I am course leader and teach at the second year ecology course (Ecology II). In addition I lecture at several other courses in Ecology, Evolution and Entomology.

My research concerns the evolutionary ecology of developmental plasticity and life history in insects, primarily butterflies. I am particularly interested in how the diapause decision affects life cycle regulation and how it evolves due to variation in local selction pressures. I also investigate how insect diapause and thermal adaptation affects spring phenology and interactions between butterflies and their host plants, and to what extent the diapause decision allows the evolution of partly independent developmental pathways. My group is also exploring the gentic background to adaptive variation in seasonal plasticity. We are studying this in several different butterfly species using a wide range of methods from field experiment to genomics.

My Research is funded by grants from The Bolin Centre for Climate Research at Stockholm University and by the Swedish Research Council (VR).

Presently I am supervising three Ph.D students, Mats Ittonen, Anna Shoshan, and Isabelle Siemers. I also welcome master students and we always have many differnt projects to offer, including both field and lab work.

 

An updated list of my publications can be found here.

 

Previous PhD students:

Dr. David Berger, now running his own group at Uppsala University.

Dr. Inger Aalberg-Haugen, presently working at The Norwegian Institute for Nature Research (NINA).

Dr. Diana Posledovich, at the Swedish Chemicals Agency, Stockholm.

Dr. Peter Pruisscher, at the SciLifeLab Clinical Genomics, Stockholm 

Dr. Olle Lindestad, Post-doc at the Department of Ecology, Environment and Plant Sciences, Stockholm University in the group of Johan Ehrlén. Here is Olles University page

Previous Post-docs

Dr Richard Walters, presently at The University of Reading and and guest researcher at Lund University.

Dr. Sami Kivelä, presently a Finnish Academy Research Fellow at University of Oulo, Finland.

Dr. Phlipp Lehmann, running his at own group as Full Professor at University of Greifswald, Germany.

Dr. Matthew E. Nielsen, running his own group as Assistant Professor at the University of Bremen, Germany.

A selection from Stockholm University publication database

• Seasonal specialization drives divergent population dynamics in two closely related butterflies

  2023. Loke von Schmalensee (et al.). Nature Communications 14

  Article

  Seasons impose different selection pressures on organisms through contrasting environmental conditions. How such seasonal evolutionary conflict is resolved in organisms whose lives span across seasons remains underexplored. Through field experiments, laboratory work, and citizen science data analyses, we investigate this question using two closely related butterflies (Pieris rapae and P. napi). Superficially, the two butterflies appear highly ecologically similar. Yet, the citizen science data reveal that their fitness is partitioned differently across seasons. Pieris rapae have higher population growth during the summer season but lower overwintering success than do P. napi. We show that these differences correspond to the physiology and behavior of the butterflies. Pieris rapae outperform P. napi at high temperatures in several growth season traits, reflected in microclimate choice by ovipositing wild females. Instead, P. rapae have higher winter mortality than do P. napi. We conclude that the difference in population dynamics between the two butterflies is driven by seasonal specialization, manifested as strategies that maximize gains during growth seasons and minimize harm during adverse seasons, respectively.

  Read more about Seasonal specialization drives divergent population dynamics in two closely related butterflies

• Local adaptation to seasonal cues at the fronts of two parallel, climate-induced butterfly range expansions

  2022. Mats Ittonen (et al.). Ecology Letters 25 (9), 2022-2033

  Article

  Climate change allows species to expand polewards, but non-changing environmental features may limit expansions. Daylength is unaffected by climate and drives life cycle timing in many animals and plants. Because daylength varies over latitudes, poleward-expanding populations must adapt to new daylength conditions. We studied local adaptation to daylength in the butterfly Lasiommata megera, which is expanding northwards along several routes in Europe. Using common garden laboratory experiments with controlled daylengths, we compared diapause induction between populations from the southern-Swedish core range and recently established marginal populations from two independent expansion fronts in Sweden. Caterpillars from the northern populations entered diapause in clearly longer daylengths than those from southern populations, with the exception of caterpillars from one geographically isolated population. The northern populations have repeatedly and rapidly adapted to their local daylengths, indicating that the common use of daylength as seasonal cue need not strongly limit climate-induced insect range expansions.

  Read more about Local adaptation to seasonal cues at the fronts of two parallel, climate-induced butterfly range expansions

• Longer and warmer prewinter periods reduce post-winter fitness in a diapausing insect

  2022. Matthew E. Nielsen, Philipp Lehmann, Karl Gotthard. Functional Ecology 36 (5), 1151-1162

  Article

  1. Diapause is considered an important adaptation for survival of winter; however, insects often enter diapause long before its onset. Thus, diapausing insects must also be able to survive these prewinter conditions which warm temperatures could make quite energetically taxing despite relative inactivity.
  2. We tested for both immediate and delayed fitness effects of prewinter conditions in diapausing Pieris napi butterfly pupae, experimentally exposing them to different prewinter treatments in a factorial design. We placed diapausing pupae at one of three temperatures (15, 20 and 25°C) for 1 to 16 weeks, followed by the same standardized winter for all individuals.
  3. We monitored survival of pupae at multiple points during the experiment, including after winter, as well as their change in mass. For a subset of individuals, we also made repeated metabolic measurements.
  4. We found substantial weight loss during prewinter warm periods, greater during longer prewinter treatments at higher temperatures. This weight loss was associated with elevated metabolic rates at higher temperatures which increased over the duration of the prewinter treatment.
  5. Although we found little prewinter mortality associated with these conditions, mortality was much greater post-winter for individuals in long, warm prewinter treatments and the dry mass of adults that did survive these conditions was lower, highlighting the need to understand chronic or delayed effects of stress on fitness.
  6. Ultimately, we found substantial fitness consequences of prewinter conditions for a diapausing insect. Given that climate change will make these prewinter periods both longer and more intense, it will be important to understand how dormant organisms tolerate or reduce the length of these dormant, inactive periods.

  Read more about Longer and warmer prewinter periods reduce post-winter fitness in a diapausing insect

• Local adaptation of life cycles in a butterfly is associated with variation in several circadian clock genes

  2022. Olle Lindestad (et al.). Molecular Ecology 31 (5), 1461-1475

  Article

  Many insects exhibit geographical variation in voltinism, the number of generations produced per year. This includes high-latitude species in previously glaciated areas, meaning that divergent selection on life cycle traits has taken place during or shortly after recent colonization. Here, we use a population genomics approach to compare a set of nine Scandinavian populations of the butterfly Pararge aegeria that differ in life cycle traits (diapause thresholds and voltinism) along both north-south and east-west clines. Using a de novo-assembled genome, we reconstruct colonization histories and demographic relationships. Based on the inferred population structure, we then scan the genome for candidate loci showing signs of divergent selection potentially associated with population differences in life cycle traits. The identified candidate genes include a number of components of the insect circadian clock (timeless, timeless2, period, cryptochrome and clockwork orange). Most notably, the gene timeless, which has previously been experimentally linked to life cycle regulation in P. aegeria, is here found to contain a novel 97-amino acid deletion unique to, and fixed in, a single population. These results add to a growing body of research framing circadian gene variation as a potential mechanism for generating local adaptation of life cycles.

  Read more about Local adaptation of life cycles in a butterfly is associated with variation in several circadian clock genes

• Extensive transcriptomic profiling of pupal diapause in a butterfly reveals a dynamic phenotype

  2022. Peter Pruisscher (et al.). Molecular Ecology 31 (4), 1269-1280

  Article

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

  Read more about Extensive transcriptomic profiling of pupal diapause in a butterfly reveals a dynamic phenotype

• Thermal performance under constant temperatures can accurately predict insect development times across naturally variable microclimates

  2021. Loke von Schmalensee (et al.). Ecology Letters 24 (8), 1633-1645

  Article

  External conditions can drive biological rates in ectotherms by directly influencing body temperatures. While estimating the temperature dependence of performance traits such as growth and development rate is feasible under controlled laboratory settings, predictions in nature are difficult. One major challenge lies in translating performance under constant conditions to fluctuating environments. Using the butterfly Pieris napi as model system, we show that development rate, an important fitness trait, can be accurately predicted in the field using models parameterized under constant laboratory temperatures. Additionally, using a factorial design, we show that accurate predictions can be made across microhabitats but critically hinge on adequate consideration of non-linearity in reaction norms, spatial heterogeneity in microclimate and temporal variation in temperature. Our empirical results are also supported by a comparison of published and simulated data. Conclusively, our combined results suggest that, discounting direct effects of temperature, insect development rates are generally unaffected by thermal fluctuations.

  Read more about Thermal performance under constant temperatures can accurately predict insect development times across naturally variable microclimates

• Urbanization extends flight phenology and leads to local adaptation of seasonal plasticity in Lepidoptera

  2021. Thomas Merckx (et al.). Proceedings of the National Academy of Sciences of the United States of America 118 (40)

  Article

  Urbanization is gaining force globally, which challenges biodiversity, and it has recently also emerged as an agent of evolutionary change. Seasonal phenology and life cycle regulation are essential processes that urbanization is likely to alter through both the urban heat island effect (UHI) and artificial light at night (ALAN). However, how UHI and ALAN affect the evolution of seasonal adaptations has received little attention. Here, we test for the urban evolution of seasonal life-history plasticity, specifically changes in the photoperiodic induction of diapause in two lepidopterans, Pieris napi (Pieridae) and Chiasmia clathrata (Geometridae). We used long-term data from standardized monitoring and citizen science observation schemes to compare yearly phenological flight curves in six cities in Finland and Sweden to those of adjacent rural populations. This analysis showed for both species that flight seasons are longer and end later in most cities, suggesting a difference in the timing of diapause induction. Then, we used common garden experiments to test whether the evolution of the photoperiodic reaction norm for diapause could explain these phenological changes for a subset of these cities. These experiments demonstrated a genetic shift for both species in urban areas toward a lower daylength threshold for direct development, consistent with predictions based on the UHI but not ALAN. The correspondence of this genetic change to the results of our larger-scale observational analysis of in situ flight phenology indicates that it may be widespread. These findings suggest that seasonal life cycle regulation evolves in urban ectotherms and may contribute to ecoevolutionary dynamics in cities.

  Read more about Urbanization extends flight phenology and leads to local adaptation of seasonal plasticity in Lepidoptera

• Watching the days go by: Asymmetric regulation of caterpillar development by changes in photoperiod

  2021. Olle Lindestad, Inger M. Aalberg Haugen, Karl Gotthard. Ecology and Evolution 11 (10), 5402-5412

  Article

  Many insects possess the plastic ability to either develop directly to adulthood, or enter diapause and postpone reproduction until the next year, depending on environmental cues (primarily photoperiod) that signal the amount of time remaining until the end of the growth season. These two alternative pathways often differ in co-adapted life-history traits, for example, with slower development and larger size in individuals headed for diapause. The developmental timing of these differences may be of adaptive importance: If traits diverge early, the potential for phenotypic differences between the pathways is greater, whereas if traits diverge late, the risk may be lower of expressing a maladaptive phenotype if the selective environment changes during development. Here, we explore the effects of changes in photoperiodic information during life on pupal diapause and associated life-history traits in the butterfly Pararge aegeria. We find that both pupal diapause and larval development rate are asymmetrically regulated: While exposure to long days late in life (regardless of earlier experiences) was sufficient to produce nondiapause development and accelerate larval development accordingly, more prolonged exposure to short days was required to induce diapause and slow down prediapause larval development. While the two developmental pathways diverged early in development, development rates could be partially reversed by altered environmental cues. Meanwhile, pathway differences in body size were more inflexible, despite emerging late in development. These results show how several traits may be shaped by the same environmental cue (photoperiod), but along subtly different ontogenies, into an integrated phenotype.

  Read more about Watching the days go by

• Evolutionary impacts of winter climate change on insects

  2020. Katie Elizabeth Marshall, Karl Gotthard, Caroline Margaret Williams. Current Opinion in Insect Science 41, 54-62

  Article

  Overwintering is a serious challenge for insects, and winters are rapidly changing as climate shifts. The capacity for phenotypic plasticity and evolutionary adaptation will determine which species profit or suffer from these changes. Here we discuss current knowledge on the potential and evidence for evolution in winter-relevant traits among insect species and populations. We conclude that the best evidence for evolutionary shifts in response to changing winters remain those related to changes in phenology, but all evidence points to cold hardiness as also having the potential to evolve in response to climate change. Predicting future population sizes and ranges relies on understanding to what extent evolution in winter-related traits is possible, and remains a serious challenge.

  Read more about Evolutionary impacts of winter climate change on insects

• Variation in butterfly diapause duration in relation to voltinism suggests adaptation to autumn warmth, not winter cold

  2020. Olle Lindestad (et al.). Functional Ecology 34 (5), 1029-1040

  Article

  The life cycles of animals vary in relation to local climate, as a result of both direct environmental effects and population-level variation in plastic responses. Insects often respond to the approach of winter by entering diapause, a hormonally programmed resting state where development is suspended and metabolism suppressed. Populations often differ in the duration of diapause, but the adaptive reasons for this are unclear. We performed a common-garden overwintering experiment with respirometric measurements in order to investigate the progression of diapause in the butterfly Pararge aegeria. Both the duration of diapause and the depth of metabolic suppression were shown to vary between populations. In contrast to previous results from various insects, diapause duration did not correspond to the local length of winter. Instead, the observed pattern was consistent with a scenario in which diapause duration is primarily a product of selection for suppressed metabolism during warm autumn conditions. The relationship between optimal diapause duration and the length of the warm season is complicated by variation in the number of yearly generations (voltinism). These results shed new light on variation in diapause ecophysiology, and highlight voltinism as an integrated product of selection at multiple points in the seasonal cycle. A free Plain Language Summary can be found within the Supporting Information of this article.

  Read more about Variation in butterfly diapause duration in relation to voltinism suggests adaptation to autumn warmth, not winter cold

• Local adaptation of photoperiodic plasticity maintains life cycle variation within latitudes in a butterfly

  2019. Olle Lindestad (et al.). Ecology 100 (1)

  Article

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

  Read more about Local adaptation of photoperiodic plasticity maintains life cycle variation within latitudes in a butterfly

• Butterfly-host plant synchrony determines patterns of host use across years and regions

  2019. Tenna Toftegaard (et al.). Oikos 128 (4), 493-502

  Article

  Variation in the degree of synchrony among host plants and herbivores can disrupt or intensify species interactions, alter the strength of natural selection on traits associated with phenological timing, and drive novel host plant associations. We used field observations from three regions during four seasons to examine how timing of the butterfly herbivore Anthocharis cardamines relative to six host plant species (Arabis hirsuta, Cardamine pratensis, Arabis glabra, Arabidopsis thaliana, Thlaspi caerulescens and Capsella bursa-pastoris) influenced host species use and the choice of host plant individuals within populations. Butterflies laid a larger fraction of their eggs on species that were closer to the butterfly's preferred stage of development than on other host species. Within host plant populations, butterflies showed a stronger preference for individuals with a late phenology when plants within the population were on average more developed at the time of butterfly flight. Our results suggest that changes in synchrony between herbivores and their host plants are associated with changes in both host species use and the choice of host plant individuals differing in phenology within populations. This is likely to be an important mechanism generating variation in interaction intensities and trait selection in the wild, and therefore also relevant for understanding how anthropogenic induced changes, such as global warming, will influence natural communities.

  Read more about Butterfly-host plant synchrony determines patterns of host use across years and regions

• Climate-induced phenology shifts linked to range expansions in species with multiple reproductive cycles per year

  2019. Callum J. Macgregor (et al.). Nature Communications 10

  Article

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

  Read more about Climate-induced phenology shifts linked to range expansions in species with multiple reproductive cycles per year

• Genetic variation underlying local adaptation of diapause induction along a cline in a butterfly

  2018. Peter Pruisscher (et al.). Molecular Ecology 27 (18), 3613-3626

  Article

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

  Read more about Genetic variation underlying local adaptation of diapause induction along a cline in a butterfly

• Sex-linked inheritance of diapause induction in the butterfly Pieris napi

  2017. Peter Pruisscher (et al.). Physiological entomology (Print) 42 (3), 257-265

  Article

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

  Read more about Sex-linked inheritance of diapause induction in the butterfly Pieris napi

• Timing of diapause termination in relation to variation in winter climate

  2017. Philipp Lehmann (et al.). Physiological entomology (Print) 42 (3), 232-238

  Article

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

  Read more about Timing of diapause termination in relation to variation in winter climate

• Winter chilling speeds spring development of temperate butterflies

  2017. Sandra Stålhandske, Karl Gotthard, Olof Leimar. Journal of Animal Ecology 86 (4), 718-729

  Article

  1. Understanding and predicting phenology has become more important with ongoing cli- mate change and has brought about great research efforts in the recent decades. The majority of studies examining spring phenology of insects have focussed on the effects of spring temperatures alone.

  2. Here we use citizen-collected observation data to show that winter cold duration, in addi- tion to spring temperature, can affect the spring emergence of butterflies. Using spatial mixed models, we disentangle the effects of climate variables and reveal impacts of both spring and winter conditions for five butterfly species that overwinter as pupae across the UK, with data from 1976 to 2013 and one butterfly species in Sweden, with data from 2001 to 2013.

  3. Warmer springs lead to earlier emergence in all species and milder winters lead to statisti- cally significant delays in three of the five investigated species. We also find that the delaying effect of winter warmth has become more pronounced in the last decade, during which time winter durations have become shorter.

  4. For one of the studied species, Anthocharis cardamines (orange tip butterfly), we also make use of parameters determined from previous experiments on pupal development to model the spring phenology. Using daily temperatures in the UK and Sweden, we show that recent vari- ation in spring temperature corresponds to 10–15 day changes in emergence time over UK and Sweden, whereas variation in winter duration corresponds to 20 days variation in the south of the UK versus only 3 days in the south of Sweden.

  5. In summary, we show that short winters delay phenology. The effect is most prominent in areas with particularly mild winters, emphasising the importance of winter for the response of ectothermic animals to climate change. With climate change, these effects may become even stronger and apply also at higher latitudes. 

  Read more about Winter chilling speeds spring development of temperate butterflies

• Energy and lipid metabolism during direct and diapause development in a pierid butterfly

  2016. Philipp Lehmann (et al.). Journal of Experimental Biology 219 (19), 3049-3060

  Article

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

  Read more about Energy and lipid metabolism during direct and diapause development in a pierid butterfly

• The developmental race between maturing host plants and their butterfly herbivore – the influence of phenological matching and temperature

  2015. Diana Posledovich (et al.). Journal of Animal Ecology 84 (6), 1690-1699

  Article

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

  Read more about The developmental race between maturing host plants and their butterfly herbivore – the influence of phenological matching and temperature

• Thermal plasticity of growth and development varies adaptively among alternative developmental pathways

  2015. Sami M. Kivelä (et al.). Evolution 69 (9), 2399-2413

  Article

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

  Read more about Thermal plasticity of growth and development varies adaptively among alternative developmental pathways

• The diapause decision as a cascade switch for adaptive developmental plasticity in body mass in a butterfly.

  2010. Karl Gotthard, David Berger. Journal of Evolutionary Biology 23 (6), 1129-37

  Article

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

  Read more about The diapause decision as a cascade switch for adaptive developmental plasticity in body mass in a butterfly.

• What keeps insects small?

  2007. K. Gotthard, D. Berger, R Walters. American naturalist 169, 768-779

  Article

  Read more about What keeps insects small?

Show all publications by Carl Gotthard at Stockholm University