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  • 1.
    Aalberg Haugen, Inger M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Berger, David
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    The evolution of alternative developmental pathways: footprints of selection on life-history traits in a butterfly2012In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 25, no 7, p. 1377-1388Article in journal (Refereed)
    Abstract [en]

    Developmental pathways may evolve to optimize alternative phenotypes across environments. However, the maintenance of such adaptive plasticity under relaxed selection has received little study. We compare the expression of life-history traits across two developmental pathways in two populations of the butterfly Pararge aegeria where both populations express a diapause pathway but one never expresses direct development in nature. In the population with ongoing selection on both pathways, the difference between pathways in development time and growth rate was larger, whereas the difference in body size was smaller compared with the population experiencing relaxed selection on one pathway. This indicates that relaxed selection on the direct pathway has allowed life-history traits to drift towards values associated with lower fitness when following this pathway. Relaxed selection on direct development was also associated with a higher degree of genetic variation for protandry expressed as within-family sexual dimorphism in growth rate. Genetic correlations for larval growth rate across sexes and pathways were generally positive, with the notable exception of correlation estimates that involved directly developing males of the population that experienced relaxed selection on this pathway. We conclude that relaxed selection on one developmental pathway appears to have partly disrupted the developmental regulation of life-history trait expression. This in turn suggests that ongoing selection may be responsible for maintaining adaptive developmental regulation along alternative developmental pathways in these populations.

  • 2.
    Aalberg Haugen, Inger M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Diapause induction and relaxed selection on alternative developmental pathways in a butterfly2015In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 84, no 2, p. 464-472Article in journal (Refereed)
    Abstract [en]

    Seasonal phenotypic plasticity entails differential trait expression depending on the time of season. The facultative induction of winter diapause in temperate insects is a developmental switch mechanism often leading to differential expression in life-history traits. However, when there is a latitudinal shift from a bivoltine to univoltine life cycle, selection for pathway-specific expression is disrupted, which may allow drift towards less optimal trait values within the non-selected pathway. We use field- and experimental data from five Swedish populations of Pararge aegeria to investigate latitudinal variation in voltinism, local adaptation in the diapause switch and footprints of selection on pathway-specific regulation of life-history traits and sexual dimorphism in larval development. Field data clearly illustrated how natural populations gradually shift from bivoltinism to univoltinism as latitude increases. This was supported experimentally as the decrease in direct development at higher latitudes was accompanied by increasing critical daylengths, suggesting local adaptation in the diapause switch. The differential expression among developmental pathways in development time and growth rate was significantly less pronounced in univoltine populations. Univoltine populations showed no significant signs of protandry during larval development, suggesting that erosion of the direct development pathway under relaxed selection has led to the loss of its sex-specific modifications.

  • 3.
    Aalberg Haugen, Inger M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Latitudinal phenological adaptation: diapause induction and differentiation between alternative developmental pathways in a butterflyManuscript (preprint) (Other academic)
    Abstract [en]

    1. Seasonal phenotypic plasticity entails differential trait expression depending on the time of season. The facultative induction of winter diapause in temperate insects is a developmental switch mechanism often leading to differential expression in life history traits. However, when there is a latitudinal shift from a bivoltine to univoltine life cycle, selection for pathway-specific expression is disrupted, which may allow drift towards less optimal trait values within the non-selected pathway.

    2. We use field- and experimental data from five Swedish populations of Pararge aegeria to investigate latitudinal variation in voltinism, local adaptation in the diapause switch, and footprints of selection on pathway-specific regulation of life history traits and sexual dimorphism in larval development.

    3. Field data clearly illustrated how natural populations gradually shift from bivoltinism to univoltinism as latitude increases. This was supported experimentally as the decrease in direct development at higher latitudes was accompanied by increasing critical daylengths, suggesting local adaptation in the diapause switch.

    4. The differential expression among developmental pathways in development time and growth rate was significantly less pronounced in univoltine populations. Univoltine populations showed no significant signs of protandry during larval development, suggesting that erosion of the direct development pathway under relaxed selection has led to the loss of its sex-specific modifications.

  • 4.
    Aalberg Haugen, Inger M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    The development and expression of seasonal polyphenism in life-history traits in the butterfly Pararge aegeriaManuscript (preprint) (Other academic)
  • 5.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Divergence and ontogenetic coupling of larval behaviour and thermal reaction norms in three closely related butterflies2011In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 278, no 1703, p. 313-320Article in journal (Refereed)
    Abstract [en]

    Genetic trade-offs such as between generalist-specialist strategies can be masked by changes in compensatory processes involving energy allocation and acquisition which regulation depends on the state of the individual and its ecological surroundings. Failure to account for such state dependence may thus lead to misconceptions about the trade-off structure and nature of constraints governing reaction norm evolution. Using three closely related butterflies, we first show that foraging behaviours differ between species and change remarkably throughout ontogeny causing corresponding differences in the thermal niches experienced by the foraging larvae. We further predicted that thermal reaction norms for larval growth rate would show state-dependent variation throughout development as a result of selection for optimizing feeding strategies in the respective foraging niches of young and old larvae. We found substantial developmental plasticity in reaction norms that was species-specific and reflected the different ontogenetic niche shifts. Any conclusions regarding constraints on performance curves or species-differentiation in thermal physiology depend on when reaction norms were measured. This demonstrates that standardized estimates at single points in development, or in general, allow variation in only one ecological dimension, may sometimes provide incomplete information on reaction norm constraints.

  • 6.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Time stress, predation risk and diurnal-nocturnal foraging trade-offs in larval prey.2008In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 62, no 10, p. 1655-1663Article in journal (Refereed)
    Abstract [en]

    Insect larvae increase in size with several orders of magnitude throughout development making them more conspicuous to visually hunting predators. This change in predation pressure is likely to impose selection on larval anti-predator behaviour and since the risk of detection is likely to decrease in darkness, the night may offer safer foraging opportunities to large individuals. However, forsaking day foraging reduces development rate and could be extra costly if prey are subjected to seasonal time stress. Here we test if size-dependent risk and time constraints on feeding affect the foraging–predation risk trade-off expressed by the use of the diurnal–nocturnal period. We exposed larvae of one seasonal and one non-seasonal butterfly to different levels of seasonal time stress and time for diurnal–nocturnal feeding by rearing them in two photoperiods. In both species, diurnal foraging ceased at large sizes while nocturnal foraging remained constant or increased, thus larvae showed ontogenetic shifts in behaviour. Short night lengths forced small individuals to take higher risks and forage more during daytime, postponing the shift to strict night foraging to later on in development. In the non-seasonal species, seasonal time stress had a small effect on development and the diurnal–nocturnal foraging mode. In contrast, in the seasonal species, time for pupation and the timing of the foraging shift were strongly affected. We argue that a large part of the observed variation in larval diurnal–nocturnal activity and resulting growth rates is explained by changes in the cost/benefit ratio of foraging mediated by size-dependent predation and time stress.

  • 7.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Uppsala University, Sweden.
    Olofsson, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Stockholm University, Faculty of Science, Department of Zoology. University of California Santa Cruz, USA.
    Karlsson, Bengt
    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.
    Intraspecific variation in body size and the rate of reproduction in female insects- adaptive allometry or biophysical constraint?2012In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 81, no 6, p. 1244-1258Article in journal (Refereed)
    Abstract [en]

    1. A high rate of reproduction may be costly if ecological factors limit immediate reproductive output as a fast metabolism compromises own future survival. Individuals with more reserves need more time and opportunity to realize their reproductive potential. Theory therefore predicts that the reproductive rate, defined as the investment in early reproduction in proportion to total potential, should decrease with body size within species. 2. However, metabolic constraints on body size- and temperature-dependent biological rates may impede biophysical adaptation. Furthermore, the sequential manner resources that are allocated to somatic vs. reproductive tissue during ontogeny may, when juveniles develop in unpredictable environments, further contribute to non-adaptive variation in adult reproductive rates. 3. With a model on female egg laying in insects, we demonstrate how variation in body reserves is predicted to affect reproductive rate under different ecological scenarios. Small females always have higher reproductive rates but shorter lifespans. However, incorporation of female host selectivity leads to more similar reproductive rates among female size classes, and oviposition behaviour is predicted to co-evolve with reproductive rate, resulting in small females being more selective in their choice and gaining relatively more from it. 4. We fed simulations with data on the butterfly Pararge aegeria to compare model predictions with reproductive rates of wild butterflies. However, simulated reproductive allometry was a poor predictor of that observed. Instead, reproductive rates were better explained as a product of metabolic constraints on rates of egg maturation, and an empirically derived positive allometry between reproductive potential and size. However, fitness is insensitive to moderate deviations in reproductive rate when oviposition behaviour is allowed to co-evolve in the simulations, suggesting that behavioural compensation may mitigate putative metabolic and developmental constraints. 5. More work is needed to understand how physiology and development together with compensatory behaviours interact in shaping reproductive allometry. Empirical studies should evaluate adaptive hypotheses against proper null hypotheses, including prediction from metabolic theory, preferentially by studying reproductive physiology in combination with behaviour. Conversely, inferences of constraint explanations on reproductive rates must take into consideration that adaptive scenarios may predict similar allometric exponents.

  • 8.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Olofsson, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Stockholm University, Faculty of Science, Department of Zoology.
    Ecological Constraints on Female Fitness in a Phytophagous Insect2012In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, no 4, p. 464-480Article in journal (Refereed)
    Abstract [en]

    Although understanding female reproduction is crucial for population demography, determining how and to what relative extent it is constrained by different ecological factors is complicated by difficulties in studying the links between individual behavior, life history, and fitness in nature. We present data on females in a natural population of the butterfly Leptidea sinapis. These data were combined with climate records and laboratory estimates of life-history parameters to predict the relative impact of different ecological constraints on female fitness in the wild. Using simulation models, we partitioned effects of male courtship, host plant availability, and temperature on female fitness. Results of these models indicate that temperature is the most constraining factor on female fitness, followed by host plant availability; the short-term negative effects of male courtship that were detected in the field study were less important in models predicting female reproductive success over the entire life span. In the simulations, females with more reproductive reserves were more limited by the ecological variables. Reproductive physiology and egg-laying behavior were therefore predicted to be co-optimized but reach different optima for females of different body sizes; this prediction is supported by the empirical data. This study thus highlights the need for studying behavioral and life-history variation in orchestration to achieve a more complete picture of both demographic and evolutionary processes in naturally variable and unpredictable environments.

  • 9.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Walters, Richard
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    What keeps insects small? - Size dependent predation on two species of butterfly larvae2006In: Evolutionary Ecology, ISSN 0269-7653, Vol. 20, no 6, p. 575-589Article in journal (Refereed)
    Abstract [en]

    Insect size usually increases greatly in the latter stages of development, while reproductive value increases strongly with adult size. Mechanisms that can balance the benefits associated with increased growth are poorly understood, raising the question: what keeps insects from becoming larger? If predation risk was to increase with juvenile size, it would make an extension of development very risky, favouring smaller final sizes. But field measures of juvenile mortality seldom show any general patterns of size dependence. We here therefore try to estimate a mechanistic relationship between juvenile size and predation risk by exposing the larvae of two closely related butterflies to a generalist invertebrate predator in a laboratory experiment. Predation risk increased with larval size but was not affected by the species-specific growth rate differences. These results indicate that predation risk may increase with the size of the juvenile even when predators are relatively small. By basing a model simulation on our data we also show that size dependent predation of the kind found in this study has potential to stabilise selection on body size in these species. Thus, these findings suggest that more detailed studies of the size dependence of predation risk on juvenile instars will increase the understanding of what it is that keeps insects small.

  • 10.
    Berger, David
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Walters, Richard
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    What limits insect fecundity? Body size- and temperature-dependent egg maturation and oviposition in a butterfly2008In: Functional Ecology, ISSN 0269-8463, Vol. 22, no 3, p. 523-529Article in journal (Refereed)
    Abstract [en]

    1. Large female insects usually have high potential fecundity. Therefore selection should favour an increase in body size given that these females get opportunities to realize their potential advantage by maturing and laying more eggs. However, ectotherm physiology is strongly temperature-dependent, and activities are carried out sufficiently only within certain temperature ranges. Thus it remains unclear if the fecundity advantage of a large size is fully realized in natural environments, where thermal conditions are limiting.

    2. Insect fecundity might be limited by temperature at two levels; first eggs need to mature, and then the female needs time for strategic ovipositing of the egg. Since a female cannot foresee the number of oviposition opportunities that she will encounter on a given day, the optimal rate of egg maturation will be governed by trade-offs associated with egg- and time-limited oviposition. As females of different sizes will have different amounts of body reserves, size-dependent allocation trade-offs between the mother's condition and her egg production might be expected.

    3. In the temperate butterfly Pararge aegeria, the time and temperature dependence of oviposition and egg maturation, and the interrelatedness of these two processes were investigated in a series of laboratory experiments, allowing a decoupling of the time budgets for the respective processes.

    4. The results show that realized fecundity of this species can be limited by both the temperature dependence of egg maturation and oviposition under certain thermal regimes. Furthermore, rates of oviposition and egg maturation seemed to have regulatory effects upon each other. Early reproductive output was correlated with short life span, indicating a cost of reproduction. Finally, large females matured more eggs than small females when deprived of oviposition opportunities. Thus, the optimal allocation of resources to egg production seems dependent on female size.

    5. This study highlights the complexity of processes underlying rates of egg maturation and oviposition in ectotherms under natural conditions. We further discuss the importance of temperature variation for egg- vs. time-limited fecundity and the consequences for the evolution of female body size in insects.

  • 11.
    Bergman, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Berger, David
    Stockholm University, Faculty of Science, Department of Zoology.
    Olofsson, Martin
    Stockholm University, Faculty of Science, Department of Zoology.
    Kemp, Darrell
    James Cook University, Australia.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Mating success of resident versus non-resident males in a territorial butterfly2007In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 274, no 1618, p. 1659-1665Article in journal (Refereed)
    Abstract [en]

    Male–male competition over territorial ownership suggests that winning is associated with considerable benefits. In the speckled wood butterfly, Pararge aegeria, males fight over sunspot territories on the forest floor; winners gain sole residency of a sunspot, whereas losers patrol the forest in search of females. It is currently not known whether residents experience greater mating success than nonresidents, or whether mating success is contingent on environmental conditions. Here we performed an experiment in which virgin females of P. aegeria were allowed to choose between a resident and a nonresident male in a large enclosure containing one territorial sunspot. Resident males achieved approximately twice as many matings as non-residents, primarily because matings were most often preceded by a female being discovered when flying through a sunspot. There was no evidence that territorial residents were more attractive per se, with females seen to reject them as often as nonresidents. Furthermore, in the cases where females were discovered outside of the sunspot, they were just as likely to mate with non-residents as residents. We hypothesize that the proximate advantage of territory ownership is that light conditions in a large sunspot greatly increase the male’s ability to detect and intercept passing receptive females.

  • 12.
    Bergman, Martin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Mate acquisition by females in a butterfly: the effects of mating status and age on female mate-locating behaviour2011In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 81, no 1, p. 225-229Article in journal (Refereed)
    Abstract [en]

    In most species, female reproductive success is determined by realized fecundity, which depends on the amount of female reproductive reserves and the availability of time for oviposition. Consequently, selection is likely to favour behaviour in virgin females that increases the likelihood of encountering males and thereby minimizing time without sperm. We used the speckled wood butterfly, Pararge aegeria, to test the hypothesis that virgin females increase the probability of encountering males by behaving more conspicuously. We also tested for an effect of age on behaviour, with the prediction that females behave more conspicuously if they remain unmated for a longer period. To do this we conducted controlled behavioural studies in large outdoor cages, comparing the behaviour of young and old, virgin and mated, females. We also assessed the time it took for a male to discover virgin versus mated females. Our results show an effect of age and mating status: old virgin females behaved more conspicuously than young virgin females and mated females, and spent more time in flight and performed more individual flights. Males also discovered virgin females faster than mated females. Furthermore, virgin females did not specifically locate the large sunspot, where perching males are found. Hence, females of P. aegeria adjust their behaviour in accordance with mating status and age, making them more likely to encounter a male and thereby maximize their reproductive success. This study underlines the importance of taking the distribution and behaviour of receptive females into account when studying mate-locating behaviour.

  • 13.
    Björkman, Christer
    et al.
    Swedish University for Agricultural Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Pettersson, Mats
    Swedish University for Agricultural Sciences.
    Body Size2009In: Encyclopedia of Insects / [ed] Vincent H. Resh, Ring T. Cardé, Amsterdam: Elsevier/Academic Press , 2009, 2, p. 114-116Chapter in book (Other academic)
  • 14. Chauvaud, Laurent
    et al.
    Patry, Yann
    Jolivet, Aurelie
    Cam, Emmanuelle
    Le Goff, Clement
    Strand, Oivind
    Charrier, Gregory
    Thebault, Julien
    Lazure, Pascal
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Clavier, Jacques
    Variation in size and growth of the great scallop pecten maximus along a latitudinal gradient2012In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 7, no 5, p. e37717-Article in journal (Refereed)
    Abstract [en]

    Understanding the relationship between growth and temperature will aid in the evaluation of thermal stress and threats to ectotherms in the context of anticipated climate changes. Most Pecten maximus scallops living at high latitudes in the northern hemisphere have a larger maximum body size than individuals further south, a common pattern among many ectotherms. We investigated differences in daily shell growth among scallop populations along the Northeast Atlantic coast from Spain to Norway. This study design allowed us to address precisely whether the asymptotic size observed along a latitudinal gradient, mainly defined by a temperature gradient, results from differences in annual or daily growth rates, or a difference in the length of the growing season. We found that low annual growth rates in northern populations are not due to low daily growth values, but to the smaller number of days available each year to achieve growth compared to the south. We documented a decrease in the annual number of growth days with age regardless of latitude. However, despite initially lower annual growth performances in terms of growing season length and growth rate, differences in asymptotic size as a function of latitude resulted from persistent annual growth performances in the north and sharp declines in the south. Our measurements of daily growth rates throughout life in a long-lived ectothermic species provide new insight into spatio-temporal variations in growth dynamics and growing season length that cannot be accounted for by classical growth models that only address asymptotic size and annual growth rate.

  • 15.
    Friberg, Magne
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Aalberg Haugen, Inger M.
    Stockholm University, Faculty of Science, Department of Zoology.
    Dahlerus, Josefin
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Asymmetric life-history decision-making in butterfly larvae2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 165, no 2, p. 301-310Article in journal (Refereed)
    Abstract [en]

    In temperate environments, insects appearing in several generations in the growth season typically have to decide during the larval period whether to develop into adulthood, or to postpone adult emergence until next season by entering a species-specific diapause stage. This decision is typically guided by environmental cues experienced during development. An early decision makes it possible to adjust growth rate, which would allow the growing larva to respond to time stress involved in direct development, whereas a last-minute decision would instead allow the larva to use up-to-date information about which developmental pathway is the most favourable under the current circumstances. We study the timing of the larval pathway decision-making between entering pupal winter diapause and direct development in three distantly related butterflies (Pieris napi, Araschnia levana and Pararge aegeria). We pinpoint the timing of the larval diapause decision by transferring larvae from first to last instars from long daylength (inducing direct development) to short daylength conditions (inducing diapause), and vice versa. Results show that the pathway decision is typically made in the late instars in all three species, and that the ability to switch developmental pathway late in juvenile life is conditional; larvae more freely switched from diapause to direct development than in the opposite direction. We contend that this asymmetry is influenced by the additional physiological preparations needed to survive the long and cold winter period, and that the reluctance to make a late decision to enter diapause has the potential to be a general trait among temperate insects.

  • 16. Gotthard, K.
    et al.
    Berger, D.
    Stockholm University, Faculty of Science, Department of Zoology.
    Walters, R
    What keeps insects small?: Time limitation during oviposition reduces the fecundity benefit of female size in a butterfly.2007In: American naturalist, Vol. 169, p. 768-779Article in journal (Refereed)
  • 17.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Adaptive growth decisions in butterflies2008In: Bioscience, ISSN 0006-3568, Vol. 58, no 3, p. 222-230Article in journal (Refereed)
    Abstract [en]

    Caterpillars have a great capacity for rapid weight gain, but to reap the benefits of this capacity, larvae must be able to survive in a hostile environment and emerge as adults at the right time of year. In this article, I review examples of growth decisions in butterfly larvae that can be viewed as adaptations for optimized growth performance. These include sex-specific growth decisions that lead to protandry and sexual size dimorphism, fine-tuning of growth in response to photoperiod and temperature, development of alternative larval morphs that mimic the plant structures they feed on, and the peculiar growth patterns of lycenid butterflies that manipulate ants and grow as "cuckoos" inside ant nests. I conclude that growth of an individual can be seen as the sum of several environmentally dependent decisions, which may influence the growth trajectory by changes in physiology, behavior, and morphology.

  • 18.
    Gotthard, Karl
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Berger, David
    Stockholm University, Faculty of Science, Department of Zoology.
    The diapause decision as a cascade switch for adaptive developmental plasticity in body mass in a butterfly.2010In: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 23, no 6, p. 1129-37Article in journal (Refereed)
    Abstract [en]

    Switch-induced developmental plasticity, such as the diapause decision in insects, is a major form of adaptation to variable environments. As individuals that follow alternative developmental pathways will experience different selective environments the diapause decision may evolve to a cascade switch that induces additional adaptive developmental differences downstream of the diapause decision. Here, we show that individuals following alternative developmental pathways in a Swedish population of the butterfly, Pararge aegeria, display differential optimization of adult body mass as a likely response to predictable differences in thermal conditions during reproduction. In a more northern population where this type of selection is absent no similar difference in adult mass among pathways was found. We conclude that the diapause decision in the southern population appears to act as a cascade switch, coordinating development downstream of the diapause decision, to produce adult phenotypes adapted to the typical thermal conditions of their expected reproductive period

  • 19.
    Gotthard, Karl
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Berger, David
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Bergman, Martin
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    Merilata, Sami
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology.
    The evolution of alternative morphs: density-dependent determination of larval colour dimorphism in a butterfly2009In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 98, no 2, p. 256-266Article in journal (Refereed)
    Abstract [en]

    Understanding the ultimate causes for the presence of polymorphisms within populations requires knowledge of how the expression of discrete morphs is regulated. In the present study, we explored the determination mechanism of a colour dimorphism in larvae of the butterfly Pararge xiphia (Satyrinae: Nymphalidae) with the ultimate aim of understanding its potential adaptive value. Last-instar larvae of P. xiphia develop into either a green or a brown morph, although all individuals are invariably green during the preceding three instars. A series of laboratory experiments reveal that morph development is strongly environmentally dependent and not the result of alternative alleles at one locus. Photoperiod, temperature, and in particular larval density, all influenced morph determination. The strong effect of a high larval density in inducing the brown morph parallels other known cases of density-dependent melanization in Lepidopteran larvae. Because melanization is often correlated with increased immune function, this type of determination mechanism is expected to be adaptive. However, the ecology and behaviour of P. xiphia larvae suggests that increased camouflage under high-density conditions may be an additional adaptive explanation. We conclude that the colour dimorphism of P. xiphia larvae is determined by a developmental threshold that is influenced both by heredity and by environmental conditions, and that selection for increased immune function and camouflage under high-density conditions may be responsible for maintaining the dimorphism. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 256–266.

  • 20.
    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.

  • 21.
    Kemp, Darrell
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology. Zoologisk Ekologi.
    Life history effects upon contest behaviour: Age as a predictor of territorial contest dynamics in two populations of the speckled wood butterfly, Pararge aegeria L.2006In: Ethology, ISSN 0179-1613, Vol. 112, no 5, p. 471-477Article in journal (Refereed)
    Abstract [en]

    Although empirical studies of life history effects upon sexually selected phenomena have largely overlooked contest behaviour, recent research suggests that territorial contest participation in butterflies may be mediated by ageing per se. Verbal and mathematical arguments predict lifetime increases in the expression of risky male reproductive behaviours, such as fighting, under a range of ecological conditions. Here we explored the relevance of ageing per se to contest dynamics in two phenologically distinct populations of the speckled wood butterfly, Pararge aegeria. We established 160 experimental like-population contests among naive south Swedish and Madeiran dyads, 112 of which we varied the age difference between combatants by 3-4 d. Although this age asymmetry did not influence contest outcome in either population, we found weak positive covariance between the loser's age and contest duration amongst Madeiran males. This is consistent with a slight lifetime increase in aggression because the duration of these aerial persistence contests is a sensitive measure of the losing male's level of aggressive intent. However, the size of this effect (semi-partial correlation = 0.281) suggests age is not as strongly relevant to contest behaviour in P. aegeria as in other territorial butterflies. We discuss the ways in which ecological differences between butterfly species, particularly with respect to predation risk, may have influenced the evolution of lifetime aggressive strategies in this group.

  • 22.
    Kivela, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Lehmann, Philipp
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Do respiratory limitations affect metabolism of insect larvae before moulting? An empirical test at the individual level2016In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 219, no 19, p. 3061-3071Article in journal (Refereed)
    Abstract [en]

    Recent data suggest that oxygen limitation may induce moulting in larval insects. This oxygen-dependent induction of moulting (ODIM) hypothesis stems from the fact that the tracheal respiratory system of insects grows primarily at moults, whereas tissue mass increases massively between moults. This may result in a mismatch between oxygen supply and demand at the end of each larval instar because oxygen demand of growing tissues exceeds the relatively fixed supply capacity of the respiratory system. The ODIM hypothesis predicts that, within larval instars, respiration and metabolic rates of an individual larva first increase with increasing body mass but eventually level off once the supply capacity of the tracheal system starts to constrain metabolism. Here, we provide the first individual-level test of this key prediction of the ODIM hypothesis. We use a novel methodology where we repeatedly measure respiration and metabolic rates throughout the penultimate- and final-instar larvae in the butterfly Pieris napi. In the penultimate instar, respiration and metabolic rates gradually decelerated along with growth, supporting the ODIM hypothesis. However, respiration and metabolic rates increased linearly during growth in the final instar, contradicting the prediction. Moreover, our data suggest considerable variation among individuals in the association between respiration rate and mass in the final instar. Overall, the results provide partial support for the ODIM hypothesis and suggest that oxygen limitation may emerge gradually within a larval instar. The results also suggest that there may be different moult induction mechanisms in larva-to-larva moults compared with the final metamorphic moult.

  • 23.
    Kivela, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Oulu.
    Valimaki, Panu
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    SEASONALITY MAINTAINS ALTERNATIVE LIFE-HISTORY PHENOTYPES2013In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 67, no 11, p. 3145-3160Article in journal (Refereed)
    Abstract [en]

    Many organisms express discrete alternative phenotypes (polyphenisms) in relation to predictable environmental variation. However, the evolution of alternative life-history phenotypes remains poorly understood. Here, we analyze the evolution of alternative life histories in seasonal environments by using temperate insects as a model system. Temperate insects express alternative developmental pathways of diapause and direct development, the induction of a certain pathway affecting fitness through its life-history correlates. We develop a methodologically novel and holistic simulation model and optimize development time, growth rate, body size, reproductive effort, and adult life span simultaneously in both developmental pathways. The model predicts that direct development should be associated with shorter development time (duration of growth) and adult life span, higher growth rate and reproductive effort, smaller body size as well as lower fecundity compared to the diapause pathway, because the two generations divide the available time unequally. These predictions are consistent with many empirical data. Our analysis shows that seasonality alone can explain the evolution of alternative life histories.

  • 24. Kivela, Sami M.
    et al.
    Viinamaki, Sonja
    Keret, Netta
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Hohtola, Esa
    Valimaki, Panu
    Elucidating mechanisms for insect body size: partial support for the oxygen-dependent induction of moulting hypothesis2018In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 221, no 2, article id UNSP jeb166157Article in journal (Refereed)
    Abstract [en]

    Body size is a key life history trait, and knowledge of its mechanistic basis is crucial in life history biology. Such knowledge is accumulating for holometabolous insects, whose growth is characterised and body size affected by moulting. According to the oxygen-dependent induction of moulting (ODIM) hypothesis, moult is induced at a critical mass at which oxygen demand of growing tissues overrides the supply from the tracheal respiratory system, which principally grows only at moults. Support for the ODIM hypothesis is controversial, partly because of a lack of proper data to explicitly test the hypothesis. The ODIM hypothesis predicts that the critical mass is positively correlated with oxygen partial pressure (P-O2) and negatively with temperature. To resolve the controversy that surrounds the ODIM hypothesis, we rigorously test these predictions by exposing penultimate-instar Orthosia gothica (Lepidoptera: Noctuidae) larvae to temperature and moderate P-O2 manipulations in a factorial experiment. The relative mass increment in the focal instar increased along with increasing P-O2, as predicted, but there was only weak suggestive evidence of the temperature effect. Probably owing to a high measurement error in the trait, the effect of P-O2 on the critical mass was sex specific; high P-O2 had a positive effect only in females, whereas low P-O2 had a negative effect only in males. Critical mass was independent of temperature. Support for the ODIM hypothesis is partial because of only suggestive evidence of a temperature effect on moulting, but the role of oxygen in moult induction seems unambiguous. The ODIM mechanism thus seems worth considering in body size analyses.

  • 25.
    Kivelä, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Adaptive developmental plasticity in a butterfly: mechanisms for size and time at pupation differ between diapause and direct development2017In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 122, no 1, p. 46-57Article in journal (Refereed)
    Abstract [en]

    Diapause (overwintering) and direct development are alternative developmental pathways in temperate insects. Diapause necessitates physiological preparations for dormancy, while direct development is associated with strong time constraints, resulting in selection for fast development under the direct development pathway. Physiological and behavioural preparations for pupation contribute to development time, so divergent selection in them is expected between the alternative developmental pathways. Critical mass for pupation induction is a central physiological parameter for the pupation process. Here, we compare the critical masses and the characteristics of the wandering stage - wandering taking place after the cessation of growth and before pupation - between diapausing and directly developing larvae in the butterfly Pieris napi. Critical mass estimation succeeded only for diapausing individuals, among which it was lower in females than in males, indicating an inter-pathway difference in the physiology of critical mass. Directly developing individuals wandered for a shorter time and distance and lost less mass before pupation than diapausing individuals. These physiological and behavioural differences represent adaptive phenotypic plasticity and contribute to fast development under direct development. Thus, the observed developmental plasticity in physiology offers a mechanistic explanation for adaptive life-history variation between alternative developmental pathways and sexual dimorphism.

  • 26.
    Kivelä, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Friberg, Magne
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Leimar, Olof
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Towards a mechanistic understanding of insect life history evolution: oxygen-dependent induction of moulting explains moulting sizes2016In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 117, no 3, p. 586-600Article in journal (Refereed)
    Abstract [en]

    Moults characterise insect growth trajectories, typically following a consistent pattern known as Dyar's rule; proportional size increments remain constant across inter-instar moults. Empirical work suggests that oxygen limitation triggers moulting. The insect respiratory system, and its oxygen supply capacity, grows primarily at moults. It is hypothesized that the oxygen demand increases with increasing body mass, eventually meeting the oxygen supply capacity at an instar-specific critical mass where moulting is triggered. Deriving from this hypothesis, we develop a novel mathematical model for moulting and growth in insect larvae. Our mechanistic model has great success in predicting moulting sizes in four butterfly species, indirectly supporting a size-dependent mechanism underlying moulting. The results demonstrate that an oxygen-dependent induction of moulting mechanism would be sufficient to explain moulting sizes in the study species. Model predictions deviated slightly from Dyar's rule, the deviations being typically negligible within the present data range. The developmental decisions (e.g. moulting) made by growing larvae significantly affect age and size at maturity, which has important life history implications. The successful modelling of moulting presented here provides a novel framework for the development of realistic insect growth models, which are required for a better understanding of life history evolution.

  • 27. Kivelä, Sami M.
    et al.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Lehmann, Philipp
    Stockholm University, Faculty of Science, Department of Zoology.
    Developmental plasticity in metabolism but not in energy reserve accumulation in a seasonally polyphenic butterfly2019In: Journal of Experimental Biology, ISSN 0022-0949, E-ISSN 1477-9145, Vol. 222, no 13, article id jeb202150Article in journal (Refereed)
    Abstract [en]

    The evolution of seasonal polyphenisms (discrete phenotypes in different annual generations) associated with alternative developmental pathways of diapause (overwintering) and direct development is favoured in temperate insects. Seasonal life history polyphenisms are common and include faster growth and development under direct development than in diapause. However, the physiological underpinnings of this difference remain poorly known despite its significance for understanding the evolution of polyphenisms. We measured respiration and metabolic rates through the penultimate and final larval instars in the butterfly Pieris napi and show that directly developing larvae grew and developed faster and had a higher metabolic rate than larvae entering pupal diapause. The metabolic divergence appeared only in the final instar, that is, after induction of the developmental pathway that takes place in the penultimate instar in P. napi. The accumulation of fat reserves during the final larval instar was similar under diapause and direct development, which was unexpected as diapause is predicted to select for exaggerated reserve accumulation. This suggests that overwinter survival in diapause does not require larger energy reserves than direct development, likely because of metabolic suppression in diapause pupae. The results, nevertheless, demonstrate that physiological changes coincide with the divergence of life histories between the alternative developmental pathways, thus elucidating the proximate basis of seasonal life history polyphenisms.

  • 28.
    Kivelä, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Oulu, Finland.
    Svensson, Beatrice
    Stockholm University, Faculty of Science, Department of Zoology.
    Tiwe, Alma
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Thermal plasticity of growth and development varies adaptively among alternative developmental pathways2015In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 69, no 9, p. 2399-2413Article in journal (Refereed)
    Abstract [en]

    Polyphenism, the expression of discrete alternative phenotypes, is often a consequence of a developmental switch. Physiological changes induced by a developmental switch potentially affect reaction norms, but the evolution and existence of alternative reaction norms remains poorly understood. Here, we demonstrate that, in the butterfly Pieris napi (Lepidoptera: Pieridae), thermal reaction norms of several life history traits vary adaptively among switch-induced alternative developmental pathways of diapause and direct development. The switch was affected both by photoperiod and temperature, ambient temperature during late development having the potential to override earlier photoperiodic cues. Directly developing larvae had higher development and growth rates than diapausing ones across the studied thermal gradient. Reaction norm shapes also differed between the alternative developmental pathways, indicating pathway-specific selection on thermal sensitivity. Relative mass increments decreased linearly with increasing temperature and were higher under direct development than diapause. Contrary to predictions, population phenology did not explain trait variation or thermal sensitivity, but our experimental design probably lacks power for finding subtle phenology effects. We demonstrate adaptive differentiation in thermal reaction norms among alternative phenotypes, and suggest that the consequences of an environmentally dependent developmental switch primarily drive the evolution of alternative thermal reaction norms in P. napi.

  • 29.
    Kivelä, Sami M.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology. University of Oulu, Finland.
    Välimäki, Panu
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Evolution of alternative insect life histories in stochastic seasonal environments2016In: Ecology and Evolution, ISSN 2045-7758, E-ISSN 2045-7758, Vol. 6, no 16, p. 5596-5613Article in journal (Refereed)
    Abstract [en]

    Deterministic seasonality can explain the evolution of alternative life history phenotypes (i.e., life history polyphenism) expressed in different generations emerging within the same year. However, the influence of stochastic variation on the expression of such life history polyphenisms in seasonal environments is insufficiently understood. Here, we use insects as a model and explore (1) the effects of stochastic variation in seasonality and (2) the life cycle on the degree of life history differentiation among the alternative developmental pathways of direct development and diapause (overwintering), and (3) the evolution of phenology. With numerical simulation, we determine the values of development (growth) time, growth rate, body size, reproductive effort, adult life span, and fecundity in both the overwintering and directly developing generations that maximize geometric mean fitness. The results suggest that natural selection favors the expression of alternative life histories in the alternative developmental pathways even when there is stochastic variation in seasonality, but that trait differentiation is affected by the developmental stage that overwinters. Increasing environmental unpredictability induced a switch to a bet-hedging type of life history strategy, which is consistent with general life history theory. Bet-hedging appeared in our study system as reduced expression of the direct development phenotype, with associated changes in life history phenotypes, because the fitness value of direct development is highly variable in uncertain environments. Our main result is that seasonality itself is a key factor promoting the evolution of seasonally polyphenic life histories but that environmental stochasticity may modulate the expression of life history phenotypes.

  • 30.
    Kodandaramaiah, Ullasa
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Konvicka, Martin
    Tammaru, Toomas
    Wahlberg, Niklas
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Physics.
    Phylogeography of the threatened butterfly, the woodland brown Lopinga achine (Nymphalidae Satyrinae):  implications for conservation2012In: Journal of Insect Conservation, ISSN 1366-638X, E-ISSN 1572-9753, Vol. 16, no 2, p. 305-313Article in journal (Refereed)
    Abstract [en]

    We have studied the phylogeography of the red-listed Palearctic butterfly Lopinga achine (Nymphalidae: Satyrinae) based on 1,450 base pairs of mitochondrial DNA sequences from 86 individuals representing 12 populations. Our results indicate a strong structuring of genetic variation, with among-population differences accounting for ca. 67% of the variation and almost all populations being significantly differentiated from each other. We surmise that the insular nature of populations as well as the low dispersal ability of the species has given rise to such a pattern. The genetic diversity within populations is low compared to that in other butterflies. Our results point to a scenario where the species originated in the Eastern Palearctic and expanded into Europe. Based on the analyses, we suggest that the Czech population merits the highest conservation priority. The two Swedish populations represent a distinct evolutionary lineage, and hence merit high conservation attention. The Estonian and Asian populations had the highest genetic diversity, and although we do not consider them to be under immediate threat, their genetic diversity should be conserved in the long term.

  • 31.
    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.

  • 32.
    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.

  • 33.
    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.

  • 34.
    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.

  • 35.
    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.

  • 36. Lindman, Ly
    et al.
    Johansson, Britta
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Tammaru, Toomas
    Host plant relationships of an endangered butterfly, Lopinga achine (Lepidoptera: Nymphalidae) in northern Europe2013In: Journal of Insect Conservation, ISSN 1366-638X, E-ISSN 1572-9753, Vol. 17, no 2, p. 375-383Article in journal (Refereed)
    Abstract [en]

    The aim of the present study was to evaluate-in a geographic perspective-the role of host plant as a determinant of habitat quality for Lopinga achine, a satyrine butterfly endangered over much of its European range. Laboratory trials were performed to record host choices made by the ovipositing females as well as by neonate larvae. In rearing experiments, growth performance and mortality on different host plants was determined. Oviposition was found to be indiscriminate but larvae were shown to be able to choose between host plants, with the choices made broadly consistent with growth performance of the larvae on particular hosts. Nevertheless, most grasses and sedges offered were found to support larval development reasonably well. No clear superiority of the previously suggested primary host plant Carex montana could be shown. Importantly, no differences in host plant relationships were found between the populations of Sweden, western Estonia and eastern Estonia. In particular, the larvae originating from eastern Estonian populations developed on C. montana equally well even if the plant is absent from their native habitat. In the context of species conservation, one should conclude that L. achine is polyphagous enough on various grasses and sedges so that the presence of any particular host species cannot be a critical component of habitat quality. Nevertheless, some preference to broad- and soft-leaved hosts, as well as sensitivity to host wilting, may partly explain the butterfly's preference to moist forest habitats, further emphasizing the central role of habitat management in the conservation practice of this species. In turn, the absence of ecological differences between geographic populations should enable conservationists to successful transfer their experience across national boundaries.

  • 37.
    Löwenborg, Kristin
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Hagman, Mattias
    Stockholm University, Faculty of Science, Department of Zoology.
    How a thermal dichotomy in nesting environments influences offspring of the world's most northerly oviparous snake, Natrix natrix (Colubridae)2012In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 107, no 4, p. 833-844Article in journal (Refereed)
    Abstract [en]

    Temperature has a major influence on the rate of embryonic development in ectothermic organisms. While incubation experiments unambiguously show that constant high temperature accelerates development and shortens embryonic life, studies on the effect of fluctuating temperatures have generated contradictory results. Grass snakes (Natrix natrix) occur at latitudes and altitudes that are unusually cool for an oviparous reptile. In these cool climates females typically lay their eggs in heat-generating anthropogenic microhabitats that provide either a highly fluctuating (compost piles) or a relatively constant (manure heaps) thermal nesting environment. A laboratory experiment with fluctuating and constant incubation temperatures mimicking those recorded in such nests in the field showed that this nest-site dichotomy influences the development of the embryos, and the morphology and locomotor performance of the hatchlings. The incubation period increased at fluctuating temperatures and the fact that the rate of embryonic development showed a decelerating pattern with temperature suggests that periods of low temperature had a relatively larger influence on average development than periods of high temperature. Our study demonstrates how a dichotomy in the nesting environments available to female grass snakes in cool climates can affect variation in the duration of the incubation period and offspring phenotypes in ways that may have consequences for fitness.

  • 38. 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.

  • 39.
    Navarro-Cano, Jose A.
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Karlsson, Bengt
    Stockholm University, Faculty of Science, Department of Zoology.
    Posledovich, Diana
    Stockholm University, Faculty of Science, Department of Zoology.
    Toftegaard, Tenna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Climate change, phenology, and butterfly host plant utilization2015In: Ambio, ISSN 0044-7447, E-ISSN 1654-7209, Vol. 44, no S!, p. S78-S88Article in journal (Refereed)
    Abstract [en]

    Knowledge of how species interactions are influenced by climate warming is paramount to understand current biodiversity changes. We review phenological changes of Swedish butterflies during the latest decades and explore potential climate effects on butterfly-host plant interactions using the Orange tip butterfly Anthocharis cardamines and its host plants as a model system. This butterfly has advanced its appearance dates substantially, and its mean flight date shows a positive correlation with latitude. We show that there is a large latitudinal variation in host use and that butterfly populations select plant individuals based on their flowering phenology. We conclude that A. cardamines is a phenological specialist but a host species generalist. This implies that thermal plasticity for spring development influences host utilization of the butterfly through effects on the phenological matching with its host plants. However, the host utilization strategy of A. cardamines appears to render it resilient to relatively large variation in climate.

  • 40.
    Neethiraj, Ramprasad
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Pruisscher, Peter
    Stockholm University, Faculty of Science, Department of Zoology.
    Pruisscher Keehnen, Naomi
    Stockholm University, Faculty of Science, Department of Zoology.
    Woronik, Alyssa
    Gotthard, Karl
    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.
    A dark melanic morph of Pieris napi shares its origins with other dark morphs of LepidopteraManuscript (preprint) (Other academic)
  • 41.
    Posledovich, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Toftegaard, Tenna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Navarro-Cano, Jose A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Latitudinal variation in thermal reaction norms of post-winter pupal development in two butterflies differing in phenological specialization2014In: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 113, no 4, p. 981-991Article in journal (Refereed)
    Abstract [en]

    Latitudinal clines in thermal reaction norms of development are a common phenomenon in temperate insects. Populations from higher latitudes often develop faster throughout the range of relevant temperatures (i.e countergradient variation) because they must be able to complete their life cycle within a shorter seasonal time window compared to populations at lower latitudes. In the present study, we experimentally demonstrate that two species of butterflies Anthocharis cardamines (L.) and Pieris napi (L.) instead show a cogradient variation in thermal reaction norms of post-winter pupal development so that lower latitude populations develop faster than higher latitude populations. The two species share host plants but differ in the degree of phenological specialization, as well as in the patterns of voltinism. We suggest that the pattern in A. cardamines, a univoltine phenological specialist feeding exclusively on flowers and seedpods, is the result of selection for matching to the phenological pattern of its local host plants. The other species, P. napi, is a phenological generalist feeding on the leaves of the hosts and it shows a latitudinal cline in voltinism. Because the latitudinal pattern in P. napi was an effect of slow development in a fraction of the pupae from the most northern population, we hypothesize that this population may include both bivoltine and univoltine genotypes. Consequently, although the two species both showed cogradient patterns in thermal reaction norms, it appears likely that this was for different reasons.

  • 42.
    Posledovich, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Toftegaard, Tenna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Latitudinal variation in diapause duration and post-winter development in two pierid butterflies in relation to phenological specialization2015In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 177, no 1, p. 181-190Article in journal (Refereed)
    Abstract [en]

    Diapause plays a central role in insect life cycles by allowing survival during adverse seasonal conditions as well as synchronizing life cycles with the period of mate and food availability. Seasonal timing is expected to be particularly important for species that are dependent on resources available during a short time window-so-called phenological specialists-and latitudinal clines in seasonality are expected to favor local adaptation in phenological timing. However, to what degree latitudinal variation in diapause dynamics and post-winter development due to such local adaptation is influenced by the degree of phenological specialization is not well known. We experimentally studied two pierid butterfly species and found that the phenological specialist Anthocharis cardamines had shorter diapause duration than the phenological generalist Pieris napi along a latitudinal gradient in Sweden. Moreover, diapause duration increased with latitude in P. napi but not in A. cardamines. Sensitivity of the two species to winter thermal conditions also differed; additional cold temperature during the winter period shortened diapause duration for P. napi pupae but not for A. cardamines pupae. In both species, post-winter pupal development was faster after longer periods of cold conditions, and more southern populations developed faster than northern populations. Post-winter development was also invariably faster at higher temperatures in both species. We argue that the observed differences in diapause dynamics between the two species might be explained by the difference in phenological specialization that influences the costs of breaking diapause too early in the season.

  • 43.
    Posledovich, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Toftegaard, Tenna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Phenological synchrony between a butterfly and its host plants: Experimental test of effects of spring temperature2018In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 87, no 1, p. 150-161Article in journal (Refereed)
    Abstract [en]

    1. Climate-driven changes in the relative phenologies of interacting species may potentially alter the outcome of species interactions. 2. Phenotypic plasticity is expected to be important for short-term response to new climate conditions, and differences between species in plasticity are likely to influence their temporal overlap and interaction patterns. As reaction norms of interacting species may be locally adapted, any such climate-induced change in interaction patterns may vary among localities. However, consequences of spatial variation in plastic responses for species interactions are understudied. 3. We experimentally explored how temperature affected synchrony between spring emergence of a butterfly, Anthocharis cardamines, and onset of flowering of five of its host plant species across a latitudinal gradient. We also studied potential effects on synchrony if climate-driven northward expansions would be faster in the butterflies than in host plants. Lastly, to assess how changes in synchrony influence host use we carried out an experiment to examine the importance of the developmental stage of plant reproductive structures for butterfly oviposition preference. 4. In southern locations, the butterflies were well-synchronized with the majority of their local host plant species across temperatures, suggesting that thermal plasticity in butterfly development matches oviposition to host plant development and that thermal reaction norms of insects and plants result in similar advancement of spring phenology in response to warming. In the most northern region, however, relative phenology between the butterfly and two of its host plant species changed with increased temperature. We also show that the developmental stage of plants was important for egg-laying, and conclude that temperature-induced changes in synchrony in the northernmost region are likely to lead to shifts in host use in A.cardamines if spring temperatures become warmer. Northern expansion of butterfly populations might possibly have a positive effect on keeping up with host plant phenology with more northern host plant populations. 5. Considering that the majority of insect herbivores exploit multiple plant species differing in their phenological response to spring temperatures, temperature-induced changes in synchrony might lead to shifts in host use and changes in species interactions in many temperate communities.

  • 44.
    Posledovich, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Toftegaard, Tenna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    The developmental race between maturing host plants and their butterfly herbivore – the influence of phenological matching and temperature2015In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 84, no 6, p. 1690-1699Article in journal (Refereed)
    Abstract [en]

    Interactions between herbivorous insects and their host plants that are limited in time are widespread. Therefore, many insect-plant interactions result in a developmental race, where herbivores need to complete their development before plants become unsuitable, while plants strive to minimize damage from herbivores by outgrowing them. When spring phenologies of interacting species change asymmetrically in response to climate warming, there will be a change in the developmental state of host plants at the time of insect herbivore emergence. In combination with altered temperatures during the subsequent developmental period, this is likely to affect interaction strength as well as fitness of interacting species. Here, we experimentally explore whether the combined effect of phenological matching and thermal conditions influence the outcome of an insect-host interaction. We manipulated both developmental stages of the host plants at the start of the interaction and temperature during the subsequent developmental period in a model system of a herbivorous butterfly, Anthocharis cardamines, and five of its Brassicaceae host plant species. Larval performance characteristics were favoured by earlier stages of host plants at oviposition as well as by higher developmental temperatures on most of the host species. The probability of a larva needing a second host plant covered the full range from no influence of either phenological matching or temperature to strong effects of both factors, and complex interactions between them. The probability of a plant outgrowing a larva was dependent only on the species identity. This study demonstrates that climatic variation can influence the outcome of consumer-resource interactions in multiple ways and that its effects differ among host plant species. Therefore, climate warming is likely to change the temporal match between larval and plant development in some plant species, but not in the others. This is likely to have important implications for host plant use and possibly influence competitive relationships.

  • 45.
    Posledovich, Diana
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Toftegaard, Tenna
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Wiklund, Christer
    Stockholm University, Faculty of Science, Department of Zoology.
    Ehrlén, Johan
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Weak effect of spring temperatures on phenological synchrony between herbivore emergence and host plant suitabilityManuscript (preprint) (Other academic)
    Abstract [en]

    Many species interactions are maintained by precise timing of life-cycle events across seasonal variation. Ecological implications of changes in phenologies, associated with climate change, with respect to species interactions are to a large extent unexplored. Changes in phenological distance between herbivores and their host plant species under new environmental conditions may potentially lead to shifts in host use patterns, with some plant species becoming more or less available at the time of a herbivore’s emergence. In addition, latitudinal variation in the timing of phenological events can lead to different patterns in host use shifts among populations of a given herbivore. Here we explored latitudinal variation in the effects of temperature on the degree of phenological synchrony between emergence of a butterfly, A. cardamines, and five of its herbaceous host plant species in a set of laboratory experiments to investigate the possibility that there will be shifts in the butterfly’ host utilization due to changes in thermal environment. The results suggest a similar temperature-mediated phenological plasticity between the butterflies and their host plants in three latitudinally divergent populations. In general, butterflies appeared to be well-synchronized with the majority of their host plant species across temperatures. In the most northern region, however, phenological distance between the butterfly and two out of four plant species was affected by temperature and decreased in warmer treatments. We relate this to a lower diversity of plant species and shorter period of host availability in the northern region. This creates a stronger selection pressure on the northern butterflies for a closer matching of their emergence to the plant flowering period. As the butterflies discriminated against non-flowering hosts with respect to oviposition, we conclude that a shift in host use in A. cardamines appears to be a possible scenario under spring warming, especially in the northern region.

  • 46.
    Pruisscher, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Larsdotter-Mellström, Helena
    Stockholm University, Faculty of Science, Department of Zoology. The University of Western Australia, Australia.
    Stefanescu, Constantí
    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.
    Sex-linked inheritance of diapause induction in the butterfly Pieris napi2017In: Physiological entomology (Print), ISSN 0307-6962, E-ISSN 1365-3032, Vol. 42, no 3, p. 257-265Article in journal (Refereed)
    Abstract [en]

    Many temperate insects survive harsh environmental conditions, such as winter, by entering a state of developmental arrest. This diapause state is predominantly induced by photoperiod. The photoperiod varies with latitude and has led to local adaptation in the photoperiodic induction of diapause in many insects. To understand the rapid evolution of the photoperiodic threshold, it is important to investigate and understand the underlying genetic mechanisms. In the present study, the genetic basis of photoperiodic diapause induction is investigated in the green-veined white butterfly Pieris napi (Lepidoptera, Pieridae) by assaying diapause induction in a range of conditions for a Swedish and Spanish population. Furthermore, the inheritance of diapause induction is assessed in reciprocal F1 hybrids and backcrosses between the two populations. The southern population shows a clear photoperiodic threshold determining diapause or direct development, whereas the northern populations show a high incidence of diapause, regardless of photoperiod. The hybrid crosses reveal that the inheritance of diapause induction is strongly sex-linked, and that diapause incidence in the genetic crosses is highly dependent on photoperiod. This emphasizes the importance of assaying a range of conditions in diapause inheritance studies. The results indicate a strongly heritable diapause induction with a major component on the Z-chromosome, as well as a minor effect of the autosomal background.

  • 47.
    Pruisscher, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Lehmann, Philipp
    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.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Wheat, Christopher
    Stockholm University, Faculty of Science, Department of Zoology.
    Transcriptomic profiling of pupal diapause in the butterfly Pieris napiManuscript (preprint) (Other academic)
    Abstract [en]

    Diapause is a common means of overwintering among insects that is characterized by arrested development and increased tolerance to stress and cold. Diapause is a vital aspect of life cycle timing, and while the expression of specific candidate genes during diapause have been investigated, there is no general understanding of the dynamics of the transcriptional landscape as a whole during the extended diapause phenotype. Here we performed a time-course experiment using RNA-Seq on the head and abdomen in the butterfly Pieris napi. In both body parts, comparing diapause and directly developing siblings, differentially expressed genes are detected from the first day of pupal development and onwards, varying dramatically across these formative stages. During diapause there are strong gene expression dynamics independent of environmental conditions, revealing a pre-programmed transcriptional landscape that is active during the winter. Different biological processes appear to be active in the two body parts. Still, adults emerging from either the direct or diapause pathways do not show large transcriptomic differences, suggesting the adult phenotype is strongly canalized.

  • 48.
    Pruisscher, Peter
    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.
    Wheat, Christopher W.
    Stockholm University, Faculty of Science, Department of Zoology.
    Genetic variation underlying local adaptation of diapause induction along a cline in a butterfly2018In: Molecular Ecology, ISSN 0962-1083, E-ISSN 1365-294X, Vol. 27, no 18, p. 3613-3626Article in journal (Refereed)
    Abstract [en]

    Diapause is a life history strategy allowing individuals to arrest development until favourable conditions return, and it is commonly induced by shortened day length that is latitude specific for local populations. Although understanding the evolutionary dynamics of a threshold trait like diapause induction provides insights into the adaptive process and adaptive potential of populations, the genetic mechanism of variation in photoperiodic induction of diapause is not well understood. Here, we investigate genetic variation underlying latitudinal variation in diapause induction and the selection dynamics acting upon it. Using a genomewide scan for divergent regions between two populations of the butterfly Pararge aegeria that differ strongly in their induction thresholds, we identified and investigated the patterns of variation in those regions. We then tested the association of these regions with diapause induction using between-population crosses, finding significant SNP associations in four genes present in two chromosomal regions, one with the gene period, and the other with the genes kinesin, carnitine O-acetyltransferase and timeless. Patterns of allele frequencies in these two regions in population samples along a latitudinal cline suggest strong selection against heterozygotes at two genes within these loci (period, timeless). Evidence for additional loci modifying the diapause decision was found in patterns of allelic change in relation to induction thresholds over the cline, as well as in backcross analyses. Taken together, population-specific adaptations of diapause induction appear to be due to a combination of alleles of larger and smaller effect size, consistent with an exponential distribution of effect sizes involved in local adaption.

  • 49.
    Pruisscher, Peter
    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.
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    A chromosomal block containing clock genes associates with variation in diapause inductionManuscript (preprint) (Other academic)
    Abstract [en]

    Developmental plasticity describes the capacity of individuals with the same genotype to induce permanent change in a phenotype depending on a specific external input. One well-studied example of adaptive developmental plasticity is the induction of facultative diapause in insects. Studies investigating the inheritance of diapause induction have suggested diverse genetic backgrounds. However, only few studies have performed unbiased genome scans to identify genes affecting the induction decision. Here we perform an unbiased whole genome scan to identify divergence between two populations that differ in their propensity to diapause, finding low divergence between these populations. We then investigate genetic differences between diapausing and directly developing siblings from backcrosses of these populations that revealed one particular region of divergence. This region is located on the Z-chromosome and contained three circadian clock genes, cyc_2, clock, and per. The results from this study help understand the genetic basis that is underlying plasticity.

  • 50.
    Rowiński, Piotr
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Laurila, Anssi
    Gotthard, Karl
    Stockholm University, Faculty of Science, Department of Zoology.
    Sowersby, Will
    Stockholm University, Faculty of Science, Department of Zoology.
    Lind, Martin
    Richter-Boix, Alex
    Eckerström-Liedholm, Simon
    Stockholm University, Faculty of Science, Department of Zoology.
    Rogell, Björn
    Stockholm University, Faculty of Science, Department of Zoology.
    Thermally induced parental effects influence life history traits and covary with an environmental cline in common frog populationsManuscript (preprint) (Other academic)
    Abstract [en]

    Across latitudinal clines, the juvenile developmental rates of ectotherms often covary with the length of the growing season, due to life-history trade-offs imposed by time-constrained environments. However, as the start of the growing season often varies substantially across years, adaptive parental effects on juvenile developmental rates may mediate the costs of a delayed spring. By employing a meta-analysis, we tested whether larval developmental rates across a latitudinal cline of common frogs (Rana temporaria) are affected by fluctuating onsets of breeding, across years. We predicted that larval developmental rate will be inversely related to the onset of breeding, and that northern populations will be more prone to shorten their developmental rate in response to late breeding, as the costs of delayed metamorphosis should be highest in areas with a shorter growing season. We found that the larval period of both northern and southern populations responded to parental environmental conditions to similar degree in absolute terms, but in different directions. In northern populations, a late season start correlated with decreased development time, suggesting that the evolution of parental effects aid population persistence in time-constrained environments. In southern populations, late season start correlated with increased development time, which could potentially be explained as a predator avoidance strategy. Our findings suggest that local ecological variables can induce adaptive parental effects, but responses are complex, and likely trade-off with other ecological factors.

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