host plant range of the comma butterfly (Polygonia c-album) by testing differential gene expression in the caterpillars on three host plants that are either closely related or share the same growth form. RESULTS: In total 120 differentially expressed genes were identified in P. c-album after feeding on different host plants, 55 of them in the midgut and 65 in the restbody of the caterpillars. Expression patterns could be confirmed with an independent method for 14 of 27 tested genes. Pairwise similarities in upregulation in the midgut of the caterpillars were higher between plants that shared either growth form or were phylogenetically related. No known detoxifying enzymes were found to be differently regulated in the midgut after feeding on different host plants. CONCLUSIONS: Our data suggest a complex picture of gene expression in response to host plant feeding. While each plant requires a unique gene regulation in the caterpillar, both phylogenetic relatedness and host plant growth form appear to influence the expression profile of the polyphagous comma butterfly, in agreement with phylogenetic studies of host plant utilization in butterflies.

  • 23.
    Hill, Jason
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics. Uppsala University, Sweden.
    Rastas, Pasi
    Hornett, Emily A.
    Neethiraj, Ramprasad
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Clark, Nathan
    Morehouse, Nathan
    de la Paz Celorio-Mancera, Maria
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Carnicer Cols, Jofre
    Dircksen, Heinrich
    Stockholm University, Faculty of Science, Department of Zoology, Functional Morphology.
    Meslin, Camille
    Keehnen, Naomi
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Pruisscher, Peter
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Sikkink, Kristin
    Vives, Maria
    Vogel, Heiko
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Woronik, Alyssa
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics. New York University, USA.
    Boggs, Carol L.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Unprecedented reorganization of holocentric chromosomes provides insights into the enigma of lepidopteran chromosome evolution2019In: Science Advances, E-ISSN 2375-2548, Vol. 5, no 6, article id eaau3648Article in journal (Refereed)
    Abstract [en]

    Chromosome evolution presents an enigma in the mega-diverse Lepidoptera. Most species exhibit constrained chromosome evolution with nearly identical haploid chromosome counts and chromosome-level gene collinearity among species more than 140 million years divergent. However, a few species possess radically inflated chromosomal counts due to extensive fission and fusion events. To address this enigma of constraint in the face of an exceptional ability to change, we investigated an unprecedented reorganization of the standard lepidopteran chromosome structure in the green-veined white butterfly (Pieris napi). We find that gene content in P. napi has been extensively rearranged in large collinear blocks, which until now have been masked by a haploid chromosome number close to the lepidopteran average. We observe that ancient chromosome ends have been maintained and collinear blocks are enriched for functionally related genes suggesting both a mechanism and a possible role for selection in determining the boundaries of these genome-wide rearrangements.

  • 24.
    Janz, Niklas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Braga, Mariana P
    Stockholm University, Faculty of Science, Department of Zoology.
    Wahlberg, Niklas
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    On oscillations and flutterings - A reply to Hamm and Fordyce2016In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 5, p. 1150-1155Article in journal (Refereed)
    Abstract [en]

    The diversification of plant-feeding insects is seen as a spectacular example of evolutionary radiation. Hence, developing hypotheses to explain this diversification, and methods to test them, is an important undertaking. Some years ago, we presented the oscillation hypothesis as a general process that could drive diversification of this and similar interactions, through repeated expansions and contractions of host ranges. Hamm and Fordyce recently presented a study with the outspoken intention of testing this hypothesis where they concluded that the oscillation hypothesis was not supported. We point out several problems with their study, owing both to a misrepresentation of our hypothesis and to the methods. We provide a clarifying description of the oscillation hypothesis, and detail some predictions that follow from it. A reanalysis of the data demonstrated a troubling sensitivity of the "SSE" class of models to small changes in model specification, and we caution against using them for tests of trait-based diversification. Future tests of the hypothesis also need to better acknowledge the processes behind the host range oscillations. We suspect that doing so will resolve some of the apparent conflicts between our hypothesis and the view presented by Hamm and Fordyce.

  • 25.
    Janz, Niklas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution. Ekologi.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology. Ekologi.
    The oscillation hypothesis of host-plant range and speciation2008In: Specialization, speciation and radiation: the evolutionary biology of herbivorous insects, Berkeley: University of California Press, 2008, p. 203-215Chapter in book (Refereed)
  • 26.
    Janz, Niklas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Wahlberg, Niklas
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk ekologi.
    Diversity begets diversity: host expansions and the diversification of plant-feeding insects.2006In: BMC Evol Biol, ISSN 1471-2148, Vol. 6, no 1, p. 4-Article in journal (Refereed)
    Abstract [en]

    Background: Plant-feeding insects make up a large part of earth's total biodiversity. While it has been shown that herbivory has repeatedly led to increased diversification rates in insects, there has been no compelling explanation for how plant-feeding has promoted speciation rates. There is a growing awareness that ecological factors can lead to rapid diversification and, as one of the most prominent features of most insect-plant interactions, specialization onto a diverse resource has often been assumed to be the main process behind this diversification. However, specialization is mainly a pruning process, and is not able to actually generate diversity by itself. Here we investigate the role of host colonizations in generating insect diversity, by testing if insect speciation rate is correlated with resource diversity.

    Results: By applying a variant of independent contrast analysis, specially tailored for use on questions of species richness (MacroCAIC), we show that species richness is strongly correlated with diversity of host use in the butterfly family Nymphalidae. Furthermore, by comparing the results from reciprocal sister group selection, where sister groups were selected either on the basis of diversity of host use or species richness, we find that it is likely that diversity of host use is driving species richness, rather than vice versa.

    Conclusion: We conclude that resource diversity is correlated with species richness in the Nymphalidae and suggest a scenario based on recurring oscillations between host expansions – the incorporation of new plants into the repertoire – and specialization, as an important driving force behind the diversification of plant-feeding insects.

  • 27.
    Janz, Niklas
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology. Stockholm University, Faculty of Humanities, Centre for the Study of Cultural Evolution.
    Söderlind, Lina
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology. Stockholm University, Faculty of Science, Department of Zoology, Department of Animal Ecology.
    No effect of larval experience on adult host preferences in Polygonia c-album (Lepidoptera: Nymphalidae): on the persistence of Hopkins' host selection principle2009In: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 34, no 1, p. 50-57Article in journal (Refereed)
    Abstract [en]

    1. The possible effect of juvenile imprinting or 'chemical legacy' on the subsequent oviposition - often called the 'Hopkins' host selection principle' - has been a controversial but recurrent theme in the literature on host-plant preference. While it appears possible in principle, experimental support for the hypothesis is equivocal. The present study points out that it is also important to consider its theoretical implications, and asks under what circumstances, if any, it should be favoured by natural selection.

    2. Following this reasoning, it is predicted that host preference in the polyphagous butterfly Polygonia c-album L. (Lepidoptera, Nymphalidae) should not be influenced by larval environment. This was tested by rearing larvae on three natural host plants: the high-ranked Urtica dioica and the medium-ranked Salix cinerea and Ribes uva-crispa, and exposing the naive females to oviposition choices involving the same set of plants.

    3. It was found that larval host plant had no effect on oviposition decisions of the adult female. Hence, the Hopkins' host selection principle does not seem to be applicable in this species.

    4. Based on recent insights on how accuracy of environmental versus genetic information should affect the control of developmental switches, the conditions that could favour the use of juvenile cues in oviposition decisions are discussed. Although the Hopkins' host selection hypothesis cannot be completely ruled out, we argue that the circumstances required for it to be adaptive are so specific that it should not be invoked as a general hypothesis for host selection in plant-feeding insects.

     

  • 28.
    Keehnen, Naomi
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Fors, Lisa
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Järver, Peter
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Spetz, Anna-Lena
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Theopold, Ulrich
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Wheat, Christopher
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Geographic variation in hemocyte diversity and phagocytic propensity shows a diffuse genomic signature in the green veined white butterflyManuscript (preprint) (Other academic)
    Abstract [en]

    Insects rely on their innate immune system to successfully mediate complex interactions with their internal microbiota, as well as the microbes present in the environment. Given the variation in microbes across habitats, the challenges to respond to them is likely to result in local adaptation in the immune system. Here we focus upon phagocytosis, a mechanism by which pathogens and foreign particles are engulfed in order to be contained, killed and processed for antigen presentation. We investigated the phenotypic and genetic variation related to phagocytosis, in two allopatric populations of the butterfly Pieris napi. We found that the populations differ in their hemocyte composition, and overall phagocytic capability, driven by the increased phagocytic propensity of each cell type. However, no evidence for divergence in phagocytosis-related genes was observed, though an enrichment of genes involved in glutamine metabolism was found, which have recently been linked to immune cell differentiation in mammals.

  • 29.
    Keehnen, Naomi L. P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hill, Jason
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Microevolutionary selection dynamics acting on immune genes of the green-veined white butterfly, Pieris napi2018In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 27, no 13, p. 2807-2822Article in journal (Refereed)
    Abstract [en]

    Insects rely on their innate immune system to successfully mediate complex interactions with their microbiota, as well as the microbes present in the environment. Previous work has shown that components of the canonical immune gene repertoire evolve rapidly and have evolutionary characteristics originating from interactions with fast-evolving microorganisms. Although these interactions are likely to vary among populations, there is a poor understanding of the microevolutionary dynamics of immune genes, especially in non-Dipteran insects. Here, we use the full set of canonical insect immune genes to investigate microevolutionary dynamics acting on these genes between and among populations by comparing three allopatric populations of the green-veined white butterfly, Pieris napi (Linne; Lepidoptera, Pieridae). Immune genes showed increased genetic diversity compared to genes from the rest of the genome and various functional categories exhibited different types of signatures of selection, at different evolutionary scales, presenting a complex pattern of selection dynamics. Signatures of balancing selection were identified in 10 genes, and 17 genes appear to be under positive selection. Genes involved with the cellular arm of the immune response as well as the Toll pathway appear to be enriched among our outlier loci, regardless of functional category. This suggests that the targets of selection might focus upon an entire pathway, rather than functional subsets across pathways. Our microevolutionary results are similar to previously observed macroevolutionary patterns from diverse taxa, suggesting that either the immune system is robust to dramatic differences in life history and microbial communities, or that diverse microbes exert similar selection pressures.

  • 30.
    Keehnen, Naomi L. P.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    Kučerova, Lucie
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. Biology Centre CAS, Czech Republic.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Theopold, Ulrich
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology, Population Genetics.
    The consequences of surviving infection across the metamorphic boundary: tradeoff insights from RNAseq and life history measuresManuscript (preprint) (Other academic)
    Abstract [en]

    The broad diversity of insect life has been shaped, in part, by pathogen pressure, yet the influence of injury and infection during critical periods of development is understudied. During development, insects undergo metamorphosis, wherein the organism experiences a dramatic shift in their overall morphology, and physiology. In temperate zones, metamorphosis is often directly followed by a developmental arrest called diapause, for which the insect needs to acquire enough energy reserves before the onset of winter. We investigated the long-term effects of injury and infection using two bacteria in the butterfly Pieris napi, revealing that the negative consequences of bacterial infection carry across the metamorphic boundary. Initial direct effects of infection were weight loss and slower development, as well as an increased mortality at higher infection levels. The detrimental effects were stronger in the gram-positive Micrococcus luteus compared to gram-negative Escherichia coli. Transcriptome-wide differences between the two bacteria were already observed in the gene expression profile of the first 24 hours after infection. Larvae infected with M. luteus showed a strong suppression of all non-immunity related processes, with several types of immune responses being activated. The impact of these transcriptomic changes, a tradeoff between homeostasis and immune response, were visible in the life history data, wherein individuals infected with M. luteus had the highest mortality rate, along with the lowest pupal weight, developmental rate and adult weight of all the treatments. Overall, we find that the cost of infection and wounding in the final larval instar carries over the metamorphic boundary, and is expected to negatively affect their lifetime fitness.

  • 31.
    Kodandaramaiah, Ullasa
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Peña, Carlos
    Stockholm University, Faculty of Science, Department of Zoology.
    Braby, Michael F.
    Grund, Roger
    Müller, Chris J.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wahlberg, Niklas
    Phylogenetics of Coenonymphina (Nymphalidae Satyrinae) and the problem of rooting rapid radiations2010In: Molecular Phylogenetics and Evolution, ISSN 1055-7903, E-ISSN 1095-9513, Vol. 54, no 2, p. 386-394Article in journal (Refereed)
    Abstract [en]

    We report a rapid radiation of a group of butterflies within the family Nymphalidae and examine some aspects of popular analytical methods in dealing with rapid radiations. We attempted to infer the phylogeny of butterflies belonging to the subtribe Coenonymphina sensu lato using five genes (4398bp) with Maximum Parsimony, Maximum Likelihood and Bayesian analyses. Initial analyses suggested that the group has undergone rapid speciation within Australasia. We further analyzed the dataset with different outgroup combinations the choice of which had a profound effect on relationships within the ingroup. Modelling methods recovered Coenonymphina as a monophyletic group to the exclusion of Zipaetis and Orsotriaena, irrespective of outgroup combination. Maximum Parsimony occasionally returned a polyphyletic Coenonymphina, with Argyronympha grouping with outgroups, but this was strongly dependent on the outgroups used. We analyzed the ingroup without any outgroups and found that the relationships inferred among taxa were different from those inferred when either of the outgroup combinations was used, and this was true for all methods. We also tested whether a hard polytomy is a better hypothesis to explain our dataset, but could not find conclusive evidence. We therefore conclude that the major lineages within Coenonymphina form a near-hard polytomy with regard to each other. The study highlights the importance of testing different outgroups rather than using results from a single outgroup combination of a few taxa, particularly in difficult cases where basal nodes appear to receive low support. We provide a revised classification of Coenonymphina; Zipaetis and Orsotriaena are transferred to the tribe Eritina.

  • 32.
    Kodandaramaiah, Ullasa
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Weingartner, Elisabet
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Dalén, L.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Population structure in relation to host-plant ecology and Wolbachia infestation in the comma butterfly2011In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 24, no 10, p. 2173-2185Article in journal (Refereed)
    Abstract [en]

    Experimental work on Polygonia c-album, a temperate polyphagous butterfly species, has shown that Swedish, Belgian, Norwegian and Estonian females are generalists with respect to host-plant preference, whereas females from UK and Spain are specialized on Urticaceae. Female preference is known to have a strong genetic component. We test whether the specialist and generalist populations form respective genetic clusters using data from mitochondrial sequences and 10 microsatellite loci. Results do not support this hypothesis, suggesting that the specialist and generalist traits have evolved more than once independently. Mitochondrial DNA variation suggests a rapid expansion scenario, with a single widespread haplotype occurring in high frequency, whereas microsatellite data indicate strong differentiation of the Moroccan population. Based on a comparison of polymorphism in the mitochondrial data and sequences from a nuclear gene, we show that the diversity in the former is significantly less than that expected under neutral evolution. Furthermore, we found that almost all butterfly samples were infected with a single strain of Wolbachia, a maternally inherited bacterium. We reason that indirect selection on the mitochondrial genome mediated by a recent sweep of Wolbachia infection has depleted variability in the mitochondrial sequences. We also surmise that P. c-album could have expanded out of a single glacial refugium and colonized Morocco recently.

  • 33.
    Kodandaramaiah, Ullasa
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Weingartner, Elisabet
    Stockholm University, Faculty of Science, Department of Botany.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Leski, Michael
    Slove, Jessica
    Stockholm University, Faculty of Science, Department of Zoology.
    Warren, Andrew
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Investigating concordance among genetic data, subspecies circumscriptions and hostplant use in the nymphalid butterfly polygonia faunus2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 7, p. e41058-Article in journal (Refereed)
    Abstract [en]

    Subspecies are commonly used taxonomic units to formally describe intraspecific geographic variation in morphological traits. However, the concept of subspecies is not clearly defined, and there is little agreement about what they represent in terms of evolutionary units, and whether they can be used as reliably useful units in conservation, evolutionary theory and taxonomy. We here investigate whether the morphologically well-characterized subspecies in the North American butterfly Polygonia faunus are supported by genetic data from mitochondrial sequences and eight microsatellite loci. We also investigate the phylogeographic structure of P. faunus and test whether similarities in host-plant use among populations are related to genetic similarity. Neither the nuclear nor the mitochondrial data corroborated subspecies groupings. We found three well defined genetic clusters corresponding to California, Arizona and (New Mexico+Colorado). There was little structuring among the remaining populations, probably due to gene flow across populations. We found no support for the hypothesis that similarities in host use are related to genetic proximity. The results indicate that the species underwent a recent rapid expansion, probably from two glacial refugia in western North America. The mitochondrial haplotype network indicates at least two independent expansion phases into eastern North America. Our results clearly demonstrate that subspecies in P. faunus do not conform to the structuring of genetic variation. More studies on insects and other invertebrates are needed to better understand the scope of this phenomenon. The results of this study will be crucial in designing further experiments to understand the evolution of hostplant utilization in this species.

  • 34.
    Kubrak, Olga I.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Kucerova, Lucie
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Theopold, Ulrich
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Nässel, Dick R.
    Stockholm University, Faculty of Science, Department of Zoology.
    Characterization of Reproductive Dormancy in Male Drosophila melanogaster2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, article id 572Article in journal (Refereed)
    Abstract [en]

    Insects are known to respond to seasonal and adverse environmental changes by entering dormancy, also known as diapause. In some insect species, including Drosophila melanogaster, dormancy occurs in the adult organism and postpones reproduction. This adult dormancy has been studied in female flies where it is characterized by arrested development of ovaries, altered nutrient stores, lowered metabolism, increased stress and immune resistance and drastically extended lifespan. Male dormancy, however, has not been investigated in D. melanogaster, and its physiology is poorly known in most insects. Here we show that unmated 3-6 h old male flies placed at low temperature (11 degrees C) and short photoperiod (10 Light:14 Dark) enter a state of dormancy with arrested spermatogenesis and development of testes and male accessory glands. Over 3 weeks of diapause we see a dynamic increase in stored carbohydrates and an initial increase and then a decrease in lipids. We also note an up-regulated expression of genes involved in metabolism, stress responses and innate immunity. Interestingly, we found that male flies that entered reproductive dormancy do not attempt to mate females kept under non-diapause conditions (25 degrees C, 1 2L:1 2D), and conversely non-diapausing males do not mate females in dormancy. In summary, our study shows that male D. melanogaster can enter reproductive dormancy. However, our data suggest that dormant male flies deplete stored nutrients faster than females, studied earlier, and that males take longer to recover reproductive capacity after reintroduction to non-diapause conditions.

  • 35.
    Kubrak, Olga I.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Flatt, Thomas
    Nässel, Dick R.
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Adaptation to fluctuating environments in a selection experiment with Drosophila melanogaster2017In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 7, no 11, p. 3796-3807Article in journal (Refereed)
    Abstract [en]

    A fundamental question in life-history evolution is how organisms cope with fluctuating environments, including variation between stressful and benign conditions. For short-lived organisms, environments commonly vary between generations. Using a novel experimental design, we exposed wild-derived Drosophila melanogaster to three different selection regimes: one where generations alternated between starvation and benign conditions, and starvation was always preceded by early exposure to cold; another where starvation and benign conditions alternated in the same way, but cold shock sometimes preceded starvation and sometimes benign conditions; and a third where conditions were always benign. Using six replicate populations per selection regime, we found that selected flies increased their starvation resistance, most strongly for the regime where cold and starvation were reliably combined, and this occurred without decreased fecundity or extended developmental time. The selected flies became stress resistant, displayed a pronounced increase in early life food intake and resource storage. In contrast to previous experiments selecting for increased starvation resistance in D. melanogaster, we did not find increased storage of lipids as the main response, but instead that, in particular for females, storage of carbohydrates was more pronounced. We argue that faster mobilization of carbohydrates is advantageous in fluctuating environments and conclude that the phenotype that evolved in our experiment corresponds to a compromise between the requirements of stressful and benign environments.

  • 36.
    Kucerova, Lucie
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Kubrak, Olga I.
    Stockholm University, Faculty of Science, Department of Zoology.
    Bengtsson, Jonas M.
    Stockholm University, Faculty of Science, Department of Zoology.
    Strnad, Hynek
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Theopold, Ulrich
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Nässel, Dick R.
    Stockholm University, Faculty of Science, Department of Zoology.
    Slowed aging during reproductive dormancy is reflected in genome-wide transcriptome changes in Drosophila melanogaster2016In: BMC Genomics, ISSN 1471-2164, E-ISSN 1471-2164, Vol. 17, article id 50Article in journal (Refereed)
    Abstract [en]

    Background: In models extensively used in studies of aging and extended lifespan, such as C. elegans and Drosophila, adult senescence is regulated by gene networks that are likely to be similar to ones that underlie lifespan extension during dormancy. These include the evolutionarily conserved insulin/IGF, TOR and germ line-signaling pathways. Dormancy, also known as dauer stage in the larval worm or adult diapause in the fly, is triggered by adverse environmental conditions, and results in drastically extended lifespan with negligible senescence. It is furthermore characterized by increased stress resistance and somatic maintenance, developmental arrest and reallocated energy resources. In the fly Drosophila melanogaster adult reproductive diapause is additionally manifested in arrested ovary development, improved immune defense and altered metabolism. However, the molecular mechanisms behind this adaptive lifespan extension are not well understood. Results: A genome wide analysis of transcript changes in diapausing D. melanogaster revealed a differential regulation of more than 4600 genes. Gene ontology (GO) and KEGG pathway analysis reveal that many of these genes are part of signaling pathways that regulate metabolism, stress responses, detoxification, immunity, protein synthesis and processes during aging. More specifically, gene readouts and detailed mapping of the pathways indicate downregulation of insulin-IGF (IIS), target of rapamycin (TOR) and MAP kinase signaling, whereas Toll-dependent immune signaling, Jun-N-terminal kinase (JNK) and Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways are upregulated during diapause. Furthermore, we detected transcriptional regulation of a large number of genes specifically associated with aging and longevity. Conclusions: We find that many affected genes and signal pathways are shared between dormancy, aging and lifespan extension, including IIS, TOR, JAK/STAT and JNK. A substantial fraction of the genes affected by diapause have also been found to alter their expression in response to starvation and cold exposure in D. melanogaster, and the pathways overlap those reported in GO analysis of other invertebrates in dormancy or even hibernating mammals. Our study, thus, shows that D. melanogaster is a genetically tractable model for dormancy in other organisms and effects of dormancy on aging and lifespan.

  • 37.
    Larsdotter-Mellström, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Western Australia, Australia.
    Eriksson, Kerstin
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Carlsson, Mikael A.
    Stockholm University, Faculty of Science, Department of Zoology.
    Male butterflies use an anti-aphrodisiac pheromone to tailor ejaculates2016In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 30, no 2, p. 255-261Article in journal (Refereed)
    Abstract [en]

    When females mate with multiple partners, the risk of sperm competition depends on female mating history. To maximize fitness, males should adjust their mating investment according to this risk. In polyandrous butterflies, males transfer a large, nutritious ejaculate at mating. Larger ejaculates delay female remating and confer an advantage in sperm competition. We test whether male ejaculate size in the butterfly Pieris napi (Lepidoptera) varies with female mating history and thus sperm competition, and whether males assess sperm competition using the male-transferred anti-aphrodisiac methyl salicylate (MeS) as a cue. Both sexes responded physiologically to MeS in a dose-dependent manner. Males, however, were more sensitive to MeS than females. Ejaculates transferred by males mating with previously mated females were on average 26% larger than ejaculates transferred by males mating with virgin females, which conforms to sperm competition theory and indicates that males tailored their reproductive investment in response to sperm competition. Furthermore, ejaculates transferred by males mating with virgin females with artificially added MeS were also 26% larger than ejaculates transferred to control virgin females. Male-transferred anti-aphrodisiac pheromone not only functions as a male deterrent, but also carries information on female mating history and thus allows males to assess sperm competition.

  • 38.
    Larsdotter-Mellström, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. The University of Western Australia, Australia.
    Eriksson, Kerstin
    Liblikas, Ilme
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Borg-Karlsson, Anna K.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Janz, Niklas
    Stockholm University, Faculty of Science, Department of Zoology.
    Carlsson, Mikael A.
    Stockholm University, Faculty of Science, Department of Zoology.
    It's All in the Mix: Blend-Specific Behavioral Response to a Sexual Pheromone in a Butterfly2016In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 7, article id 68Article in journal (Refereed)
    Abstract [en]

    Among insects, sexual pheromones are typically mixtures of two to several components, all of which are generally required to elicit a behavioural response. Here we show for the first time that a complete blend of sexual pheromone components is needed to elicit a response also in a butterfly. Males of the Green-veined White, Pieris napi, emit an aphrodisiac pheromone, citral, from wing glands. This pheromone is requisite for females to accept mating with a courting male. Citral is a mixture of the two geometric isomers geranial (E-isomer) and neral (Z-isomer) in an approximate 1:1 ratio. We found that both these compounds are required to elicit acceptance behaviour, which indicates synergistic interaction between processing of the isomers. Using functional Ca2+ imaging we found that geranial and neral evoke significantly different but overlapping glomerular activity patterns in the antennal lobe, which suggests receptors with different affinity for the two isomers. However, these glomeruli were intermingled with glomeruli responding to ,for example, plant-related compounds, i.e. no distinct subpopulation of pheromone-responding glomeruli as in moths and other insects. In addition, these glomeruli showed lower specificity than pheromone-activated glomeruli in moths. We could, however, not detect any mixture interactions among four identified glomeruli, indicating that the synergistic effect may be generated at a higher processing level. Furthermore, correlations between glomerular activity patterns evoked by the single isomers and the blend did not change over time.

  • 39.
    Lehmann, Philipp
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Carlsson, Mikael A.
    Stockholm University, Faculty of Science, Department of Zoology.
    Idiosyncratic development of sensory structures in brains of diapausing butterfly pupae: implications for information processing2017In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 284, no 1858, article id 20170897Article in journal (Refereed)
    Abstract [en]

    Diapause is an important escape mechanism from seasonal stress in many insects. A certain minimum amount of time in diapause is generally needed in order for it to terminate. The mechanisms of time-keeping in diapause are poorly understood, but it can be hypothesized that a well-developed neural system is required. However, because neural tissue is metabolically costly to maintain, there might exist conflicting selective pressures on overall brain development during diapause, on the one hand to save energy and on the other hand to provide reliable information processing during diapause. We performed the first ever investigation of neural development during diapause and non-diapause (direct) development in pupae of the butterfly Pieris napi from a population whose diapause duration is known. The brain grew in size similarly in pupae of both pathways up to 3 days after pupation, when development in the diapause brain was arrested. While development in the brain of direct pupae continued steadily after this point, no further development occurred during diapause until temperatures increased far after diapause termination. Interestingly, sensory structures related to vision were remarkably well developed in pupae from both pathways, in contrast with neuropils related to olfaction, which only developed in direct pupae. The results suggest that a well-developed visual system might be important for normal diapause development.

  • 40.
    Lehmann, Philipp
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pruisscher, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Kostal, Vladimir
    Moos, Martin
    Simek, Petr
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Agren, Rasmus
    Varemo, Leif
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Metabolome dynamics of diapause in the butterfly Pieris napi: distinguishing maintenance, termination and post-diapause phases2018In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 221, no 2, article id UNSP jeb169508Article in journal (Refereed)
    Abstract [en]

    Diapause is a deep resting stage facilitating temporal avoidance of unfavourable environmental conditions, and is used by many insects to adapt their life cycle to seasonal variation. Although considerable work has been invested in trying to understand each of the major diapause stages (induction, maintenance and termination), we know very little about the transitions between stages, especially diapause termination. Understanding diapause termination is crucial for modelling and predicting spring emergence and winter physiology of insects, including many pest insects. In order to gain these insights, we investigated metabolome dynamics across diapause development in pupae of the butterfly Pieris napi, which exhibits adaptive latitudinal variation in the length of endogenous diapause that is uniquely well characterized. By employing a time-series experiment, we show that the whole-body metabolome is highly dynamic throughout diapause and differs between pupae kept at a diapause-terminating (low) temperature and those kept at a diapause-maintaining (high) temperature. We showmajor physiological transitions through diapause, separate temperature-dependent from temperature-independent processes and identify significant patterns of metabolite accumulation and degradation. Together, the data show that although the general diapause phenotype (suppressed metabolism, increased cold tolerance) is established in a temperature-independent fashion, diapause termination is temperature dependent and requires a cold signal. This revealed several metabolites that are only accumulated under diapause-terminating conditions and degraded in a temperature-unrelated fashion during diapause termination. In conclusion, our findings indicate that some metabolites, in addition to functioning as cryoprotectants, for example, are candidates for having regulatory roles as metabolic clocks or time-keepers during diapause.

  • 41.
    Lehmann, Philipp
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pruisscher, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Posledovich, Diana
    Stockholm University, Faculty of Science, Department of Zoology.
    Carlsson, Mikael
    Stockholm University, Faculty of Science, Department of Zoology.
    Käkelä, Reijo
    Tang, Patrik
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Energy and lipid metabolism during direct and diapause development in a pierid butterfly2016In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 219, no 19, p. 3049-3060Article in journal (Refereed)
    Abstract [en]

    Diapause is a fundamental component of the life-cycle in the majority of insects living in environments characterized by strong seasonality. The present study addresses poorly understood associations and trade-offs between endogenous diapause duration, thermal sensitivity of development, energetic cost of development and cold tolerance. Diapause intensity, metabolic rate trajectories and lipid profiles of directly developing and diapausing animals were studied using pupae and adults of Pieris napi butterflies from a population for which endogenous diapause is well studied. Endogenous diapause was terminated after 3 months and termination required chilling. Metabolic and postdiapause development rates increased with diapause duration, while the metabolic cost of postdiapause development decreased, indicating that once diapause is terminated development proceeds at a low rate even at low temperature. Diapausing pupae had larger lipid stores than the directly developing pupae and lipids constituted the primary energy source during diapause. However, during diapause lipid stores did not decrease. Thus, despite lipid catabolism meeting the low energy costs of the diapausing pupae, primary lipid store utilization did not occur until the onset of growth and metamorphosis in spring. In line with this finding, diapausing pupae contained low amounts of mitochondria-derived cardiolipins, which suggests a low capacity for fatty acid β-oxidation. While ontogenic development had a large effect on lipid and fatty acid profiles, only small changes in these were seen during diapause. The data therefore indicate that the diapause lipidomic phenotype is built early, when pupae are still at high temperature, and retained until diapause post-diapause development.

  • 42.
    Lehmann, Philipp
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Van der Bijl, Wouter
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Timing of diapause termination in relation to variation in winter climate2017In: Physiological entomology (Print), ISSN 0307-6962, E-ISSN 1365-3032, Vol. 42, no 3, p. 232-238Article in journal (Refereed)
    Abstract [en]

    In temperate insects, winters are typically endured by entering diapause, which comprises a deep resting stage. Correct timing of diapause termination is vital for synchronization of emergence with conspecifics and for mobilizing resources when conditions for growth and reproduction become favourable. Although critical to survival, the intrinsic and extrinsic drivers of diapause termination timing are poorly understood. In the present study, we investigate diapause development under a range of durations (10-24weeks) spent at different temperatures (-2 to 10 degrees C) in the pupal diapausing butterfly Pieris napi Linnaeus (Lepidoptera: Pieridae). We determine: (i) the maximum cold temperature for diapause development; (ii) if pupae in diapause count cold days or cold sums; and (iii) whether diapause termination is distinct or gradual. The results indicate large and idiosyncratic effects of high and low nonlethal temperatures on diapause development in P. napi. Although all temperatures tested lead to diapause termination, a thermal optimum between 2 and 4 degrees C is observed. Lower temperatures lead to decreased eclosion propensity, whereas higher temperatures slow down development and increase emergence desynchronization. These data suggest that, rather than a simple cold-summing process with a distinct diapause termination point, there are trade-offs between time and temperature at the low and high end of the thermal range, resulting in a nonlinear thermal landscape showing a ridge of increasing eclosion propensity at moderate temperatures. The present study suggests that the effects of temperature on diapause development should be included in projections on post-winter phenology models of insects, including pest species.

  • 43.
    Lindestad, Olle
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Analyzing the neutral and adaptive background of butterfly voltinism reveals structural variation in a core circadian geneManuscript (preprint) (Other academic)
    Abstract [en]

    Many insects exhibit geographic variation in voltinism, the number of generations produced per year. This includes high-latitude species in previously glaciated areas, implying divergent selection on life cycle traits during or shortly after recent colonization. Here, we use a whole-genome approach to genetically characterize a set of populations of the butterfly Pararge aegeria that differ in voltinism. We construct a high-quality de novo genome for P. aegeria, and assess genome-wide genetic diversity and differentiation between populations. We then use the inferred phylogeographic relationships as the basis for a scan for loci showing signs of divergent selection associated with voltinism differences. The genic outliers detected include population-specific mutations of circadian loci, most notably a locally fixed 97-amino acid deletion in the circadian gene timeless. Variation in timeless has previously been implicated as underlying variation in life cycle regulation in wild populations in our study species, as well as in other insects. These results add to a growing body of research framing circadian gene variation as a mechanism for generating local adaptation of life cycles.

  • 44.
    Lindestad, Olle
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Context-dependent candidate genes: a test of within-population genetic variation for photoperiodic plasticityManuscript (preprint) (Other academic)
    Abstract [en]

    Components of the circadian clock have been implicated as involved in photoperiodic regulation of diapause across various insect groups, hence contributing to adaptation to adverse seasonal conditions. Such studies typically involve either characterization of nondiapause mutants, or comparisons of populations differing in diapause induction thresholds, leaving within-population variation unexplored. Here, we present a test of the effects on diapause induction of within-population variation at two circadian loci, timeless and period, in the butterfly Pararge aegeria. Variation at both loci has previously shown to be associated with diapause induction on an interpopulation level. However, in the present study, no effect on induction was found of either locus at a within-population level. Examination of sequence data revealed novel variation at both timeless and period in the studied population. We hypothesize that selection for a northern-type life cycle may have promoted compensatory variants, ensuring a high rate of diapause induction despite the presence of southern, diapause-averting SNP alleles. Additionally, both timeless and period showed considerable variation across Scandinavian populations, with an unusually high rate of nonsynonymous substitutions compared to the rest of the genome, raising new questions about the fine-scale adaptive dynamics of circadian genes.

  • 45.
    Lindestad, Olle
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Local adaptation of photoperiodic plasticity maintains life cycle variation within latitudes in a butterfly2019In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 100, no 1, article id e02550Article in journal (Refereed)
    Abstract [en]

    The seasonal cycle varies geographically and organisms are under selection to express life cycles that optimally exploit their spatiotemporal habitats. In insects, this often means producing an annual number of generations (voltinism) appropriate to the local season length. Variation in voltinism may arise from variation in environmental factors (e.g., temperature or photoperiod) acting on a single reaction norm shared across populations, but it may also result from local adaptation of reaction norms. However, such local adaptation is poorly explored at short geographic distances, especially within latitudes. Using a combination of common-garden rearing and life cycle modeling, we have investigated the causal factors behind voltinism variation in Swedish populations of the butterfly Pararge aegeria, focusing on a set of populations that lie within a single degree of latitude but nonetheless differ in season length and voltinism. Despite considerable differences in ambient temperature between populations, modeling suggested that the key determinant of local voltinism was in fact interpopulation differences in photoperiodic response. These include differences in the induction thresholds for winter diapause, as well as differences in photoperiodic regulation of larval development, a widespread but poorly studied phenomenon. Our results demonstrate previously neglected ways that photoperiodism may mediate insect phenological responses to temperature, and emphasize the importance of local adaptation in shaping phenological patterns in general, as well as for predicting the responses of populations to changes in climate.

  • 46. Macgregor, Callum J.
    et al.
    Thomas, Chris D.
    Roy, David B.
    Beaumont, Mark A.
    Bell, James R.
    Brereton, Tom
    Bridle, Jon R.
    Dytham, Calvin
    Fox, Richard
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Hoffmann, Ary A.
    Martin, Geoff
    Middlebrook, Ian
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Platts, Philip J.
    Rasteiro, Rita
    Saccheri, Ilik J.
    Villoutreix, Romain
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Hill, Jane K.
    Climate-induced phenology shifts linked to range expansions in species with multiple reproductive cycles per year2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 4455Article in journal (Refereed)
    Abstract [en]

    Advances in phenology (the annual timing of species' life-cycles) in response to climate change are generally viewed as bioindicators of climate change, but have not been considered as predictors of range expansions. Here, we show that phenology advances combine with the number of reproductive cycles per year (voltinism) to shape abundance and distribution trends in 130 species of British Lepidoptera, in response to similar to 0.5 degrees C spring-temperature warming between 1995 and 2014. Early adult emergence in warm years resulted in increased within- and between-year population growth for species with multiple reproductive cycles per year (n = 39 multivoltine species). By contrast, early emergence had neutral or negative consequences for species with a single annual reproductive cycle (n = 91 univoltine species), depending on habitat specialisation. We conclude that phenology advances facilitate pole-wards range expansions in species exhibiting plasticity for both phenology and voltinism, but may inhibit expansion by less flexible species.

  • 47. Midega, Charles A. O.
    et al.
    Khan, Zeyaur R.
    Pickett, John A.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Host plant selection behaviour of Chilo partellus and its implication for effectiveness of a trap crop2011In: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 138, no 1, p. 40-47Article in journal (Refereed)
    Abstract [en]

    Female lepidopterans can display a hierarchy of preference among potential host species, a trait thought to arise from the balance between attractants and deterrents to which the insects respond. Host plant ranking by moths and larvae of Chilo partellus Swinhoe (Lepidoptera: Crambidae), an important pest of cereals in Africa, was investigated, and whether eggs deposited on specific host plants yield larvae of particular host preferences. Trap plants are used in management of this pest. However, any 'disagreement' in host ranking between moths and larvae could potentially reduce effectiveness of trap crops as larvae emigrate to the main crop from the parent's preferred trap plant. We also investigated whether host plant preference is influenced by the diet upon which larvae fed as part of an integrated assessment of the relationship between host plant selection and learning in C. partellus. Five host plants (all Poaceae) were used: maize (Zea mays L.), sorghum (Sorghum bicolor Moench), Napier grass (Pennisetum purpureum Schumach), and two varieties of signal grass [Brachiaria brizantha (A. Rich.) Stapf], viz., local (henceforth signal grass) and improved ('Mulato'). In multiple choice tests, C. partellus female moths preferentially oviposited on Napier grass, followed by sorghum, maize, and signal grass, and least preferred 'Mulato'. Larvae however equally orientated and settled on leaf cuts of maize, sorghum, signal grass, and Napier grass, but least preferred 'Mulato'. Moreover, eggs from specific host plants did not yield larvae of particular host preferences. Furthermore, oviposition preference was not altered by the larval food. These results imply only a slight 'disagreement' in host ranking behaviour between moths and larvae, which is beneficial for trap cropping as larvae would not 'reject' the trap plant and appreciably disperse to the neighboring plants. Moreover, absence of larval learning behaviour indicates that regardless of the larval food C. partellus moths would still be attracted to the selected trap plant.

  • 48. Mozuraitis, Raimondas
    et al.
    Radziute, Sandra
    Apsegaite, Violeta
    Cravcenco, Alexei
    Buda, Vincas
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Volatiles released from foliar extract of host plant enhance landing rates of gravid Polygonia c-album females, but do not stimulate oviposition2016In: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 158, no 3, p. 275-283Article in journal (Refereed)
    Abstract [en]

    The role of olfactory cues for host search is much less investigated in day-active butterflies than in their relatives, the nocturnal moths. The goal of this study was to investigate whether host-plant volatiles from foliar extracts of hop, Humulus lupulus L. (Cannabaceae), evoke electroantennographic (EAG) responses, increase landing rates, and stimulate egg-laying behavior of gravid Polygonia c-album L. (Lepidoptera: Nymphalidae) females. Eighty-nine volatile compounds were detected in a non-concentrated methanol extract of hop by gas chromatography-mass spectrometry, 11 of which elicited an EAG response. Concentration of the crude extract significantly reduced landing rates on artificial leaves treated with the sample due to loss of volatile compounds, but after landing the oviposition response of gravid females was not affected. A mixture of eight commercially available EAG-active volatiles increased the landing rate of gravid females to their source but did not act as oviposition stimulants. Dividing the volatile compounds into two groups - consisting of (1) hexanal, (E)-2-hexenal, octanal, nonanal, and decanal, and (2) sulcatone, humulene, and benzyl alcohol - obliterated effectiveness, revealing synergism between compounds. Although volatiles did not stimulate oviposition, they significantly contributed to the distribution of eggs by increasing the landing rates on treated artificial leaves.

  • 49.
    Neethiraj, Ramprasad
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    de la Paz Celorio-Mancera, Maria
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher
    Stockholm University, Faculty of Science, Department of Zoology.
    Investigating cis-regulatory variation within and between populations reveals significant enrichment of genes in central metabolismManuscript (preprint) (Other academic)
  • 50.
    Neethiraj, Ramprasad
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Nylin, Sören
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher
    Stockholm University, Faculty of Science, Department of Zoology.
    Holocentric chromosomes facilitate recombination and genetic variation in LepidopteraManuscript (preprint) (Other academic)
12 1 - 50 of 83
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf