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Erik Svensson

    Erik Svensson

    Organisms inhabiting extreme thermal environments, such as desert birds, have evolved spectacular adaptations to thermoregulate during hot and cold conditions. However, our knowledge of selection for thermoregulation and the potential for... more
    Organisms inhabiting extreme thermal environments, such as desert birds, have evolved spectacular adaptations to thermoregulate during hot and cold conditions. However, our knowledge of selection for thermoregulation and the potential for evolutionary responses is limited, particularly for large organisms experiencing extreme temperature fluctuations. Here we use thermal imaging to quantify selection and genetic variation in thermoregulation in ostriches (Struthio camelus), the world’s largest bird species that is experiencing increasingly volatile temperatures. We found that females who are better at regulating their head temperatures (“thermoregulatory capacity”) had higher egg-laying rates under hotter conditions. Thermoregulatory capacity was both heritable and showed signatures of local adaptation: females originating from more unpredictable climates were better at regulating their head temperatures in response to temperature fluctuations. Together these results reveal that pas...
    Fifteen polymorphic markers were developed from a microsatellite-enriched library for the lizard Podarcis gaigeae. The loci were checked for variability in 68 individuals from a population on the island of Skyros, Greece. The number of... more
    Fifteen polymorphic markers were developed from a microsatellite-enriched library for the lizard Podarcis gaigeae. The loci were checked for variability in 68 individuals from a population on the island of Skyros, Greece. The number of alleles ranged from 3 to 23 per locus and expected heterozygosity from 0.29 and 0.94. Most markers were also polymorphic in three closely related Podarcis species, namely P. erhardi, P. taurica and P. milensis. The markers will be used to examine gene flow and differentiation of island and mainland populations of P. gaigeae.
    Global temperatures are increasing rapidly affecting species globally. Understanding if and how different species can adapt fast enough to keep up with increasing temperatures is of vital importance. One mechanism that can accelerate... more
    Global temperatures are increasing rapidly affecting species globally. Understanding if and how different species can adapt fast enough to keep up with increasing temperatures is of vital importance. One mechanism that can accelerate adaptation and promote evolutionary rescue is sexual selection. Two different mechanisms by which sexual selection can facilitate adaptation are pre- and postcopulatory sexual selection. However, the relative effects of these different forms of sexual selection in promoting adaptation are unknown. Here, we present the results from an experimental study in which we exposed fruit flies Drosophila melanogaster to either no mate choice or 1 of 2 different sexual selection regimes (pre- and postcopulatory sexual selection) for 6 generations, under different thermal regimes. Populations showed evidence of thermal adaptation under precopulatory sexual selection, but this effect was not detected in the postcopulatory sexual selection and the no choice mating re...
    The evolution of sex chromosomes, and patterns of sex-biased gene expression and dosage compensation, are poorly known among early winged insects such as odonates. We assembled and annotated the genome of Ischnura elegans (blue-tailed... more
    The evolution of sex chromosomes, and patterns of sex-biased gene expression and dosage compensation, are poorly known among early winged insects such as odonates. We assembled and annotated the genome of Ischnura elegans (blue-tailed damselfly), which, like other odonates, has a male-hemigametic sex-determining system (X0 males, XX females). By identifying X-linked genes in I. elegans and their orthologs in other insect genomes, we found homologies between the X chromosome in odonates and chromosomes of other orders, including the X chromosome in Coleoptera. Next, we showed balanced expression of X-linked genes between sexes in adult I. elegans, i.e. evidence of dosage compensation. Finally, among the genes in the sex-determining pathway only fruitless was found to be X-linked, while only doublesex showed sex-biased expression. This study reveals partly conserved sex chromosome synteny and independent evolution of dosage compensation among insect orders separated by several hundred million years of evolutionary history.
    Temperature has a crucial influence on the places where species can survive and reproduce. Past research has primarily focused on survival, making it unclear if temperature fluctuations constrain reproductive success, and if so whether... more
    Temperature has a crucial influence on the places where species can survive and reproduce. Past research has primarily focused on survival, making it unclear if temperature fluctuations constrain reproductive success, and if so whether populations harbour the potential to respond to climatic shifts. Here, using two decades of data from a large experimental breeding programme of the iconic ostrich (Struthio camelus) in South Africa, we show that the number of eggs females laid and the number of sperm males produced were highly sensitive to natural temperature extremes (ranging from −5 °C to 45 °C). This resulted in reductions in reproductive success of up to 44% with 5 °C deviations from their thermal optimum. In contrast, gamete quality was largely unaffected by temperature. Extreme temperatures also did not expose trade-offs between gametic traits. Instead, some females appeared to invest more in reproducing at high temperatures, which may facilitate responses to climate change. Th...
    The comment by Myers-Smith and Myers focuses on three main points: (i) the lack of a mechanistic explanation for climate-selection relationships, (ii) the appropriateness of the climate data used in our analysis, and (iii) our focus on... more
    The comment by Myers-Smith and Myers focuses on three main points: (i) the lack of a mechanistic explanation for climate-selection relationships, (ii) the appropriateness of the climate data used in our analysis, and (iii) our focus on estimating climate-selection relationships across (rather than within) taxonomic groups. We address these critiques in our response.
    Although rapid evolution of body size on islands has long been known, the ecological mechanisms behind this island phenomenon remain poorly understood. Diet is an important selective pressure for morphological divergence. Here we... more
    Although rapid evolution of body size on islands has long been known, the ecological mechanisms behind this island phenomenon remain poorly understood. Diet is an important selective pressure for morphological divergence. Here we investigate if selection for novel diets has contributed to the multiple independent cases of island gigantism in the Skyros wall lizard (Podarcis gaigeae) and if diet, predation, or both factors best explain island gigantism. We combined data on body size, shape, bite force, and realized and available diets to address this. Several lines of evidence suggest that diet has contributed to the island gigantism. The larger islet lizards have relatively wider heads and higher bite performance in relation to mainland lizards than would be expected from size differences alone. The proportions of consumed and available hard prey are higher on islets than mainland localities, and lizard body size is significantly correlated with the proportion of hard prey. Furtherm...
    dynamics and population biology of a polymorphic insect
    Sexually antagonistic (SA) genetic variation—in which genotypes favoured in one sex are disfavoured in the other—is predicted to be common and has been documented in several animal and plant populations, yet we currently know little about... more
    Sexually antagonistic (SA) genetic variation—in which genotypes favoured in one sex are disfavoured in the other—is predicted to be common and has been documented in several animal and plant populations, yet we currently know little about its pervasiveness among species or its population genetic basis. Recent applications of genomics in studies of SA genetic variation have highlighted considerable methodological challenges to the identification and characterisation of SA genes, raising questions about the feasibility of genomic approaches for inferring SA selection. The related fields of local adaptation and statistical genomics have previously dealt with similar challenges, and lessons from these disciplines can therefore help overcome current difficulties in applying genomics to study SA genetic variation. Here, we integrate theoretical and analytical concepts from local adaptation and statistical genomics research—including FST and FIS statistics, genome-wide association studies ...
    Insect distributions are shifting rapidly in response to climate change and are undergoing rapid evolutionary change. We investigate the molecular signatures underlying local adaptation in the range-expanding damselfly, Ischnura elegans.... more
    Insect distributions are shifting rapidly in response to climate change and are undergoing rapid evolutionary change. We investigate the molecular signatures underlying local adaptation in the range-expanding damselfly, Ischnura elegans. Using a landscape genomic approach combined with generalized dissimilarity modelling (GDM), we detect selection signatures on loci via allelic frequency change along environmental gradients. We analyse 13,612 Single Nucleotide Polymorphisms (SNPs), derived from Restriction site-Associated DNA sequencing (RADseq), in 426 individuals from 25 sites spanning the I. elegans distribution in Sweden, including its expanding northern range edge. Environmental association analysis (EAA) and the magnitude of allele frequency change along the range expansion gradient revealed significant signatures of selection in relation to high maximum summer temperature, high mean annual precipitation, and low wind speeds at the range edge. SNP annotations with significant ...
    Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary... more
    Climate change has the potential to affect the ecology and evolution of every species on Earth. Although the ecological consequences of climate change are increasingly well documented, the effects of climate on the key evolutionary process driving adaptation-natural selection-are largely unknown. We report that aspects of precipitation and potential evapotranspiration, along with the North Atlantic Oscillation, predicted variation in selection across plant and animal populations throughout many terrestrial biomes, whereas temperature explained little variation. By showing that selection was influenced by climate variation, our results indicate that climate change may cause widespread alterations in selection regimes, potentially shifting evolutionary trajectories at a global scale.
    Humans have dramatic, diverse and far-reaching influences on the evolution of other organisms. Numerous examples of this human-induced contemporary evolution have been reported in a number of ‘contexts’, including hunting, harvesting,... more
    Humans have dramatic, diverse and far-reaching influences on the evolution of other organisms. Numerous examples of this human-induced contemporary evolution have been reported in a number of ‘contexts’, including hunting, harvesting, fishing, agriculture, medicine, climate change, pollution, eutrophication, urbanization, habitat fragmentation, biological invasions and emerging/disappearing diseases. Although numerous papers, journal special issues and books have addressed each of these contexts individually, the time has come to consider them together and thereby seek important similarities and differences. The goal of this special issue, and this introductory paper, is to promote and expand this nascent integration. We first develop predictions as to which human contexts might cause the strongest and most consistent directional selection, the greatest changes in evolutionary potential, the greatest genetic (as opposed to plastic) changes and the greatest effects on evolutionary di...
    The role of mutations have been subject to many controversies since the formation of the Modern Synthesis of evolution in the early 1940ties. Geneticists in the early half of the twentieth century tended to view mutations as a limiting... more
    The role of mutations have been subject to many controversies since the formation of the Modern Synthesis of evolution in the early 1940ties. Geneticists in the early half of the twentieth century tended to view mutations as a limiting factor in evolutionary change. In contrast, natural selection was largely viewed as a “sieve” whose main role was to sort out the unfit but which could not create anything novel alone. This view gradually changed with the development of mathematical population genetics theory, increased appreciation of standing genetic variation and the discovery of more complex forms of selection, including balancing selection. Short-term evolutionary responses to selection are mainly influenced by standing genetic variation, and are predictable to some degree using information about the genetic variance–covariance matrix (G) and the strength and form of selection (e. g. the vector of selection gradients, β). However, predicting long-term evolution is more challengin...
    In seasonally-variable environments, phenotypic plasticity in phenology may be critical for adaptation to fluctuating environmental (temperature) conditions. Using an 18-generation longitudinal dataset from natural insect (damselfly)... more
    In seasonally-variable environments, phenotypic plasticity in phenology may be critical for adaptation to fluctuating environmental (temperature) conditions. Using an 18-generation longitudinal dataset from natural insect (damselfly) populations, we show that phenology has strongly advanced. Individual fitness data suggest this is likely an adaptive response towards a thermally-dependent fitness optimum. A laboratory experiment revealed that developmental plasticity qualitatively matches environmental-dependence of selection, partially explaining observed phenological advance. Expanding our analysis to the macroevolutionary level, we use a database of over 1-million occurrence records and spatiotemporally-matched temperature data from 49 Swedish Odonate species to infer macroevolutionary dynamics of phenology. Phenological plasticity was more closely aligned with adaptation for species that have recently colonized northern latitudes, with more phenological mismatch at lower latitude...
    The last decades have seen frequent calls for a more extended evolutionary synthesis (EES) that will supposedly overcome the limitations in the current evolutionary framework with its intellectual roots in the Modern Synthesis (MS). Some... more
    The last decades have seen frequent calls for a more extended evolutionary synthesis (EES) that will supposedly overcome the limitations in the current evolutionary framework with its intellectual roots in the Modern Synthesis (MS). Some radical critics even want to entirely abandon the current evolutionary framework, claiming that the MS (often erroneously labelled “Neo-Darwinism”) is outdated, and will soon be replaced by an entirely new framework, such as the Third Way of Evolution (TWE). Such criticisms are not new, but have repeatedly re-surfaced every decade since the formation of the MS, and they were particularly articulated by developmental biologist Conrad Waddington and paleontologist Stephen Jay Gould. Waddington, Gould and later critics argued that the MS was too narrowly focused on genes and natural selection, and that it ignored developmental processes, epigenetics, paleontology and macroevolutionary phenomena. More recent critics partly recycle these old arguments an...
    Local adaptation is of fundamental interest to evolutionary biologists. Traditionally, local adaptation has been studied using reciprocal transplant experiments to quantify fitness differences between residents and immigrants in pairwise... more
    Local adaptation is of fundamental interest to evolutionary biologists. Traditionally, local adaptation has been studied using reciprocal transplant experiments to quantify fitness differences between residents and immigrants in pairwise transplants between study populations. Previous studies have detected local adaptation in some cases, but others have shown lack of adaptation or even maladaptation. Recently, the importance of different fitness components, such as survival and fecundity, to local adaptation have been emphasized. Here, we address another neglected aspect in studies of local adaptation: sex differences. Given the ubiquity of sexual dimorphism in life histories and phenotypic traits, this neglect is surprising, but may be partly explained by differences in research traditions and terminology in the fields of local adaptation and sexual selection. Studies that investigate differences in mating success between resident and immigrants across populations tend to be framed...
    Mechanistic and experimental analysis of condition and reproduction in a polymorphic lizard
    Background Evolutionary processes can cause strong spatial genetic signatures, such as local loss of genetic diversity, or conflicting histories from mitochondrial versus nuclear markers. Investigating these genetic patterns is important,... more
    Background Evolutionary processes can cause strong spatial genetic signatures, such as local loss of genetic diversity, or conflicting histories from mitochondrial versus nuclear markers. Investigating these genetic patterns is important, as they may reveal obscured processes and players. The maternally inherited bacterium Wolbachia is among the most widespread symbionts in insects. Wolbachia typically spreads within host species by conferring direct fitness benefits, and/or by manipulating its host reproduction to favour infected over uninfected females. Under sufficient selective advantage, the mitochondrial haplotype associated with the favoured maternally-inherited symbiotic strains will spread (i.e. hitchhike), resulting in low mitochondrial genetic variation across the host species range. Method The common bluetail damselfly (Ischnura elegans: van der Linden, 1820) has recently emerged as a model organism for genetics and genomic signatures of range expansion during climate ch...
    Colour polymorphisms are popular study systems among biologists interested in evolutionary dynamics, genomics, sexual selection and sexual conflict. In many damselfly groups, such as in the globally distributed genus Ischnura (forktails),... more
    Colour polymorphisms are popular study systems among biologists interested in evolutionary dynamics, genomics, sexual selection and sexual conflict. In many damselfly groups, such as in the globally distributed genus Ischnura (forktails), sex-limited female colour polymorphisms occur in multiple species. Female-polymorphic species contain two or three female morphs, one of which phenotypically matches the male (androchrome or male mimic) and the other(s) which are phenotypically distinct from the male (heterochrome). These female colour polymorphisms are thought to be maintained by frequency-dependent sexual conflict, but their macroevolutionary histories are unknown, due to the lack of a robust molecular phylogeny. Here, we present the first time-calibrated phylogeny of Ischnura, using a multispecies coalescent approach (StarBEAST2) and incorporating both molecular and fossil data for 41 extant species (55% of the genus). We estimate the age of Ischnura to be between 13.8 and 23.4 millions of years, i.e. Miocene. We infer the ancestral state of this genus as female monomorphism with heterochrome females, with multiple gains and losses of female polymorphisms, evidence of trans-species female polymorphisms and a significant positive relationship between female polymorphism incidence and current geographic range size. Our study provides a robust phylogenetic framework for future research on the dynamic macroevolutionary history of this clade with its extraordinary diversity of sex-limited female polymorphisms.
    Pleiotropy (multiple phenotypic effects of single genes) and epistasis (gene interaction) have key roles in the development of complex phenotypes, especially in polymorphic taxa. The development of discrete and heritable phenotypic... more
    Pleiotropy (multiple phenotypic effects of single genes) and epistasis (gene interaction) have key roles in the development of complex phenotypes, especially in polymorphic taxa. The development of discrete and heritable phenotypic polymorphisms often emerges from major-effect genes that interact with other loci and have pleiotropic effects on multiple traits. We quantified gene expression changes during ontogenetic colour development in a polymorphic insect (damselfly:Ischnura elegans), with three heritable female morphs, one being a male mimic. This female colour polymorphism is maintained by male mating harassment and sexual conflict. Using transcriptome sequencing andde novoassembly, we demonstrate that all three morphs downregulate gene expression during early colour development. The morphs become increasingly differentiated during sexual maturation and when developing adult colouration. These different ontogenetic trajectories arise because the male-mimic shows accelerated (he...
    To understand host–parasite interactions, it is necessary to quantify variation and covariation in defence traits. We quantified parasite resistance and fitness tolerance of a polymorphic damselfly ( Ischnura elegans ), an insect with... more
    To understand host–parasite interactions, it is necessary to quantify variation and covariation in defence traits. We quantified parasite resistance and fitness tolerance of a polymorphic damselfly ( Ischnura elegans ), an insect with three discrete female colour morphs but with monomorphic males. We quantified sex and morph differences in parasite resistance (prevalence and intensity of water mite infections) and morph-specific fitness tolerance in the females in natural populations for over a decade. There was no evidence for higher parasite susceptibility in males as a cost of sexual selection, whereas differences in defence mechanisms between female morphs are consistent with correlational selection operating on combinations of parasite resistance and tolerance. We suggest that tolerance differences between female morphs interact with frequency-dependent sexual conflict, which maintains the polymorphism locally. Host–parasite interactions can therefore shape intra- and intersexu...
    Odonata (dragonflies and damselflies) present an unparalleled insect model to integrate evolutionary genomics with ecology for the study of insect evolution. Key features of Odonata include their ancient phylogenetic position, extensive... more
    Odonata (dragonflies and damselflies) present an unparalleled insect model to integrate evolutionary genomics with ecology for the study of insect evolution. Key features of Odonata include their ancient phylogenetic position, extensive phenotypic and ecological diversity, several unique evolutionary innovations, ease of study in the wild and usefulness as bioindicators for freshwater ecosystems worldwide. In this review, we synthesize studies on the evolution, ecology and physiology of odonates, highlighting those areas where the integration of ecology with genomics would yield significant insights into the evolutionary processes that would not be gained easily by working on other animal groups. We argue that the unique features of this group combined with their complex life cycle, flight behaviour, diversity in ecological niches and their sensitivity to anthropogenic change make odonates a promising and fruitful taxon for genomics focused research. Future areas of research that de...
    Climate change affects organisms worldwide with profound ecological and evolutionary consequences, often increasing population extinction risk. Climatic factors can increase the strength, variability, or direction of natural selection on... more
    Climate change affects organisms worldwide with profound ecological and evolutionary consequences, often increasing population extinction risk. Climatic factors can increase the strength, variability, or direction of natural selection on phenotypic traits, potentially driving adaptive evolution. Phenotypic plasticity in relation to temperature can allow organisms to maintain fitness in response to increasing temperatures, thereby “buying time” for subsequent genetic adaptation and promoting evolutionary rescue. Although many studies have shown that organisms respond plastically to increasing temperatures, it is unclear if such thermal plasticity is adaptive. Moreover, we know little about how natural and sexual selection operate on thermal reaction norms, reflecting such plasticity. Here, we investigate how natural and sexual selection shape phenotypic plasticity in two congeneric and phenotypically similar sympatric insect species. We show that the thermal optima for longevity and ...
    Assortative mating is of interest because of its role in speciation and the maintenance of species boundaries. However, we know little about how within-species assortment is related to interspecific sexual isolation. Most previous studies... more
    Assortative mating is of interest because of its role in speciation and the maintenance of species boundaries. However, we know little about how within-species assortment is related to interspecific sexual isolation. Most previous studies of assortative mating have focused on a single trait in males and females, rather than utilizing multivariate trait information. Here we investigate how intraspecific assortative mating relates to sexual isolation in two sympatric and congeneric damselfly species (genus Calopteryx). We connect intraspecific assortment to interspecific sexual isolation by combining field observations, mate preference experiments and enforced copulation experiments. Using canonical correlation analysis, we demonstrate multivariate intraspecific assortment for body size and body shape. Males of the smaller species mate more frequently with heterospecific females than males of the larger species, which showed less attraction to small heterospecific females. Field exper...
    ABSTRACT Differences in ecological conditions can result in the evolution of dramatic inter-population shifts in whole suites of traits. We studied variation in reproductive output in three lizard populations of the Skyros Wall Lizard... more
    ABSTRACT Differences in ecological conditions can result in the evolution of dramatic inter-population shifts in whole suites of traits. We studied variation in reproductive output in three lizard populations of the Skyros Wall Lizard {Podareis galgeae, Lacertidae) endemic to the Skyros Archipelago (Greece), which live under similar climatic conditions but differ in prédation pressure and food availability. Based on the island syndrome" hypothesis, we predicted that females from island populations would produce larger, but fewer offspring. The study populations differ conspicuously in average body size, with males from the satellite Lakonissi and Diavates islets being respectively 20% and 39% larger than males from the main Skyros Island. Lizards from these predator-free islets produced eggs of larger size than the main Skyros population; however, they also produced significantly larger clutches than the Skyros population (2.31 ± 0.83 and 2.73 ± 1.0 vs. 1.97 ± 0.58 eggs). All inter-population differences in clutch size, clutch volume, and egg size were explained by corresponding differences in average body size of the dams, revealing that across all populations, reproductive effort scaled similarly with maternal body size. There was no evidence of trade-offs between egg size and clutch size as generally encountered in many reptile taxa. The occurrence of this unusual pattern of reproductive investment among islet populations of giants is probably best explained by the occurrence of two underlying drivers: first, the substantial marine subsidies by resident seabird colonies and second, the existence of intense cannibalistic behaviors in the form of attacks to the tail and severe intraspecific predation on juveniles. This suggests that subsidies-driven gigantism in island endemics may free species from such trade-offs and allow a population to maximize reproductive output in multiple, normally conflicting dimensions.
    We present The Odonate Phenotypic Database (OPD): an online data resource of dragonfly and damselfly phenotypes (Insecta: Odonata). Odonata is a relatively small insect order that currently consists of about 6400 species belonging to 32... more
    We present The Odonate Phenotypic Database (OPD): an online data resource of dragonfly and damselfly phenotypes (Insecta: Odonata). Odonata is a relatively small insect order that currently consists of about 6400 species belonging to 32 families. The database consists of multiple morphological, life-history and behavioral traits, and biogeographical information collected from literature sources. We see taxon-specific phenotypic databases from Odonata and other organismal groups as becoming an increasing valuable resource in comparative studies. Our database has phenotypic records for 1011 of all 6400 known odonate species. The database is accessible at http://www.odonatephenotypicdatabase.org/, and a static version with an information file about the variables in the database is archived at Dryad.
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