Mating success at high temperature in highland‐ and lowland‐derived populations as well as in heat knock‐down selected Drosophila buzzatii

Thermal‐stress selection can affect multiple fitness components including mating success. Reproductive success is one of the most inclusive measures of overall fitness, and mating success is a major component of reproduction. However, almost no attention has been spent to test how mating success can be affected by thermal‐stress selection. In this study, we examine the mating success in the cactophilic Drosophila buzzatii Patterson & Wheeler (Diptera: Drosophilidae) derived from two natural populations that nearly represent the ends of an altitudinal cline for heat knock‐down resistance. Furthermore, we extended the analysis using laboratory lines artificially selected for high and low heat knock‐down resistance. Mating success at high temperature was found to be higher in the lowland than the highland population after a heat pre‐treatment. Moreover, individuals selected for heat knock‐down resistance showed higher mating success at high temperature than did individuals selected for low knock‐down resistance. These results indicate that adaptation to thermal stress can confer an advantage on fitness‐related traits including mating success and highlight the benefits of earlier heat exposure as an adaptive plastic response affecting mating success under stress of higher temperature.     

Heat tolerance in Drosophila subobscura along a latitudinal gradient: Contrasting patterns between plastic and genetic responses

Susceptibility to global warming relies on how thermal tolerances respond to increasing temperatures through plasticity or evolution. Climatic adaptation can be assessed by examining the geographic variation in thermal‐related traits. We studied latitudinal patterns in heat tolerance in Drosophila subobscura reared at two temperatures. We used four static stressful temperatures to estimate the thermal death time (TDT) curves, and two ramping assays with fast and slow heating rates. Thermal death time curves allow estimation of the critical thermal maximum (CT_max), by extrapolating to the temperature that would knock down the flies almost “instantaneously,” and the thermal sensitivity to increasing stressful temperatures. We found a positive latitudinal cline for CT_max, but no clinal pattern for knockdown temperatures estimated from the ramping assays. Although high‐latitude populations were more tolerant to an acute heat stress, they were also more sensitive to prolonged exposure to less stressful temperatures, supporting a trade‐off between acute and chronic heat tolerances. Conversely, developmental plasticity did not affect CT_max but increased the tolerance to chronic heat exposition. The patterns observed from the TDT curves help to understand why the relationship between heat tolerance and latitude depends on the methodology used and, therefore, these curves provide a more complete and reliable measurement of heat tolerance.     

The genomic footprint of climate adaptation in Chironomus riparius

The gradual heterogeneity of climatic factors poses varying selection pressures across geographic distances that leave signatures of clinal variation in the genome. Separating signatures of clinal adaptation from signatures of other evolutionary forces, such as demographic processes, genetic drift and adaptation, to nonclinal conditions of the immediate local environment is a major challenge. Here, we examine climate adaptation in five natural populations of the harlequin fly Chironomus riparius sampled along a climatic gradient across Europe. Our study integrates experimental data, individual genome resequencing, Pool‐Seq data and population genetic modelling. Common‐garden experiments revealed significantly different population growth rates at test temperatures corresponding to the population origin along the climate gradient, suggesting thermal adaptation on the phenotypic level. Based on a population genomic analysis, we derived empirical estimates of historical demography and migration. We used an F_ST outlier approach to infer positive selection across the climate gradient, in combination with an environmental association analysis. In total, we identified 162 candidate genes as genomic basis of climate adaptation. Enriched functions among these candidate genes involved the apoptotic process and molecular response to heat, as well as functions identified in studies of climate adaptation in other insects. Our results show that local climate conditions impose strong selection pressures and lead to genomic adaptation despite strong gene flow. Moreover, these results imply that selection to different climatic conditions seems to converge on a functional level, at least between different insect species.     

A Drosophila laboratory evolution experiment points to low evolutionary potential under increased temperatures likely to be experienced in the future

The ability to respond evolutionarily to increasing temperatures is important for survival of ectotherms in a changing climate. Recent studies suggest that upper thermal limits may be evolutionary constrained. We address this hypothesis in a laboratory evolution experiment, encompassing ecologically relevant thermal regimes. To examine the potential for species to respond to climate change, we exposed replicate populations of Drosophila melanogaster to increasing temperatures (0.3 °C every generation) for 20 generations, whereas corresponding replicate control populations were held at benign thermal conditions throughout the experiment. We hypothesized that replicate populations exposed to increasing temperatures would show increased resistance to warm and dry environments compared with replicate control populations. Contrasting replicate populations held at the two thermal regimes showed (i) an increase in desiccation resistance and a decline in heat knock‐down resistance in replicate populations exposed to increasing temperatures, (ii) similar egg‐to‐adult viability and fecundity in replicate populations from the two thermal regimes, when assessed at high stressful temperatures and (iii) no difference in nucleotide diversity between thermal regimes. The limited scope for adaptive evolutionary responses shown in this study highlights the challenges faced by ectotherms under climate change.     

Geographic clines in wing morphology relate to colonization history in New World but not Old World populations of yellow dung flies

Geographic clines offer insights about putative targets and agents of natural selection as well as tempo and mode of adaptation. However, demographic processes can lead to clines that are indistinguishable from adaptive divergence. Using the widespread yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae), we examine quantitative genetic differentiation (Q_ST) of wing shape across North America, Europe, and Japan, and compare this differentiation with that of ten microsatellites (F_ST). Morphometric analyses of 28 populations reared at three temperatures revealed significant thermal plasticity, sexual dimorphism, and geographic differentiation in wing shape. In North America morphological differentiation followed the decline in microsatellite variability along the presumed route of recent colonization from the southeast to the northwest. Across Europe, where S. stercoraria presumably existed for much longer time and where no molecular pattern of isolation by distance was evident, clinal variation was less pronounced despite significant morphological differentiation (Q_ST>F_ST). Shape vector comparisons further indicate that thermal plasticity (hot‐to‐cold) does not mirror patterns of latitudinal divergence (south‐to‐north), as might have been expected under a scenario with temperature as the major agent of selection. Our findings illustrate the importance of detailed phylogeographic information when interpreting geographic clines of dispersal traits in an adaptive evolutionary framework.     

Signatures of diversifying selection at EST‐SSR loci and association with climate in natural Eucalyptus populations

Understanding the environmental parameters that drive adaptation among populations is important in predicting how species may respond to global climatic changes and how gene pools might be managed to conserve adaptive genetic diversity. Here, we used Bayesian F_ST outlier tests and allele–climate association analyses to reveal two Eucalyptus EST‐SSR loci as strong candidates for diversifying selection in natural populations of a southwestern Australian forest tree, Eucalyptus gomphocephala (Myrtaceae). The Eucalyptus homolog of a CONSTANS‐like gene was an F_ST outlier, and allelic variation showed significant latitudinal clinal associations with annual and winter solar radiation, potential evaporation, summer precipitation and aridity. A second F_ST outlier locus, homologous to quinone oxidoreductase, was significantly associated with measures of temperature range, high summer temperature and summer solar radiation, with important implications for predicting the effect of temperature on natural populations in the context of climate change. We complemented these data with investigations into neutral population genetic structure and diversity throughout the species range. This study provides an investigation into selection signatures at gene‐homologous EST‐SSRs in natural Eucalyptus populations, and contributes to our understanding of the relationship between climate and adaptive genetic variation, informing the conservation of both putatively neutral and adaptive components of genetic diversity.     

Secondary contact and local adaptation contribute to genome‐wide patterns of clinal variation in Drosophila melanogaster

Populations arrayed along broad latitudinal gradients often show patterns of clinal variation in phenotype and genotype. Such population differentiation can be generated and maintained by both historical demographic events and local adaptation. These evolutionary forces are not mutually exclusive and can in some cases produce nearly identical patterns of genetic differentiation among populations. Here, we investigate the evolutionary forces that generated and maintain clinal variation genome‐wide among populations of Drosophila melanogaster sampled in North America and Australia. We contrast patterns of clinal variation in these continents with patterns of differentiation among ancestral European and African populations. Using established and novel methods we derive here, we show that recently derived North America and Australia populations were likely founded by both European and African lineages and that this hybridization event likely contributed to genome‐wide patterns of parallel clinal variation between continents. The pervasive effects of admixture mean that differentiation at only several hundred loci can be attributed to the operation of spatially varying selection using an F_ST outlier approach. Our results provide novel insight into the well‐studied system of clinal differentiation in D. melanogaster and provide a context for future studies seeking to identify loci contributing to local adaptation in a wide variety of organisms, including other invasive species as well as temperate endemics.     

The quantitative genetic basis of clinal divergence in phenotypic plasticity

Phenotypic plasticity is thought to be an important mechanism for adapting to environmental heterogeneity. Nonetheless, the genetic basis of plasticity is still not well understood. In Drosophila melanogaster and D. simulans, body size and thermal stress resistance show clinal patterns along the east coast of Australia, and exhibit plastic responses to different developmental temperatures. The genetic basis of thermal plasticity, and whether the genetic effects underlying clinal variation in traits and their plasticity are similar, remains unknown. Here, we use line‐cross analyses between a tropical and temperate population of Drosophila melanogaster and D. simulans developed at three constant temperatures (18°C, 25°C, and 29°C) to investigate the quantitative genetic basis of clinal divergence in mean thermal response (elevation) and plasticity (slope and curvature) for thermal stress and body size traits. Generally, the genetic effects underlying divergence in mean response and plasticity differed, suggesting that different genetic models may be required to understand the evolution of trait means and plasticity. Furthermore, our results suggest that nonadditive genetic effects, in particular epistasis, may commonly underlie plastic responses, indicating that current models that ignore epistasis may be insufficient to understand and predict evolutionary responses to environmental change.     

Post‐glacial colonization routes coincide with a life‐history breakpoint along a latitudinal gradient

Although adaptive divergence along environmental gradients has repeatedly been demonstrated, the role of post‐glacial colonization routes in determining phenotypic variation along gradients has received little attention. Here, we used a hierarchical Q_ST–F_ST approach to separate the roles of adaptive and neutral processes in shaping phenotypic variation in moor frog (Rana arvalis) larval life histories along a 1,700 km latitudinal gradient across northern Europe. This species has colonized Scandinavia via two routes with a contact zone in northern Sweden. By using neutral SNP and common garden phenotypic data from 13 populations at two temperatures, we showed that most of the variation along the gradient occurred between the two colonizing lineages. We found little phenotypic divergence within the lineages; however, all phenotypic traits were strongly diverged between the southern and northern colonization routes, with higher growth and development rates and larger body size in the north. The Q_ST estimates between the colonization routes were four times higher than F_ST, indicating a prominent role for natural selection. Q_ST within the colonization routes did not generally differ from F_ST, but we found temperature‐dependent adaptive divergence close to the contact zone. These results indicate that lineage‐specific variation can account for much of the adaptive divergence along a latitudinal gradient.     

Natural selection and neutral evolutionary processes contribute to genetic divergence in leaf traits across a precipitation gradient in the tropical oak Quercus oleoides

The impacts of drought are expanding worldwide as a consequence of climate change. However, there is still little knowledge of how species respond to long‐term selection in seasonally dry ecosystems. In this study, we used Q_ST‐F_ST comparisons to investigate (i) the role of natural selection on population genetic differentiation for a set of functional traits related to drought resistance in the seasonally dry tropical oak Quercus oleoides and (ii) the influence of water availability at the site of population origin and in experimental treatments on patterns of trait divergence. We conducted a thorough phenotypic characterization of 1912 seedlings from ten populations growing in field and greenhouse common gardens under replicated watering treatments. We also genotyped 218 individuals from the same set of populations using eleven nuclear microsatellites. Q_ST distributions for leaf lamina area, specific leaf area, leaf thickness and stomatal pore index were higher than F_ST distribution. Results were consistent across growth environments. Genetic differentiation among populations for these functional traits was associated with the index of moisture at the origin of the populations. Together, our results suggest that drought is an important selective agent for Q. oleoides and that differences in length and severity of the dry season have driven the evolution of genetic differences in functional traits.     

Negative frequency‐dependent selection maintains coexisting genotypes during fluctuating selection

Natural environments are rarely static; rather selection can fluctuate on timescales ranging from hours to centuries. However, it is unclear how adaptation to fluctuating environments differs from adaptation to constant environments at the genetic level. For bacteria, one key axis of environmental variation is selection for planktonic or biofilm modes of growth. We conducted an evolution experiment with Burkholderia cenocepacia, comparing the evolutionary dynamics of populations evolving under constant selection for either biofilm formation or planktonic growth with populations in which selection fluctuated between the two environments on a weekly basis. Populations evolved in the fluctuating environment shared many of the same genetic targets of selection as those evolved in constant biofilm selection, but were genetically distinct from the constant planktonic populations. In the fluctuating environment, mutations in the biofilm‐regulating genes wspA and rpfR rose to high frequency in all replicate populations. A mutation in wspA first rose rapidly and nearly fixed during the initial biofilm phase but was subsequently displaced by a collection of rpfR mutants upon the shift to the planktonic phase. The wspA and rpfR genotypes coexisted via negative frequency‐dependent selection around an equilibrium frequency that shifted between the environments. The maintenance of coexisting genotypes in the fluctuating environment was unexpected. Under temporally fluctuating environments, coexistence of two genotypes is only predicted under a narrow range of conditions, but the frequency‐dependent interactions we observed provide a mechanism that can increase the likelihood of coexistence in fluctuating environments.     

Epigenetic variation reflects dynamic habitat conditions in a rare floodplain herb

Variation of DNA methylation is thought to play an important role for rapid adjustments of plant populations to dynamic environmental conditions, thus compensating for the relatively slow response time of genetic adaptations. However, genetic and epigenetic variation of wild plant populations has not yet been directly compared in fast changing environments. Here, we surveyed populations of Viola elatior from two adjacent habitat types along a successional gradient characterized by strong differences in light availability. Using amplified fragment length polymorphisms (AFLP) and methylation‐sensitive amplification polymorphisms (MSAP) analyses, we found relatively low levels of genetic (H′_gen = 0.19) and epigenetic (H′_epi = 0.23) diversity and high genetic (?_ST = 0.72) and epigenetic (?_ST = 0.51) population differentiation. Diversity and differentiation were significantly correlated, suggesting that epigenetic variation partly depends on the same driving forces as genetic variation. Correlation‐based genome scans detected comparable levels of genetic (17.0%) and epigenetic (14.2%) outlier markers associated with site specific light availability. However, as revealed by separate differentiation‐based genome scans for AFLP, only few genetic markers seemed to be actually under positive selection (0–4.5%). Moreover, principal coordinates analyses and Mantel tests showed that overall epigenetic variation was more closely related to habitat conditions, indicating that environmentally induced methylation changes may lead to convergence of populations experiencing similar habitat conditions and thus may play a major role for the transient and/or heritable adjustment to changing environments. Additionally, using a new MSAP‐scoring approach, we found that mainly the unmethylated (?_ST = 0.60) and CG‐methylated states (?_ST = 0.46) of epiloci contributed to population differentiation and putative habitat‐related adaptation, whereas CHG‐hemimethylated states (?_ST = 0.21) only played a marginal role.     

Parasite‐mediated selection in a natural metapopulation of Daphnia magna

Parasite‐mediated selection varying across time and space in metapopulations is expected to result in host local adaptation and the maintenance of genetic diversity in disease‐related traits. However, nonadaptive processes like migration and extinction‐(re)colonization dynamics might interfere with adaptive evolution. Understanding how adaptive and nonadaptive processes interact to shape genetic variability in life‐history and disease‐related traits can provide important insights into their evolution in subdivided populations. Here we investigate signatures of spatially fluctuating, parasite‐mediated selection in a natural metapopulation of Daphnia magna. Host genotypes from infected and uninfected populations were genotyped at microsatellite markers, and phenotyped for life‐history and disease traits in common garden experiments. Combining phenotypic and genotypic data a Q_ST–F_ST‐like analysis was conducted to test for signatures of parasite mediated selection. We observed high variation within and among populations for phenotypic traits, but neither an indication of host local adaptation nor a cost of resistance. Infected populations have a higher gene diversity (Hs) than uninfected populations and Hs is strongly positively correlated with fitness. These results suggest a strong parasite effect on reducing population level inbreeding. We discuss how stochastic processes related to frequent extinction‐(re)colonization dynamics as well as host and parasite migration impede the evolution of resistance in the infected populations. We suggest that the genetic and phenotypic patterns of variation are a product of dynamic changes in the host gene pool caused by the interaction of colonization bottlenecks, inbreeding, immigration, hybrid vigor, rare host genotype advantage and parasitism. Our study highlights the effect of the parasite in ameliorating the negative fitness consequences caused by the high drift load in this metapopulation.     

Footprints of selection in wild populations of Bicyclus anynana along a latitudinal cline

One of the major questions in ecology and evolutionary biology is how variation in the genome enables species to adapt to divergent environments. Here, we study footprints of thermal selection in candidate genes in six wild populations of the afrotropical butterfly Bicyclus anynana sampled along a c. 3000 km latitudinal cline. We sequenced coding regions of 31 selected genes with known functions in metabolism, pigment production, development and heat shock responses. These include genes for which we expect a priori a role in thermal adaptation and, thus, varying selection pressures along a latitudinal cline, and genes we do not expect to vary clinally and can be used as controls. We identified amino acid substitution polymorphisms in 13 genes and tested these for clinal variation by correlation analysis of allele frequencies with latitude. In addition, we used two F_ST‐based outlier methods to identify loci with higher population differentiation than expected under neutral evolution, while accounting for potentially confounding effects of population structure and demographic history. Two metabolic enzymes of the glycolytic pathway, UGP and Treh, showed clinal variation. The same loci showed elevated population differentiation and were identified as significant outliers. We found no evidence of clines in the pigmentation genes, heat shock proteins and developmental genes. However, we identified outlier loci in more localized parts of the range in the pigmentation genes yellow and black. We discuss that the observed clinal variation and elevated population divergence in UGP and Treh may reflect adaptation to a geographic thermal gradient.     

Separating Effects of Gene Flow and Natural Selection along an Environmental Gradient

Genetic differentiation along environmental clines is often observed as a result of interplay between gene flow and natural selection. In order to understand the relative roles of these processes in shaping this differentiation, we designed a study in which we used two approaches that have not previously been combined, the Q _ST–F _ST comparison and crossbreeding. We examined (1) interpopulation phenotypic and genetic (AFLP) variation, and (2) performance of interpopulation hybrids in a common annual Senecio glaucus. Fitness of interpopulation hybrids (F1 and F2) was tested under simulated population natural conditions in terms of aridity and analyzed for a relationship with (1) spatial distance and (2) environmental differences (amount of annual rainfall). While phenotypic variation corresponded to the clinal changes in aridity along population locations, viz. narrower and longer leaves, longer leaf outgrowths and advanced flowering in more arid environments, the F _ST < 0.1 calculated from AFLP data suggested intensive interpopulation gene flow, with little if any contribution of genetic drift. Performance of hybrids in simulated natural environments revealed heterosis in F1, but a hybrid breakdown in F2 generation. These effects were related to both the spatial distance between hybrid parents and their population rainfall differences. The detected clinal phenotypic variation and outbreeding depression in F2 strongly support presence of aridity-induced clinal natural selection, which is matched by the observed Q _ST ≫ F _ST. From this we conclude that Q _ST–F _ST comparison can detect effect of diversifying selection when patterns of phenotypic variation across sampled locations can be reliably predicted from environmental variation.     

Evolvability of between‐year seed dormancy in populations along an aridity gradient

Under global climate change, adaptation to new conditions is crucial for plant species persistence. This requires the ability to evolve in traits that are correlated with changing climatic variables. We studied between‐year seed dormancy, which correlates with environmental variability, and tested for clinal trends in its evolvability along an aridity gradient in Israel. We conducted a germination experiment under five irrigation levels with two dryland winter annuals (Biscutella didyma, Bromus fasciculatus) from four sites along the gradient. Species differed in means and evolvability of dormancy. Biscutella had high dormancy, which significantly increased with aridity but decreased with higher irrigation. In Bromus, dormancy was low, similar among populations, and only marginally affected by irrigation. Evolvability in Biscutella was high and varied among populations, without a clinal trend along the gradient. Conversely, in Bromus, trait evolvability was low and declined with increasing aridity. We argue that changes in evolvability along climatic gradients depend on the relative intensity of stabilizing selection. This may be high in Bromus and not only depends on environmental stress, but also on variability. Our findings point to the importance of measuring evolvability of climate‐related traits across different natural and artificial environments and for many coexisting species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 924–934.     

TEMPORAL VARIATION FAVORS THE EVOLUTION OF GENERALISTS IN EXPERIMENTAL POPULATIONS OF DROSOPHILA MELANOGASTER

In variable environments, selection should favor generalists that maintain fitness across a range of conditions. However, costs of adaptation may generate fitness trade‐offs and lead to some compromise between specialization and generalization that maximizes fitness. Here, we evaluate the evolution of specialization and generalization in 20 populations of Drosophila melanogaster experimentally evolved in constant and variable thermal environments for 3 years. We developed genotypes from each population at two temperatures after which we measured fecundity across eight temperatures. We predicted that constant environments would select for thermal specialists and that variable environments would select for thermal generalists. Contrary to our predictions, specialists and generalists did not evolve in constant and spatially variable environments, respectively. However, temporal variation produced a type of generalist that has rarely been considered by theoretical models of developmental plasticity. Specifically, genotypes from the temporally variable selective environment were more fecund across all temperatures than were genotypes from other environments. These patterns suggest certain allelic effects and should inspire new directions for modeling adaptation to fluctuating environments.     

Parallel trait adaptation across opposing thermal environments in experimental Drosophila melanogaster populations

Thermal stress is a pervasive selective agent in natural populations that impacts organismal growth, survival, and reproduction. Drosophila melanogaster exhibits a variety of putatively adaptive phenotypic responses to thermal stress in natural and experimental settings; however, accompanying assessments of fitness are typically lacking. Here, we quantify changes in fitness and known thermal tolerance traits in replicated experimental D. melanogaster populations following more than 40 generations of evolution to either cyclic cold or hot temperatures. By evaluating fitness for both evolved populations alongside a reconstituted starting population, we show that the evolved populations were the best adapted within their respective thermal environments. More strikingly, the evolved populations exhibited increased fitness in both environments and improved resistance to both acute heat and cold stress. This unexpected parallel response appeared to be an adaptation to the rapid temperature changes that drove the cycling thermal regimes, as parallel fitness changes were not observed when tested in a constant thermal environment. Our results add to a small, but growing group of studies that demonstrate the importance of fluctuating temperature changes for thermal adaptation and highlight the need for additional work in this area.     

Escherichia coli populations adapt to complex,unpredictable fluctuations by minimizing trade‐offs across environments

In nature, organisms are simultaneously exposed to multiple stresses (i.e. complex environments) that often fluctuate unpredictably. Although both these factors have been studied in isolation, the interaction of the two remains poorly explored. To address this issue, we selected laboratory populations of Escherichia coli under complex (i.e. stressful combinations of pH, H₂O₂ and NaCl) unpredictably fluctuating environments for ~900 generations. We compared the growth rates and the corresponding trade‐off patterns of these populations to those that were selected under constant values of the component stresses (i.e. pH, H₂O₂ and NaCl) for the same duration. The fluctuation‐selected populations had greater mean growth rate and lower variation for growth rate over all the selection environments experienced. However, whereas the populations selected under constant stresses experienced trade‐offs in the environments other than those in which they were selected, the fluctuation‐selected populations could bypass the across‐environment trade‐offs almost entirely. Interestingly, trade‐offs were found between growth rates and carrying capacities. The results suggest that complexity and fluctuations can strongly affect the underlying trade‐off structure in evolving populations.     

Genotype‐environment interactions rule the response of a widespread butterfly to temperature variation

Understanding how organisms adapt to complex environments is a central goal of evolutionary biology and ecology. This issue is of special interest in the current era of rapidly changing climatic conditions. Here, we investigate clinal variation and plastic responses in life history, morphology and physiology in the butterfly Pieris napi along a pan‐European gradient by exposing butterflies raised in captivity to different temperatures. We found clinal variation in body size, growth rates and concomitant development time, wing aspect ratio, wing melanization and heat tolerance. Individuals from warmer environments were more heat‐tolerant and had less melanised wings and a shorter development, but still they were larger than individuals from cooler environments. These findings suggest selection for rapid growth in the warmth and for wing melanization in the cold, and thus fine‐tuned genetic adaptation to local climates. Irrespective of the origin of butterflies, the effects of higher developmental temperature were largely as expected, speeding up development; reducing body size, potential metabolic activity and wing melanization; while increasing heat tolerance. At least in part, these patterns likely reflect adaptive phenotypic plasticity. In summary, our study revealed pronounced plastic and genetic responses, which may indicate high adaptive capacities in our study organism. Whether this may help such species, though, to deal with current climate change needs further investigation, as clinal patterns have typically evolved over long periods.