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  • 1. Andersson, J.
    et al.
    Borg-Karlson, A-K
    Vongvanich, N.
    Wiklund, C.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Male sex pheromone release and female mate choice in a butterfly.2007Ingår i: The Journal of Experimental Biology, Vol. 210, s. 964-970Artikel i tidskrift (Refereegranskat)
  • 2.
    Arvanitis, Leena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Ekologi.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Butterfly seed predation: effects of landscape characteristics, plant ploidy level and population structure2007Ingår i: Oecologia, ISSN 0029-8549, Vol. 152, nr 2, s. 275-285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyploidization has been suggested as one of the most common mechanisms for plant diversification. It is often associated with changes in several morphological, phenological and ecological plant traits, and therefore has the potential to alter insect–plant interactions. Nevertheless, studies evaluating the effect of plant polyploidy on interspecific interactions are still few. We investigated pre-dispersal seed predation by the butterfly Anthocharis cardamines in 195 populations of two ploidy levels of the herb Cardamine pratensis (tetraploid ssp. pratensis, 2n = 30 vs. octoploid ssp. paludosa, 2n = 56–64). We asked if differences in incidence and intensity of predation among populations were related to landscape characteristics, plant ploidy level and population structure. The incidence of the seed predator increased with increasing plant population size and decreasing distance to nearest population occupied by A. cardamines. The intensity of predation decreased with increasing plant population size and was not affected by isolation. Probability of attack decreased with increasing shading, and intensity of predation was higher in grazed than in non-grazed habitats. The attack intensity increased with increasing mean flower number of plant population, but was not affected by flowering phenology. Individuals in tetraploid populations suffered on average from higher levels of seed predation, had higher mean flower number, were less shaded and occurred more often in grazed habitats than octoploid populations. When accounting for differences in habitat preferences between ploidy levels there was no longer a difference in intensity of predation, suggesting that the observed differences in attack rates among populations of the two ploidy levels are mediated by the habitat. Overall, our results suggest that polyploidization is associated with differentiation in habitat preferences and phenotypic traits leading to differences in interspecific interaction among plant populations. This, in turn, may facilitate further divergence of ploidy levels.

  • 3.
    Arvanitis, Leena
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Wiklund, Christer
    Zoologiska institutionen. Ekologi.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Botaniska institutionen. Växtekologi.
    Plant ploidy level influences selection by butterfly seed predators2008Ingår i: Oikos, Vol. 117, s. 1020-1025Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyploidization is a common route to plant diversification. Polyploids often differ from their progenitors in size, flower number, flower size and flowering phenology. Such differences may translate into differences in the intensity of interactions with animals. Here we investigated the impact of the ploidy-related differences in tetraploids and octoploids of the perennial herb Cardamine pratensis on pre-dispersal seed predation by the butterfly Anthocharis cardamines. The probability of escaping attack was lower for octoploids than for tetraploids, even after accounting for the fact that octoploids were larger and had fewer flowers than tetraploids. Flower shoot size was correlated with probability of attack in tetraploids but not in octoploids. Differences in plant traits associated with polyploidization can alter interactions with animals, and animal-mediated differences in trait selection between ploidy types can contribute to their further divergence.

  • 4. Arvanitis, Leena
    et al.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Münzbergova, Zuzana
    Dahlgren, Johan P
    Ehrlén, Johan
    Novel antagonistic interactions associated with plant polyploidization influence trait selection and habitat preference.2010Ingår i: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 13, nr 3, s. 330-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Polyploidization is an important mechanism for sympatric speciation in plants. Still, we know little about whether plant polyploidization leads to insect host shifts, and if novel interactions influence habitat and trait selection in plants. We investigated herbivory by the flower bud gall-forming midge Dasineura cardaminis on tetraploids and octoploids of the herb Cardamine pratensis. Gall midges attacked only octoploid plant populations, and a transplantation experiment confirmed this preference. Attack rates were higher in populations that were shaded, highly connected or occurred along stream margins. Within populations, late-flowering individuals with many flowers were most attacked. Galling reduced seed production and significantly influenced phenotypic selection on flower number. Our results suggest that an increase in ploidy may lead to insect host shifts and that plant ploidy explains insect host use. In newly formed plant polyploids, novel interactions may alter habitat preferences and trait selection, and influence the further evolution of cytotypes.

  • 5.
    Berger, D.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Friberg, M.
    Olofsson, M.
    Wiklund, C.
    Large females lose more: sexual conflicts reduce female fecundity and directional selection on body size in the butterfly Leptidea sinapis.Manuskript (Övrig (populärvetenskap, debatt, mm))
  • 6.
    Berger, David
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Uppsala University, Sweden.
    Olofsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Friberg, Magne
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. University of California Santa Cruz, USA.
    Karlsson, Bengt
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Intraspecific variation in body size and the rate of reproduction in female insects- adaptive allometry or biophysical constraint?2012Ingår i: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 81, nr 6, s. 1244-1258Artikel i tidskrift (Refereegranskat)
    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.

  • 7.
    Berger, David
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Olofsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Friberg, Magne
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Ecological Constraints on Female Fitness in a Phytophagous Insect2012Ingår i: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 180, nr 4, s. 464-480Artikel i tidskrift (Refereegranskat)
    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.

  • 8.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Berger, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Olofsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Kemp, Darrell
    James Cook University, Australia.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Mating success of resident versus non-resident males in a territorial butterfly2007Ingår i: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 274, nr 1618, s. 1659-1665Artikel i tidskrift (Refereegranskat)
    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.

  • 9.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Mate acquisition by females in a butterfly: the effects of mating status and age on female mate-locating behaviour2011Ingår i: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 81, nr 1, s. 225-229Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Olofsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Contest outcome in a territorial butterfly: the role of motivation2010Ingår i: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 277, nr 1696, s. 3027-3033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In many butterfly species, males compete over areas advantageous for encountering females. Rules for contest settlement are, however, largely unknown and neither morphological nor physiological traits can reliably predict the contest outcome. Here, we test the hypothesis that contests are settled in accordance with a motivation asymmetry. We staged contests between males of Pararge aegeria and after removing the resident, the non-resident was allowed (i) either to interact with a non-receptive female for 30 min (n = 30) or (ii) to spend 30 min alone in the cage (n = 30), after which the initial resident was reintroduced. The results show that males that had interacted with a female had a higher probability of becoming dominant and reversing contest outcome. Moreover, males that were faster to take over a vacant territory when the resident was removed were more likely to become dominant. Here, we show for the first time, to our knowledge, that frequent encounters with a mated female can increase male motivation to persist in a territorial contest in a butterfly. Further, we suggest that variation in intrinsic motivation reflects male eagerness to take over vacant territory. This study indicates that variation in resource value and motivational asymmetries are important for settling contests in butterflies.

  • 11.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Differences in mate location behaviours between residents and nonresidents in a territorial butterfly2009Ingår i: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, ISSN 0003-3472, Vol. 78, nr 5, s. 1161-1167Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mate location strategies vary between species. Among butterflies two strategies are recognized: 'patrolling' males spend their life on the wing searching for females and 'perching' males stay at a specific site waiting to intercept passing females. In the speckled wood butterfly, Pararge aegeria, two alternative male strategies have been described: dominant males adopt a perching strategy monopolizing large sunspots on the forest floor, and subdominant males adopt a patrolling strategy. However, comparative analyses have shown that body design differs between perching and patrolling species, hence constraining opportunity for within-species variation in mate location strategy. We tested whether males differ in their propensity to adopt perching or patrolling behaviour by recording time spent flying during 30 min when alone in a large cage with only one large sunspot and many smaller ones, and whether subdominant males adopt a patrolling strategy by allowing dyads of males to interact in the cage for 60 min and recording the same behaviours again. All males adopted perching behaviour when alone, and subdominant males in dyads spent only a short time in extended flights after losing contests over territory ownership, soon returning to a perching strategy and making the best of a bad job from the vantage point of a small sunspot. We argue that previous descriptions of subdominant male P. aegeria adopting a patrolling strategy are based on too short observation periods, and have mistaken males in temporary transit for males adopting patrolling behaviour.

  • 12.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för zoologisk ekologi.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för zoologisk ekologi.
    Erratum to: Differences in mate location behaviours between residents and nonresidents in a territorial butterfly2010Ingår i: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 80, s. 593-Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 13.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för zoologisk ekologi.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för zoologisk ekologi.
    Territorialitet hos dagfjärilar2011Ingår i: Fauna & Flora, Vol. 106, nr 1, s. 20-25Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 14.
    Bergman, Martin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Visual mate detection and mate flight pursuit in relation to sunspot size in a woodland territorial butterfly2009Ingår i: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, ISSN 0003-3472, Vol. 78, nr 1, s. 17-23Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Territory residency is associated with considerable benefits. In the speckled wood butterfly, Pararge aegeria, males fight over ownership of large sunspots in open forest habitats; winners become sunspot residents, and losers become nonterritorial and sit and wait for females in small sunspots. A previous study has shown that residents have higher mating success than nonterritorial males, although females are not more attracted to territorial males or sunspot territories per se. Here we tested the hypotheses (1) that the higher success of resident males is caused by visual mate detection being more efficient in a large than in a small sunspot, and (2) that only sunspots above a certain size are defended as territories. Field assessment of territorial sunspot size showed that defended sunspots were significantly larger than 'average sunspots' on the forest floor. Experimental tests of male ability to detect visually a model butterfly passing through a sunspot showed that males were more successful in pursuing and intercepting a passing model when. own a longer distance in the sunspot. Hence, we conclude that light conditions and associated visual mate detection and ability to complete mate flight pursuit can explain why P. aegeria males defend territories in large sunspots in forest habitats.

  • 15.
    Bergström, Jonas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Effects of size and nuptial gifts on butterfly reproduction: can females compensate for a smaller size through male-derived nutrients?2002Ingår i: Behavioral Ecology and Sociobiology, Vol. 52, s. 296-302Artikel i tidskrift (Refereegranskat)
  • 16.
    Bergström, Jonas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Male versus female influence over mating rate in the butterfly Pieris napi.Ingår i: Behavioral Ecology and SociobiologyArtikel i tidskrift (Refereegranskat)
  • 17.
    Bergström, Jonas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    No effect of male courtship intensity on female remating in the butterfly Pieris napi.2005Ingår i: Journal of insect behavior, ISSN 0892-7553, E-ISSN 1572-8889, Vol. 18, nr 4, s. 479-489Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In Pieris napi, female fitness increases with number of matings, but wild females mate at an unexpectedly low rate. From a sexual conflict perspective this could be because males manipulate female remating, or alternatively, because wild females experience costs associated with remating which are not applicable under laboratory conditions. To get an indication which sex controls remating and/or the different sexes’ relative costs and benefits of remating, we here test whether female mating frequency is affected by male courtship intensity. We found no effect on female mating frequency or lifespan. This indicates that (i) females control remating and their optimal mating frequency is lower compared to males, or (ii) males can manipulate female remating. We argue that both these alternatives may apply simultaneously to P. napiand that they are inseparable.

  • 18.
    Bergström, Jonas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Enfjäll, Karin
    Determinants of mating rate in a butterfly.Ingår i: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762Artikel i tidskrift (Refereegranskat)
  • 19.
    Bergström, Jonas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Kaitala, Arja
    Natural variation in female mating frequency in a polyandrous butterfly: effects of size and age.2002Ingår i: Animal Behaviour, Vol. 64, s. 49-54Artikel i tidskrift (Refereegranskat)
  • 20. Blanckenhorn, Wolf U
    et al.
    Dixon, Anthony FG
    Fairbairn, Daphne J
    Foellmer, Matthias W
    Gibert, Patricia
    van der Linde, Kim
    Meier, Rudolf
    Nylin, Sören
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Pitnick, Scott
    Schoff, Christopher
    Signorelli, Martino
    Teder, Tiit
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Proximate causes of Rensch's rule: Does sexual size dimorphism in arthropods result from sex differences in development time?2007Ingår i: American Naturalist, Vol. 169, nr 2, s. 245-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 21.
    Dinca, Vlad
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Lukhtanov, V. A.
    Kodandaramaiah, U.
    Norén, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Dapporto, L.
    Wahlberg, N.
    Vila, R.
    Friberg, Mange
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Reproductive isolation and patterns of genetic differentiation in a cryptic butterfly species complex2013Ingår i: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 26, nr 10, s. 2095-2106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Molecular studies of natural populations are often designed to detect and categorize hidden layers of cryptic diversity, and an emerging pattern suggests that cryptic species are more common and more widely distributed than previously thought. However, these studies are often decoupled from ecological and behavioural studies of species divergence. Thus, the mechanisms by which the cryptic diversity is distributed and maintained across large spatial scales are often unknown. In 1988, it was discovered that the common Eurasian Wood White butterfly consisted of two species (Leptidea sinapis and Leptidea reali), and the pair became an emerging model for the study of speciation and chromosomal evolution. In 2011, the existence of a third cryptic species (Leptidea juvernica) was proposed. This unexpected discovery raises questions about the mechanisms preventing gene flow and about the potential existence of additional species hidden in the complex. Here, we compare patterns of genetic divergence across western Eurasia in an extensive data set of mitochondrial and nuclear DNA sequences with behavioural data on inter- and intraspecific reproductive isolation in courtship experiments. We show that three species exist in accordance with both the phylogenetic and biological species concepts and that additional hidden diversity is unlikely to occur in Europe. The Leptidea species are now the best studied cryptic complex of butterflies in Europe and a promising model system for understanding the formation of cryptic species and the roles of local processes, colonization patterns and heterospecific interactions for ecological and evolutionary divergence.

  • 22. Esperk, Toomas
    et al.
    Stefanescu, Constanti
    Teder, Tiit
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Kaasik, Ants
    Tammaru, Toomas
    Distinguishing between anticipatory and responsive plasticity in a seasonally polyphenic butterfly2013Ingår i: Evolutionary Ecology, ISSN 0269-7653, E-ISSN 1573-8477, Vol. 27, nr 2, s. 315-332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Seasonal generations of short-lived organisms often differ in their morphological, behavioural and life history traits, including body size. These differences may be either due to immediate effects of seasonally variable environment on organisms (responsive plasticity) or rely on presumably adaptive responses of organisms to cues signalizing forthcoming seasonal changes (anticipatory plasticity). When directly developing individuals of insects are larger than their overwintering conspecifics, the between-generation differences are typically ascribed to responsive plasticity in larval growth. We tested this hypothesis using the papilionid butterly Iphiclides podalirius as a model species. In laboratory experiments, we demonstrated that seasonal differences in food quality could not explain the observed size difference. Similarly, the size differences are not likely to be explained by the immediate effects of ambient temperature and photoperiod on larval growth. The qualitative pattern of natural size differences between the directly developing and diapausing butterflies could be reproduced in the laboratory as a response to photoperiod, indicating anticipatory character of the response. Directly developing and diapausing individuals followed an identical growth trajectory until the end of the last larval instar, with size differences appearing just a few days before pupation. Taken together, various lines of evidence suggest that between-generation size differences in I. podalirius are not caused by immediate effects of environmental factors on larval growth. Instead, these differences rather represent anticipatory plasticity and are thus likely to have an adaptive explanation. It remains currently unclear, whether the seasonal differences in adult size per se are adaptive, or if they constitute co-product of processes related to the diapause. Our study shows that it may be feasible to distinguish between different types of plasticity on the basis of empirical data even if fitness cannot be directly measured, and contributes to the emerging view about the predominantly adaptive nature of seasonal polyphenisms in insects.

  • 23.
    Fogelström, Elsa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Olofsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Posledovich, Diana
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Dahlgren, Johan P.
    Ehrlén, Johan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för ekologi, miljö och botanik.
    Plant-herbivore synchrony and selection on plant flowering phenology2017Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 98, nr 3, s. 703-711Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Temporal variation in natural selection has profound effects on the evolutionary trajectories of populations. One potential source of variation in selection is that differences in thermal reaction norms and temperature influence the relative phenology of interacting species. We manipulated the phenology of the butterfly herbivore Anthocharis cardamines relative to genetically identical populations of its host plant, Cardamine pratensis, and examined the effects on butterfly preferences and selection acting on the host plant. We found that butterflies preferred plants at an intermediate flowering stage, regardless of the timing of butterfly flight relative to flowering onset of the population. Consequently, the probability that plant genotypes differing in timing of flowering should experience a butterfly attack depended strongly on relative phenology. These results suggest that differences in spring temperature influence the direction of herbivore-mediated selection on flowering phenology, and that climatic conditions can influence natural selection also when phenotypic preferences remain constant.

  • 24. Friberg, M.
    et al.
    Posledovich, Diana
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Decoupling of female host plant preference and offspring performance in relative specialist and generalist butterflies2015Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 178, nr 4, s. 1181-1192Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The preference-performance hypothesis posits that the host plant range of plant-feeding insects is ultimately limited by larval costs associated with feeding on multiple resources, and that female egg-laying preferences evolve in response to these costs. The trade-off of either using few host plant species and being a strong competitor on them due to effective utilization or using a wide host plant range but being a poor competitor is further predicted to result in host plant specialization. This follows under the hypothesis that both females and offspring are ultimately favoured by utilizing only the most suitable host(s). We develop an experimental approach to identify such trade-offs, i.e. larval costs associated with being a host generalist, and apply a suite of experiments to two sympatric and syntopic populations of the closely related butterflies Pieris napi and Pieris rapae. These butterflies show variation in their level of host specialization, which allowed comparisons between more and less specialized species and between families within species. Our results show that, first, the link between female host preference and offspring performance was not significantly stronger in the specialist compared to the generalist species. Second, the offspring of the host plant specialist did not outperform the offspring of the generalist on the former's most preferred host plant species. Finally, the more generalized species, or families within species, did not show higher survival or consistently higher growth rates than the specialists on the less preferred plants. Thus, the preference and performance traits appear to evolve as largely separated units.

  • 25.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Aalberg Haugen, Inger M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Dahlerus, Josefin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Asymmetric life-history decision-making in butterfly larvae2011Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 165, nr 2, s. 301-310Artikel i tidskrift (Refereegranskat)
    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.

  • 26.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Bergman, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Wahlberg, Niklas
    Kullberg, Jakkoo
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Niche separation in space and time between two sympatric sister species—a case of ecological pleiotropy2008Ingår i: Evolutionary Ecology, ISSN 0269-7653Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract We investigate the niche separation in space and time between the Palearctic sister species Leptidea sinapis and L. reali (Lepidoptera, Pieridae) in central Sweden. Using field sampling, we show that L. reali is a habitat specialist confined to meadows, whereas L. sinapis is a habitat generalist also inhabiting forests. This difference in habitat utilization was corroborated by experimental release of laboratory-reared L. sinapis and L. reali in two adjacent forest and meadow habitats during their natural flight period; virtually all recaptured L. reali that were released in the forest were later caught in the meadow, whereas L. sinapis shifted equally often from meadow to forest as in the opposite direction. In the field, both species fly in May–June, but L. reali appears on average a week earlier in spring and has a substantial second generation in July, whereas L. sinapis is practically univoltine. When overwintered pupae were incubated under identical conditions in the laboratory, females did, however, not differ in phenology, and L. sinapis males actually emerged earlier than L. reali males. When larvae were reared at 23°C on the host plant Lotus corniculatus at a range of daylengths, both species produced a substantial proportion of directly developing individuals at an 18.5 h daylength or longer. When reared at 23°C and a 22 h daylength, L. reali showed an overall higher propensity to develop directly than L. sinapis on plant species originating from both the meadow and the forest habitat. Both Leptidea species showed a lower propensity to enter direct development on forest associated plants than on meadow associated plants. Hence, we suggest that the difference in phenology and voltinism between L. sinapis and L. reali is largely the result of environmentally implemented ecological pleiotropic effects caused by the between-species difference in habitat preference.

  • 27.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Dahlerus, Josefin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Strategic larval decision-making in a bivoltine butterfly2012Ingår i: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 169, nr 3, s. 623-635Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In temperate areas, insect larvae must decide between entering winter diapause or developing directly and reproducing in the same season. Long daylength and high temperature promote direct development, which is generally associated with a higher growth rate. In this work, we investigated whether the larval pathway decision precedes the adjustment of growth rate (state-independent), or whether the pathway decision is conditional on the individual's growth rate (state-dependent), in the butterfly Pieris napi. This species typically makes the pathway decision in the penultimate instar. We measured growth rate throughout larval development under two daylengths: slightly shorter and slightly longer than the critical daylength. Results indicate that the pathway decision can be both state-independent and state-dependent; under the shorter daylength condition, most larvae entered diapause, and direct development was chosen exclusively by a small subset of larvae showing the highest growth rates already in the early instars; under the longer daylength condition, most larvae developed directly, and the diapause pathway was chosen exclusively by a small subset of slow-growing individuals. Among the remainder, the choice of pathway was independent of the early growth rate; larvae entering diapause under the short daylength grew as fast as or faster than the direct developers under the longer daylength in the early instars, whereas the direct developers grew faster than the diapausers only in the ultimate instar. Hence, the pathway decision was state-dependent in a subset with a very high or very low growth rate, whereas the decision was state-independent in the majority of the larvae, which made the growth rate adjustment downstream from the pathway decision.

  • 28.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Kodandaramaiah, Ullasa
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Norén, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wahlberg, Niklas
    Department of Biology, University of Turku.
    Genetic differentiation and phylogeographic patterns in European populations of Leptidea sinapis and L. realiManuskript (preprint) (Refereegranskat)
    Abstract [en]

    The direction of a coevolutionary interaction can differ between local populations as in the butterflies Leptidea sinapis and L. reali. The morphologically virtually identical sister-species have partitioned their niches differently in different parts of their distribution by shifting habitat specialist and generalist roles between different sympatric areas. Hence, a species that is a generalist in some areas can be a local specialist in others, and vice versa. We have sequenced the mitochondrial COI gene from specimens collected across Europe in order to (i) describe the between-species variation over a large area, (ii) identify possible glacial refugia and re-colonisation routes to obtain a phylogeographic hypothesis for explaining the geographic mosaic of niche separation and (iii) apply a population genetic approach to determine the level of intraspecific genetic differentiation. The results show evidence for species distinctiveness throughout Europe. Only small variation was found in L. reali, whereas the haplotype network of L. sinapis showed a deep division into two haplotype families of which one was restricted to Spain and the other was widespread over the continent (including Spain). The widespread haplotype family was divided into two common variants, one eastern and one western, each being surrounded by rare haplotypes. The both deep and shallow genetic differentiation implies that L. sinapis might have been divided into different refugia during several glaciations. Both species showed significant genetic differentiation in pairwise ФST, and as habitat generalist populations could differ significantly from other habitat generalist populations but not from habitat specialist populations, we conclude that this study supports that the geographic mosaic of niche separation is caused by local processes rather than common ancestry of local habitat generalists or specialists within each species

  • 29.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Uppsala universitet.
    Leimar, Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Heterospecific courtship, minority effects and niche separation between cryptic butterfly species2013Ingår i: Journal of Evolutionary Biology, ISSN 1010-061X, E-ISSN 1420-9101, Vol. 26, nr 5, s. 971-979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Species interacting in varied ecological conditions often evolve in different directions in different local populations. The butterflies of the cryptic Leptidea complex are sympatrically distributed in different combinations across their Eurasian range. Interestingly, the same species is a habitat generalist in some regions and a habitat specialist in others, where a sibling species has the habitat generalist role. Previous studies suggest that this geographically variable niche divergence is generated by local processes in different contact zones. By varying the absolute and relative densities of Leptidea sinapis and Leptidea juvernica in large outdoor cages, we show that female mating success is unaffected by conspecific density, but strongly negatively affected by the density of the other species. Whereas 80% of the females mated when a conspecific couple was alone in a cage, less than 10% mated when the single couple shared the cage with five pairs of the other species. The heterospecific courtships can thus affect the population fitness, and for the species in the local minority, the suitability of a habitat is likely to depend on the presence or absence of the locally interacting species. If the local relative abundance of the different species depends on the colonization order, priority effects might determine the ecological roles of interacting species in this system.

  • 30.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Olofsson, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Berger, David
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Karlsson, Bengt
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Habitat choice precedes host plant choice - niche separation in a species pair of a generalist and a specialist butterfly2008Ingår i: Oikos, Vol. 117, nr 9, s. 1337-1344Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The sister species Leptidea reali and L. sinapis have partitioned their niches differently in different parts of their sympatric distribution. In Spain and France L. sinapis is a widespread generalist whereas L. reali is specialized on high altitude open areas. Interestingly, the reverse is true in Ireland and the Czech Republic where L. reali is widespread and L. sinapis specialized on meadows. In Sweden, L. reali is a habitat specialist confined to meadows, whereas L. sinapis is a habitat generalist also inhabiting forests. Ultimately, the geographic mosaic of niche separation is the result of local processes in each contact zone or a secondary effect of the host plant distribution, if L. sinapis and L. reali prefer different legume host plants. Hence, in Sweden L. sinapis might utilize the forest habitat either due to a wider habitat preference or due to a wider host plant preference than L. reali. Studies of wild butterflies showed that L. sinapis laid 26% of their eggs on forest-associated legumes compared to 6% in L. reali, although laboratory experiments showed that both species had virtually identical host plant preferences strongly preferring the meadow-associated legume Lathyrus pratensis. Furthermore, flight duration tests in a variety of temperatures demonstrated a between-species difference; L. sinapis females reached their flight optimum at a lower temperature than L. reali females. The lower L. sinapis flight temperature optimum is most probably a secondary effect due to habitat-specific selection, and therefore a consequence rather than the cause of the habitat partitioning. The finding that habitat choice precedes host plant choice suggests that the European geographic mosaic of niche separation, with L. sinapis and L. reali shifting habitat specialist/generalist roles, is not caused by rigid between-species differences in a related niche parameter, but instead is a result of local processes within each secondary contact zone.

  • 31.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk ekologi.
    Vongvanich, Namphung
    Borg-Karlsson, Anna-Karin
    Kemp, Darrell
    Merilaita, Sami
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Female mate choice determines reproductive isolation between sympatric butterflies2008Ingår i: Behavioral Ecology and Sociobiology, Vol. 62, s. 873-886Artikel i tidskrift (Refereegranskat)
  • 32. Friberg, Magne
    et al.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Butterflies and plants: preference/performance studies in relation to plant size and the use of intact plants vs. cuttings2016Ingår i: Entomologia Experimentalis et Applicata, ISSN 0013-8703, E-ISSN 1570-7458, Vol. 160, nr 3, s. 201-208Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Plants have evolved a number of defences to ameliorate herbivore attacks including chemicals induced by mechanical wounding. Such changes in plant chemical composition are potential confounding factors in experiments on plant-insect interactions, which often present cuttings of potential host plants to phytophagous insects. In particular, this could affect studies of female egg-laying preference and larval performance, because the same plant chemicals that deter certain generalist insects can elevate attacks from more specialized insects. Furthermore, plant cuttings are by definition smaller than intact plants, and any female host size preference could thus affect experiments using plant cuttings. We first assessed female preference and larval performance of a specialist herbivore, Pieris napi (L.) (Lepidoptera: Pieridae, Pierini), confronted with either intact plants or leaf-cuttings of four Brassicaceae host plants, Alliaria petiolata (Bieb.) Cavara & Grande, Barbarea vulgaris (L.) WT Aiton, Berteroa incana (L.) DC., and Brassica napus (L.). Egg and larval survival did not differ between intact plants and leaf-cuttings, whereas larval growth was slightly, but significantly, faster on leaf-cuttings. Females, however, significantly preferred to lay eggs on intact plants of all four hosts, although the preference hierarchy for the intact plants was largely mirrored by that for leaf-cuttings. We then tested the female preference for different size-classes of intact B. napus plants. Small individuals received more eggs than larger individuals, and follow-up experiments showed that this difference was largely generated by a strong female preference for cotyledon leaves; there was no significant difference in female preference for large and small individuals when both carried cotyledons, and females landing on cotyledons were more likely to oviposit compared to when landing on a true leaf. Our study concludes that plant cuttings can serve as adequate proxies for live plants for preference/performance studies, but that experimentalists should be aware of the variation imposed both by plant handling and plant phenology for female oviposition preference.

  • 33.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Evolutionär ekologi.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Evolutionär ekologi.
    Generation-dependent female choice: behavioral polyphenism in a bivoltine butterfly2007Ingår i: Behavioral Ecology, ISSN 1045-2249, Vol. 18, nr 4, s. 758-763Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Climatic and biotic circumstances vary as seasons shift, and different cohorts of multivoltine species are likely subjected to different selection regimes. The bivoltine butterfly Leptidea reali (Re´al’s wood white; Lepidoptera: Pieridae) appears during May and June in central Sweden and has a partial second generation in late July. We manipulated both generations to appear simultaneously and performed laboratory mating experiments that showed the presence of a behavioral polyphenism in mating propensity, which is induced during the developmental stages. Females of the summer generation expressed higher mating propensities than spring generation females. Spring females showed an increase in mating propensity with increasing age, whereas summer females accepted most matings already when they were only 1 or 2 days old. It is likely that larval time constraints, a lower abundance of males and a lower risk of accepting a male of their univoltine sister species Leptidea sinapis (wood white), have relaxed selection on mate discrimination among summer generation females. A major challenge for future research is to further investigate the developmental pathways causing the polyphenism and the adaptive implications of cohort dependent behaviors.

  • 34.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Host plant induced larval decision-making in a habitat/host plant generalist butterfly2010Ingår i: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 91, s. 15-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phenotypic plasticity can be a passive response to fluctuating environmental conditions or an active and presumably adaptive (evolved) response selected for in different environments. Here we ask if the larval decision to enter diapause when reared on a host plant associated with a colder habitat is an active or a passive response to host plant quality or suitability. We compare plasticity in larval propensity to enter diapause of the habitat generalist butterfly Leptidea sinapis and the meadow specialist Leptidea reali in a range of temperatures and long daylength on a forest plant, Lathyrus linifolius, and a meadow-associated plant, Lathyrus pratensis. The warmer meadow habitat promotes direct development whereas the colder forest habitat is conducive to diapause. Larvae of L. sinapis had a higher propensity to enter diapause when reared on the forest plant L. linifolius across all temperatures. Conversely, the propensity of L. reali to enter diapause was consistently lower and did not differ between host plants. Larval growth rates were similar between and within butterfly species and between host plants. Hence, we conclude that larval pathway decision-making in L. sinapis is an active response mediated by information from their host plants.

  • 35.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Host plant preference and performance of the sibling species of butterflies Leptidea sinapis and Leptidea reali: a test of the trade-off hypothesis for food specialisation.2009Ingår i: Oecologia, ISSN 0029-8549, Vol. 159, nr 1, s. 127-137Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A large proportion of phytophagous insect species are specialised on one or a few host plants, and female host plant preference is predicted to be tightly linked to high larval survival and performance on the preferred plant(s). Specialisation is likely favoured by selection under stable circumstances, since different host plant species are likely to differ in suitability-a pattern usually explained by the "trade-off hypothesis", which posits that increased performance on a given plant comes at a cost of decreased performance on other plants. Host plant specialisation is also ascribed an important role in host shift speciation, where different incipient species specialise on different host plants. Hence, it is important to determine the role of host plants when studying species divergence and niche partitioning between closely related species, such as the butterfly species pair Leptidea sinapis and Leptidea reali. In Sweden, Leptidea sinapis is a habitat generalist, appearing in both forests and meadows, whereas Leptidea reali is specialised on meadows. Here, we study the female preference and larval survival and performance in terms of growth rate, pupal weight and development time on the seven most-utilised host plants. Both species showed similar host plant rank orders, and larvae survived and performed equally well on most plants with the exceptions of two rarely utilised forest plants. We therefore conclude that differences in preference or performance on plants from the two habitats do not drive, or maintain, niche separation, and we argue that the results of this study do not support the trade-off hypothesis for host plant specialisation, since the host plant generalist Leptidea sinapis survived and performed as well on the most preferred meadow host plant Lathyrus pratensis as did Leptidea reali although the generalist species also includes other plants in its host range.

  • 36. Friberg, Magne
    et al.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Host preference variation cannot explain microhabitat differentiation among sympatric Pieris napi and Pieris rapae butterflies2019Ingår i: Ecological Entomology, ISSN 0307-6946, E-ISSN 1365-2311, Vol. 44, nr 4, s. 571-576Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1. Often, closely related insect species feed on different host plant species, and the tremendous diversity of phytophagous insects is therefore attributed to host plant-driven speciation. However, for most taxa, host use information comes from field observations of egg-laying females or feeding caterpillars, which means that the underlying reason for a particular host-affiliation is not easily determined. 2. Therefore, it is often unclear whether an insect feeds on a certain host because it prefers that plant to alternative hosts, or because the host distribution overlaps with the habitat requirements of the insect. 3. We ask to what extent a divergent host use in the field mirrors the host plant preferences of two closely related butterflies, Pieris napi and Pieris rapae (Pieridae). In nature, P. napi typically occurs in moister habitats than P. rapae. 4. We scanned several microhabitats at a field site in Southern Sweden during multiple years, and collected Pieris eggs from three different plants, Cardamine pratensis (wet meadows), Barbarea vulgaris (drier micro-habitats) and Alliaria petiolata (intermediate areas). 5. As predicted, P. rapae eggs were more common than P. napi eggs on B. vulgaris, whereas all of the 358 individuals collected from C. pratensis were P. napi, indicating a divergence in host use between the Pieris species. However, under controlled laboratory conditions, both species had virtually identical oviposition preferences, laying eggs on all three plants, notably P. rapae also laying eggs on C. pratensis, indicating that habitat use, not plant preference, drives host plant use in nature.

  • 37.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för zoologisk ekologi. Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för zoologisk ekologi.
    Nya rön om skogs- och ängsvitvingar: Vem är vem i fjärilsvärlden?2009Ingår i: Flora och Fauna, Vol. 104, nr 1, s. 12-17Artikel, forskningsöversikt (Övrig (populärvetenskap, debatt, mm))
  • 38.
    Friberg, Magne
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Leimar, Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Heterospecific courtships, Allee-effects and niche separation between Leptidea sinapis and Leptidea realiManuskript (preprint) (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Increasing attention is given to coevolutionary studies and to the role of ecology in local adaptation. The coevolutionary process can act in parallel throughout the distribution of species that interact in similar ecologies, whereas species interacting in varied ecological conditions might coevolve in different directions in different local populations. The butterflies Leptidea sinapis and L. reali have partitioned their niches differently in different parts of their sympatric distribution, with one species being a local habitat generalist in several different regions, and a local specialist in other areas where the sister species has adopted the habitat generalist role. Niche separation is likely independent of resource competition in this phytophagous system, and we study the potential for heterospecific sexual interference competition to redefine the suitability of a habitat and select for niche separation. We used the average female mating success in large outdoor cage experiments that varied both the absolute and relative density of the two species to estimate potential fitness costs of being in local minority. The mating success was unaffected by absolute density (conspecifics/m2) but strongly affected by the proportion of con- and heterospecifics in each cage. The proportion of mated females was ten times higher when a conspecific couple spent the day alone in the cage compared to when the single couple shared the cage with five heterospecific pairs. Being in the minority thus resulted in strong sexual interference from the locally more common competitor. We propose that these Allee effects select for habitat specialisation in the locally rare species as individuals leaving the core population likely suffer decreased fitness from spending time in heterospecific courtship. Hence, habitat suitability might depend less on local resource availability and more on the presence or absence of a local sexual competitor in this system.

  • 39. Gibbs, Melanie
    et al.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Van Dyck, Hans
    Phenotypic plasticity in butterfly morphology in response to weather conditions during development2011Ingår i: Journal of Zoology, ISSN 0952-8369, E-ISSN 1469-7998, Vol. 283, nr 3, s. 162-168Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In seasonal environments, phenotypic plasticity in response to gradual changes in environmental variables may result in the production of discrete seasonal morphs. Production of the appropriate seasonal morph at the correct time relies on individuals interpreting environmental cues during their development. The speckled wood butterfly Pararge aegeria (L.) has previously been shown to have developmental and phenotypic plasticity across seasons and space (habitats). Here, we examine the developmental sensitivity of different seasonal cohorts of female P. aegeria to changes in local weather conditions over time (1989–1999) and determine how such temporal climatic variation affects adult phenotype development. We observed trait- and cohort-specific changes of adult phenotype development in response to local temporal changes in temperature and rainfall levels. We discuss our findings using current life-history theory and consider the potential for changes in local weather conditions to influence population variability in butterfly morphology and performance

  • 40. Gibbs, Melanie
    et al.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Van Dyck, Hans
    Temperature, rainfall and butterfly morphology: does life history theory match the observed pattern?2011Ingår i: Ecography, ISSN 0906-7590, E-ISSN 1600-0587, Vol. 34, nr 2, s. 336-344Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Butterfly distribution and abundance is known to be influenced by temperature and rainfall. What is not clear, however, is how life history and flight morphological traits are affected by changes in local weather conditions. During the period 1989-1999, we explored the effects of ambient temperature and rainfall during larval development on adult phenotypic traits (body mass, forewing loading, forewing surface area and forewing length) in a Swedish population of the speckled wood butterfly Pararge aegeria. As different seasonal cohorts correspond to different developmental pathways (larval hibernating, pupal hibernating and directly developing), we analysed these morphological time series relative to developmental pathway. Phenotypic variation in response to the temperature and rainfall levels experienced during larval development differed in both magnitude and direction depending on the developmental pathway, and hence seasonal cohort, examined (i.e. there was a pathway-specific response). We suggest that through its developmental flexibility P. aegeria may be able to adjust to variation in weather conditions over time. Other less flexible species, however, may not be so fortunately buffered. To truly estimate the impact of climate change on biodiversity more fine-scale, local studies are required that examine the mechanisms underlying the response of species to climate change.

  • 41.
    Gotthard, Karl
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Nylin, Sören
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Individual state controls temperature dependence in a butterfly (Lasiommata maera)2000Ingår i: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 267, nr 1443, s. 589-93Artikel i tidskrift (Refereegranskat)
    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.

  • 42.
    Hill, Jason
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik. Uppsala University, Sweden.
    Rastas, Pasi
    Hornett, Emily A.
    Neethiraj, Ramprasad
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Clark, Nathan
    Morehouse, Nathan
    de la Paz Celorio-Mancera, Maria
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Carnicer Cols, Jofre
    Dircksen, Heinrich
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för funktionell zoomorfologi.
    Meslin, Camille
    Keehnen, Naomi
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Pruisscher, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Sikkink, Kristin
    Vives, Maria
    Vogel, Heiko
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Woronik, Alyssa
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik. New York University, USA.
    Boggs, Carol L.
    Nylin, Sören
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Wheat, Christopher W.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen, Avdelningen för populationsgenetik.
    Unprecedented reorganization of holocentric chromosomes provides insights into the enigma of lepidopteran chromosome evolution2019Ingår i: Science Advances, E-ISSN 2375-2548, Vol. 5, nr 6, artikel-id eaau3648Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 43.
    Johan, Andersson
    et al.
    KTH.
    Borg-Karlson, Anna-Karin
    KTH.
    Vongvanich, Namphung
    KTH.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Ekologiska avdelningen.
    Male sex pheromone release and female mate choice in a butterfly2007Ingår i: Journal of Experimental Biology, Vol. 210, nr 6, s. 964-970Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    In butterflies female mate choice is influenced by both visual and olfactory cues, the latter of which are important at close range. Males of the green-veined butterfly, Pieris napi, are known to release citral (mixture of geranial and neral, 1:1), but its role(s) and conditions of release are not known. Here, we show that male P. napi release citral when interacting with conspecific males, conspecific females, heterospecific males and also when alone. The amount of citral released correlated strongly with male flight activity, which explained more than 70% of the variation. This suggests that males do not exercise control over turning release on or off, but rather that citral is emitted as a passive physical process during flight. Electroantennogram experiments showed that female antennal response was ten times more sensitive to citral than male response. Females expressed acceptance behavior when exposed to models made with freshly excised male wings or those treated with citral following chemical extraction, but not to ones with extracted wings only. Hence, these behavioral and electrophysiological tests provide strong evidence that citral is a signal from the male directed to the female during courtship, and that it functions as a male sex pheromone.

  • 44.
    Karlsson, Bengt
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Stjernholm, Fredrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Test of a developmental trade-off in a polyphenic butterfly: direct development favours reproductive output2008Ingår i: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 22, nr 1, s. 121-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    1.Evolutionary theory predicts that resource allocation decisions taken during development are adjusted to an organism's life-history. These decisions may have irreversible effects on body design and strong fitness consequences. Holometabolous insects that have a long expected life span typically postpone reproduction, and so are expected to allocate resources for somatic maintenance prior to investing in reproduction. In contrast, insects that have a short expected life span are expected to allocate relatively less to soma and more to reproduction. In support of this theory, an earlier investigation of resources allocated to soma vs. reproductive reserves in the comma butterfly, Polygonia c-album, revealed that short-lived females indeed allocate more resources to reproductive reserves as compared to longer lived females that hibernate before reproduction suggesting that short-lived females should have higher fecundity.

    2. Here we test this prediction, using the comma butterfly as our study organism. Depending on daylength and temperature this butterfly produces one of two morphs: (i) a light summer morph that reproduces directly after adult eclosion and has a short expected life span of a couple of weeks; or (ii) a darker winter morph that normally lives for 8–9 months before the onset of reproduction. Our test is based on experimental manipulation that allowed us to induce reproduction without prior hibernation in winter morph comma butterflies, and comparing lifetime fecundity among three groups: (i) directly reproducing summer morph commas; (ii) directly reproducing winter morph commas; and (iii) winter morph commas reproducing after overwintering. This protocol allowed us to tease apart trade-offs during development and the hibernation period.

    3. The results showed that the short-lived summer morph had a substantially higher fecundity (total number of eggs = 586 ± 19, mean ± SE) than the winter morph females manipulated to reproduce without hibernation (total number of eggs = 334 ± 42). We argue that this is a consequence of a resource allocation trade-off during early development observed in this species; females with a short expected life as adults allocate relatively more of their resources to reproductive parts and thereby reach a higher reproductive output compared to females predisposed for a long adult life.

    4. There was no significant difference in lifetime fecundity between winter morph females that did, or did not, hibernate before reproduction. This suggests that the cost of hibernation per se is small and hence corroborates our conclusion that the life-history implemented trade-off made during early development underlies the lower reproductive output of the winter morph butterflies.

  • 45.
    Kazemi, Baharan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gamberale-Stille, Gabriella
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wåtz, Therese
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Leimar, Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Learning of salient prey traits explains Batesian mimicry evolution2018Ingår i: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 72, nr 3, s. 531-539Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Batesian mimicry evolution involves an initial major mutation that produces a rough resemblance to the model, followed by smaller improving changes. To examine the learning psychology of this process, we applied established ideas about mimicry in Papilio polyxenes asterius of the model Battus philenor. We performed experiments with wild birds as predators and butterfly wings as semiartificial prey. Wings of hybrids of P. p. asterius and Papilio machaon were used to approximate the first mutant, with melanism as the hypothesized first mimetic trait. Based on previous results about learning psychology and imperfect mimicry, we predicted that: melanism should have high salience (i.e., being noticeable and prominent), meaning that predators readily discriminate a melanistic mutant from appearances similar to P. machaon; the difference between the first mutant and the model should have intermediate salience to allow further improvement of mimicry; and the final difference in appearance between P. p. asterius and B. philenor should have very low salience, causing improvement to level off. Our results supported both the traditional hypothesis and all our predictions about relative salience. We conclude that there is good agreement between long-held ideas about how Batesian mimicry evolves and recent insights from learning psychology about the role of salience in mimicry evolution.

  • 46.
    Kemp, Darrell
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk Ekologi.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. Zoologisk Ekologi.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen. 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.2006Ingår i: Ethology, ISSN 0179-1613, Vol. 112, nr 5, s. 471-477Artikel i tidskrift (Refereegranskat)
    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.

  • 47. Khihon Rokhas, Maria
    et al.
    Liljestrand Rönn, Johanna
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Emmer, Åsa
    Analysis of butterfly reproductive proteins using capillary electrophoresis and mass spectrometry2019Ingår i: Analytical Biochemistry, ISSN 0003-2697, E-ISSN 1096-0309, Vol. 566, s. 23-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A method for analysis of proteins from spermatophores transferred from male to female Pieris napi butterflies during mating has been developed. The proteins were solubilized from the dissected spermatophores using different solubilization agents (water, methanol, acetonitrile and hexafluoroisopropanol). Capillary electrophoresis (CE) analysis was performed using an acidic background electrolyte containing a fluorosurfactant to avoid protein-wall adsorption, and to increase separation performance. The samples were also analyzed with matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS), in a lower m/z range (1000-6000) and a higher m/z range (6000-12000). Solubilization with different solvents and the use of alternative matrices gave partly complementary profiles.

  • 48.
    Kivelä, Sami M.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Friberg, Magne
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Adaptive developmental plasticity in a butterfly: mechanisms for size and time at pupation differ between diapause and direct development2017Ingår i: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 122, nr 1, s. 46-57Artikel i tidskrift (Refereegranskat)
    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.

  • 49.
    Kivelä, Sami M.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Friberg, Magne
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Leimar, Olof
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Gotthard, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Towards a mechanistic understanding of insect life history evolution: oxygen-dependent induction of moulting explains moulting sizes2016Ingår i: Biological Journal of the Linnean Society, ISSN 0024-4066, E-ISSN 1095-8312, Vol. 117, nr 3, s. 586-600Artikel i tidskrift (Refereegranskat)
    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.

  • 50.
    Kodandaramaiah, Ullasa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Wiklund, Christer
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Vallin, Adrian
    Stockholms universitet, Naturvetenskapliga fakulteten, Zoologiska institutionen.
    Fixed eyespot display in a butterfly thwarts attacking birds2009Ingår i: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 77, nr 6, s. 1415-1419Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Eyespots have evolved in many lepidopteran insects, which suggests their adaptive value. One of their hypothesized functions is that predators are intimidated by prey with large and conspicuous eyespots and hence refrain from attacking them. Recent experiments have shown that a combination of eyespots and intimidating behaviour can increase survival. We tested whether the mere presence of conspicuous eyespots can thwart attacking birds, that is, when the eyespots are displayed constantly, without any intimidating behaviour. We used prey that consisted of wings of the peacock pansy butterfly, Junonia almana, glued onto a piece of cardboard so as to resemble a butterfly with its wings open. A mealworm was placed between the wings in place of the body. Great tits, Parus major, were used as the predator in the study and were offered a choice between two model prey, one with intact eyespots and one without. Prey with eyespots were attacked significantly fewer times than those without. The time between the first and second attack was longer when the prey without eyespots was attacked first. These results support the hypothesis that naturally occuring butterfly eyespots can increase survival even when they are constantly displayed and motionless.

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