Comparative floral and vegetative differentiation between two European Aquilegia taxa along a narrow contact zone

As a first step in determining the identity and relative importance of the evolutionary forces promoting the speciation process in two closely related European taxa of Aquilegia, we investigated the levels of morphological variation in floral and vegetative characters over the narrow region where their ranges enter into contact, and evaluate the relative importance of both types of traits in their differentiation. A total of 12 floral and ten vegetative characters were measured on 375 plants belonging to seven A. vulgaris populations and six A. pyrenaica subsp. cazorlensis populations located in southeastern Spain. Floral and vegetative morphological differentiation occur between taxa and among populations within taxa, but only vegetative characters (particularly plant height and leaf petiolule length) contribute significantly to the discrimination between taxa. Differentiation among populations within taxa is mostly explained by variation in floral traits. Consequently, morphological divergence between the two taxa cannot be interpreted as an extension of among-population differences occurring within taxa. Multivariate vegetative, but not floral, similarity between populations could be predicted from geographical distance. Moreover, the key role of certain vegetative traits in the differentiation of A. vulgaris and A. p. cazorlensis could possibly be attributable to the contrasting habitat requirements and stress tolerance strategies of the two taxa. These preliminary findings seem to disagree with the currently established view of the radiation process in the genus Aquilegia in North America, where the differentiation of floral traits seems to have played a more important role.     

TYPE I ERROR RATES FOR TESTING GENETIC DRIFT WITH PHENOTYPIC COVARIANCE MATRICES: A SIMULATION STUDY

Studies of evolutionary divergence using quantitative genetic methods are centered on the additive genetic variance–covariance matrix ( G ) of correlated traits. However, estimating G properly requires large samples and complicated experimental designs. Multivariate tests for neutral evolution commonly replace average G by the pooled phenotypic within‐group variance–covariance matrix ( W ) for evolutionary inferences, but this approach has been criticized due to the lack of exact proportionality between genetic and phenotypic matrices. In this study, we examined the consequence, in terms of type I error rates, of replacing average G by W in a test of neutral evolution that measures the regression slope between among‐population variances and within‐population eigenvalues (the Ackermann and Cheverud [AC] test) using a simulation approach to generate random observations under genetic drift. Our results indicate that the type I error rates for the genetic drift test are acceptable when using W instead of average G when the matrix correlation between the ancestral G and P is higher than 0.6, the average character heritability is above 0.7, and the matrices share principal components. For less‐similar G and P matrices, the type I error rates would still be acceptable if the ratio between the number of generations since divergence and the effective population size (t/N_e) is smaller than 0.01 (large populations that diverged recently). When G is not known in real data, a simulation approach to estimate expected slopes for the AC test under genetic drift is discussed.     

Experimental studies of adaptation in Clarkia xantiana. I. Sources of trait variation across a subspecies border

Abstract Both genetic differentiation and phenotypic plasticity might be expected to affect the location of geographic range limits. Co‐gradient variation (CoGV), plasticity that is congruent with genetic differentiation, may enhance performance at range margins, whereas its opposite, counter‐gradient variation (CnGV) may hinder performance. Here we report findings of reciprocal transplant experiments intended to tease apart the roles of differentiation and plasticity in producing phenotypic variation across a geographic border between two plant subspecies. Clarkia xantiana ssp. xantiana and C. xantiana ssp. parviflora are California‐endemic annuals that replace each other along a west‐east gradient of declining precipitation. We analyzed variation in floral traits, phenological traits, and vegetative morphological and developmental traits by sowing seeds of 18 populations (six of ssp. xantiana and 12 of ssp. parviflora) at three sites (one in each subspecies' exclusive range and one in the subspecies' contact zone), in two growing seasons (an exceptionally wet El Niño winter and a much drier La Niña winter). Significant genetic differences between subspecies appeared in 11 of 12 traits, and differences were of the same sign as in nature. These findings are consistent with the hypothesis that selection is responsible for subspecies differences. Geographic variation within subspecies over part of the spatial gradient mirrored between‐subspecies differences present at a larger scale. All traits showed significant plasticity in response to spatial and temporal environmental variation. Plasticity patterns ranged from spatial and temporal CoGV (e.g., in node of first flower), to spatial CnGV (e.g., in flowering time), to patterns that were neither CoGV nor CnGV (the majority of traits). Instances of CoGV may reflect adaptive plasticity and may serve to increase performance under year‐to‐year environmental variation and at sites near the subspecies border. However, the presence of spatial CnGV in some critical traits suggests that subspecies ranges may also be constrained by patterns of plasticity.     

Plant performance and morpho-functional differentiation in response to edaphic variation in Iberian columbines: cues for range distribution?

Aims Experimental studies of the response to environmental variation of closely related taxa are needed to understand the mechanisms underlying phenotypic divergence, habitat segregation and range span within a radiating genus. We explored the magnitude of phenotypic differentiation and adaptive plasticity in relation to edaphic variation and its significance for habitat segregation and range span in Iberian columbines.Methods We performed a common garden experiment varying soil type (calcareous vs. siliceous) and depth (rocky-shallow vs. deep) with two pairs of widespread and narrowly distributed subspecies of Iberian columbines: Aquilegia vulgaris (subspp. vulgaris and nevadensis) and Aquilegia pyrenaica (subspp. pyrenaica and cazorlensis). We compared tolerance to edaphic variation, trait differentiation and adaptive plasticity of 10 morpho-functional traits between species and distribution ranges. Additionally, we obtained estimates of the competitive environment faced by each taxon in two to four populations per taxa.Important findings Results partially support hypotheses of higher competitive ability and tolerance to edaphic variation in widespread than in narrow endemic taxa. At the species level, the widely distributed taxon was the most tolerant to edaphic variation. Within species, no consistent pattern emerged since the population from the most widespread subspecies was the most tolerant in A. vulgaris but not in A. pyrenaica. Columbines were differentiated in many traits at species and range level. However, the pattern of differentiation does not fully support the hypothesis of higher specialization and stress tolerance in narrow endemics. Although plasticity was generally low, the results support the hypothesis of adaptive plasticity in widespread but not in restricted taxa at least at species level. Ecological differences (adaptive plasticity and competitive ability among others) may have contributed to phenotypic divergence and edaphic niche segregation, as well as to differences in range span among columbines.     

Pleiotropic quantitative trait loci contribute to population divergence in traits associated with life-history variation in Mimulus guttatus

Evolutionary biologists seek to understand the genetic basis for multivariate phenotypic divergence. We constructed an F2 mapping population (N = 539) between two distinct populations of Mimulus guttatus. We measured 20 floral, vegetative, and life-history characters on parents and F1 and F2 hybrids in a common garden experiment. We employed multitrait composite interval mapping to determine the number, effect, and degree of pleiotropy in quantitative trait loci (QTL) affecting divergence in floral, vegetative, and life-history characters. We detected 16 QTL affecting floral traits; 7 affecting vegetative traits; and 5 affecting selected floral, vegetative, and life-history traits. Floral and vegetative traits are clearly polygenic. We detected a few major QTL, with all remaining QTL of small effect. Most detected QTL are pleiotropic, implying that the evolutionary shift between these annual and perennial populations is constrained. We also compared the genetic architecture controlling floral trait divergence both within (our intraspecific study) and between species, on the basis of a previously published analysis of M. guttatus and M. nasutus. Eleven of our 16 floral QTL map to approximately the same location in the interspecific map based on shared, collinear markers, implying that there may be a shared genetic basis for floral divergence within and among species of Mimulus.     

QUANTITATIVE GENETICS OF MORPHOLOGICAL DIFFERENTIATION IN PEROMYSCUS. I. TESTS OF THE HOMOGENEITY OF GENETIC COVARIANCE STRUCTURE AMONG SPECIES AND SUBSPECIES

Phenotypic and additive genetic covariance matrices were estimated for 15 morphometric characters in three species and subspecies of Peromyscus. Univariate and multivariate ANOVAs indicate these groups are highly diverged in all characters, P. leucopus having the largest body size, P. maniculatus bairdii the smallest, and P. maniculatus nebrascensis being intermediate. Comparing the structure of P and G within each taxon revealed significant similarities in all three cases. This proportionality was strong enough to justify using P in the place of G to analyze evolutionary processes using quantitative genetic models when G can not be estimated, as in fossil material. However, the similarity between genetic and phenotypic covariance structures is sufficiently low that estimates of the genetic parameters should be used when possible. The additive genetic covariance matrices were compared to examine the assumption that they remain constant during evolution, an assumption which underlies many applications of quantitative-genetic models. While matrix permutation tests indicated statistically significant proportionality between the genetic covariance structures of the two P. maniculatus subspecies, there is no evidence of significant genetic structural similarity between species. This result suggests that the assumption of constant genetic covariance structure may be valid only within species. (It does not, however, necessarily imply a causal relationship between speciation and heterogeneity of genetic covariance structures.) The low matrix correlation for the two P. maniculatus subspecies' genetic covariance matrices indicates G may not be functionally constant, even within species. The lack of similarity observed here may be due partly to sampling variation.     

Phenotypic evolution of an Atlantic Forest passerine (Xiphorhynchus fuscus): biogeographic and systematic implications

We studied the phenotypic variation of the Atlantic Forest passerine Xiphorhynchus fuscus (Aves: Dendrocolaptidae) with the broad aim of addressing whether the history and type of forest affected the evolution of endemic taxa. We also tested whether the different subspecies and genetic lineages of X. fuscus could be considered full species. We collected plumage and body size measurements and, in combination with genetic data, used multivariate tests to evaluate the working hypotheses. Our results, combined with previous biogeographic analyses, indicate that vicariant events have been important determinants in the evolution of phenotypic characters of X. fuscus, once genetic isolation was complete. Our analysis also suggests that forest heterogeneity and ecotones are important factors in the early evolution of Atlantic Forest taxa, perhaps via divergent selection. Forest instability during the Pleistocene was critical in the evolution of phenotypic traits. We confirm that the subspecies atlanticus should be considered a full species. Other lineages or populations are also phenotypically differentiated but we do not suggest considering them as full species. They share high levels of gene flow and are part of a continuous latitudinal cline of phenotypic variation. Our study suggests that not all the historic events in the Atlantic Forest that affected the evolution of genetic lineages also influenced the evolution of phenotypic characters in the same direction and intensity. Undoubtedly, natural selection played a major role in the evolution of Atlantic Forest organisms. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 1047–1066.     

Quantitative genetic parameters for wild stream‐living brown trout: heritability and parental effects

Adaptability depends on the presence of additive genetic variance for important traits. Yet few estimates of additive genetic variance and heritability are available for wild populations, particularly so for fishes. Here, we estimate heritability of length‐at‐age for wild‐living brown trout (Salmo trutta), based on long‐term mark‐recapture data and pedigree reconstruction based on large‐scale genotyping at 15 microsatellite loci. We also tested for the presence of maternal and paternal effects using a Bayesian version of the Animal model. Heritability varied between 0.16 and 0.31, with reasonable narrow confidence bands, and the total phenotypic variance increased with age. When introducing dam as an additional random effect (accounting for c. 7% of total phenotypic variance), the level of additive genetic variance and heritability decreased (0.12–0.21). Parental size (both for sires and for dams) positively influenced length‐at‐age for juvenile trout – either through direct parental effects or through genotype‐environment correlations. Length‐at‐age is a complex trait reflecting the effects of a number of physiological, behavioural and ecological processes. Our data show that fitness‐related traits such as length‐at‐age can retain high levels of additive genetic variance even when total phenotypic variance is high.     

Intra-population comparison of vegetative and floral trait heritabilities estimated from molecular markers in wild Aquilegia populations

Measuring heritable genetic variation is important for understanding patterns of trait evolution in wild populations, and yet studies of quantitative genetic parameters estimated directly in the field are limited by logistic constraints, such as the difficulties of inferring relatedness among individuals in the wild. Marker-based approaches have received attention because they can potentially be applied directly to wild populations. For long-lived, self-compatible plant species where pedigrees are inadequate, the regression-based method proposed by Ritland has the appeal of estimating heritabilities from marker-based estimates of relatedness. The method has been difficult to implement in some plant populations, however, because it requires significant variance in relatedness across the population. Here, we show that the method can be readily applied to compare the ability of different traits to respond to selection, within populations. For several taxa of the perennial herb genus Aquilegia, we estimated heritabilities of floral and vegetative traits and, combined with estimates of natural selection, compared the ability to respond to selection of both types of traits under current conditions. The intra-population comparisons showed that vegetative traits have a higher potential for evolution, because although they are as heritable as floral traits, selection on them is stronger. These patterns of potential evolution are consistent with macroevolutionary trends in the European lineage of the genus.     

Population mixing and the adaptive divergence of quantitative traits in discrete populations: a theoretical framework for empirical tests

Empirical tests for the importance of population mixing in constraining adaptive divergence have not been well grounded in theory for quantitative traits in spatially discrete populations. We develop quantitative-genetic models to examine the equilibrium difference between two populations that are experiencing different selective regimes and exchanging individuals. These models demonstrate that adaptive divergence is negatively correlated with the rate of population mixing (m, most strongly so when m is low), positively correlated with the difference in phenotypic optima between populations, and positively correlated with the amount of additive genetic variance (G, most strongly so when G is low). The approach to equilibrium is quite rapid (fewer than 50 generations for two populations to evolve 90% of the distance to equilibrium) when either heritability or mixing are not too low (h2 > 0.2 or m > 0.05). The theory can be used to aid empirical tests that: (1) compare observed divergence to that predicted using estimates of population mixing, additive genetic variance/covariance, and selection; (2) test for a negative correlation between population mixing and adaptive divergence across multiple independent population pairs; and (3) experimentally manipulate the rate of mixing. Application of the first two of these approaches to data from two well-studied natural systems suggests that population mixing has constrained adaptive divergence for color patterns in Lake Erie water snakes (Nerodia sipedon), but not for trophic traits in sympatric pairs of benthic and limnetic stickleback (Gasterosteus aculeatus). The theoretical framework we outline should provide an improved basis for future empirical tests of the role of population mixing in adaptive divergence.     

Heritability and genetic correlations of personality traits in a wild population of yellow‐bellied marmots (Marmota flaviventris)

Describing and quantifying animal personality is now an integral part of behavioural studies because individually distinctive behaviours have ecological and evolutionary consequences. Yet, to fully understand how personality traits may respond to selection, one must understand the underlying heritability and genetic correlations between traits. Previous studies have reported a moderate degree of heritability of personality traits, but few of these studies have either been conducted in the wild or estimated the genetic correlations between personality traits. Estimating the additive genetic variance and covariance in the wild is crucial to understand the evolutionary potential of behavioural traits. Enhanced environmental variation could reduce heritability and genetic correlations, thus leading to different evolutionary predictions. We estimated the additive genetic variance and covariance of docility in the trap, sociability (mirror image stimulation), and exploration and activity in two different contexts (open‐field and mirror image simulation experiments) in a wild population of yellow‐bellied marmots (Marmota flaviventris). We estimated both heritability of behaviours and of personality traits and found nonzero additive genetic variance in these traits. We also found nonzero maternal, permanent environment and year effects. Finally, we found four phenotypic correlations between traits, and one positive genetic correlation between activity in the open‐field test and sociability. We also found permanent environment correlations between activity in both tests and docility and exploration in the MIS test. This is one of a handful of studies to adopt a quantitative genetic approach to explain variation in personality traits in the wild and, thus, provides important insights into the potential variance available for selection.     

Floral integration,phenotypic covariance structure and pollinator variation in bumblebee‐pollinated Helleborus foetidus

By analysing patterns of phenotypic integration and multivariate covariance structure of five metric floral traits in nine Iberian populations of bumblebee‐pollinated Helleborus foetidus (Ranunculaceae), this paper attempts to test the general hypothesis that pollinators enhance floral integration and selectively modify phenotypic correlations between functionally linked floral traits. The five floral traits examined exhibited significant phenotypic integration at all populations, and both the magnitude and the pattern of integration differed widely among populations. Variation in extent and pattern of integration was neither distance‐dependent nor significantly related to between‐population variation in taxonomical composition and morphological diversity of the pollinator assemblage. Patterns of floral integration were closer to expectations derived from consideration of developmental affinities between floral whorls than to expectations based on a pollinator‐mediated adaptive hypothesis. Taken together, results of this study suggest that between‐population differences in magnitude and pattern of floral integration in H. foetidus are probably best explained as a consequence of random genetic sampling in the characteristically small and ephemeral populations of this species, rather than reflecting the selective action of current pollinators.     

Evolutionary potential in the wild: more than meets the eye

The genus Aquilegia consists of 60–70 perennial plant species widely distributed throughout the northern hemisphere. Its flowers have a delicate and ornamental appearance that makes them a favourite of gardeners. In this genus, adaptive radiations for both floral and vegetative traits have occurred. These adaptive radiations, and the key phylogenetic placement of Aquilegia between Arabidopsis and rice, make this genus a ‘model system’ for plant evolution ( Kramer 2009 ). In this issue, Castellanos et al. (2011) use a marker‐based method to infer heritability for floral and vegetative traits in two Aquilegia species. Layered on top of this are estimates of the strength of natural selection. This novel joint estimation of heritability and selection in the wild showed that vegetative traits, compared to floral traits, have the highest evolutionarily potential. Evolutionary potential is the most important quantity to measure in wild populations. It combines inheritance and strength of selection and predicts the potential for populations to adapt to changing environments. The combination of molecular techniques with species in natural environments makes this work a model for molecular ecological investigations.     

QUANTITATIVE GENETICS OF MORPHOLOGICAL DIFFERENTIATION IN PEROMYSCUS. II. ANALYSIS OF SELECTION AND DRIFT

The hypothesis that the morphological divergence of local populations of Peromyscus is due to random genetic drift was evaluated by testing the proportionality of the among-locality covariance matrix, L, and the additive genetic covariance matrix, G. Overall, significant proportionality of L? and ? was not observed, indicating the evolutionary divergence of local populations does not result from random genetic drift. The forces of selection needed to differentiate three taxa of Peromyscus were reconstructed to examine the divergence of species and subspecies. The selection gradients obtained illustrate the inadequacy of univariate analyses of selection by finding that some characters evolve in the direction opposite to the force of selection acting directly on them. A retrospective selection index was constructed using the estimated selection gradients, and truncation selection on this index was used to estimate the minimum selective mortality per generation required to produce the observed change. On any of the time scales used, the proportion of the population that would need to be culled was quite low, the greatest being of the same order of magnitude as the selective intensities observed in extant natural populations. Thus, entirely plausible intensities of directional natural selection can produce species-level differences in a period of time too short to be resolved in the fossil record.     

Expression of additive genetic variances and covariances for wild radish floral traits: comparison between field and greenhouse environments

Measurements of the genetic variation and covariation underlying quantitative traits are crucial to our understanding of current evolutionary change and the mechanisms causing this evolution. This fact has spurred a large number of studies estimating heritabilities and genetic correlations in a variety of organisms. Most of these studies have been done in laboratory or greenhouse settings, but it is not well known how accurately these measurements estimate genetic variance and covariance expressed in the field. We conducted a quantitative genetic half-sibling analysis on six floral traits in wild radish. Plants were grown from seed in the field and were exposed to natural environmental variation throughout their lives, including herbivory and intra- and interspecific competition. The estimates of heritabilities and the additive genetic variance-covariance matrix (G) obtained from this analysis were then compared to previous greenhouse estimates of the same floral traits from the same natural population. Heritabilities were much lower in the field for all traits, and this was due to both large increases in environmental variance and decreases in additive genetic variance. Additive genetic covariance expressed was also much lower in the field. These differences resulted in highly significant differences in the G matrix between the greenhouse and field environments using two complementary testing methods. Although the G matrices shared some principal components in common, they were not simply proportional to each other. Therefore, the greenhouse results did not accurately depict how the floral traits would respond to natural selection in the field.     

Small‐scale spatial variation in evolvability for life‐history traits in the storm petrel

The evolutionary potential in the timing of recruitment and reproduction may be crucial for the ability of populations to buffer against environmental changes, allowing them to avoid unfavourable breeding conditions. The evolution of a trait in a local population is determined by its heritability and selection. In the present study, we performed pedigree‐based quantitative genetic analyses for two life‐history traits (recruiting age and laying date) using population data of the storm petrel over an 18‐year period in two adjacent breeding colonies (only 150 m apart) that share the same environmental conditions. In both traits, natal colony effect was the main source of the phenotypic variation among individuals, and cohort variance for recruitment age and additive genetic variance for laying date were natal colony‐specific. We found significant heritability only in laying date and, more specifically, only in birds born in one of the colonies. The difference in genetic variance between the colonies was statistically significant. Interestingly, selection on earlier breeding birds was detected only in the colony in which heritable variation in laying date was found. Therefore, local evolvability for a life‐history trait may vary within a unexpectedly small spatial scale, through the diversifying natural selection and insulating gene flow. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 439–446.     

Genetic and environmental variations in quantitative characters in fishes: a comparative analysis of monoclonal triploid and bisexual tetraploid spined loaches (<Emphasis Type="Italic">Cobitis</Emphasis>, Cobitidae)

The heritability estimates of 25 external morphometric characters and 23 craniometric indices are obtained by use of variances in monoclonal all-female triploids and bisexual tetraploids of spined loaches (genus Cobitis, Cobitidae) collected from the same breeding biotope. Most of studied traits demonstrate low heritability confirming previous conclusion on the similarity between external morphometric characters and craniological indices in relative effects of genetic and environmental components in their total phenotypic variation. Low heritability estimates in most of external morphological traits correspond to their low diagnostic value in Cobitis species. As a whole, in spite of certain deviations, studies on clonal forms do not refute the concept on higher heritability estimates in diagnostically significant traits in comparison with traits without diagnostic values in the same taxonomic group. Low heritability in most morphometric traits more probably is resulted from their low additive genetic variation caused by strong selection of evolutionary developed specific body shape in spined loaches, because strong selection should reduce the genetic variance in body proportions to minimal size. Sex differences observed in heritability estimates should be interpreted as a result of linkage of several additive genes controlling these traits to sex chromosomes. A few characters demonstrating high heritability estimates up to 0.492–0.580 are of great interest for taxonomic and phylogenetic studies in genus Cobitis and related taxa.     

Floral trait differentiation in Anacamptis coriophora: Phenotypic selection on scents,but not on colour

Current divergent selection may promote floral trait differentiation among conspecific populations in flowering plants. However, whether this applies to complex traits such as colour or scents has been little studied, even though these traits often vary within species. In this study, we compared floral colour and odour as well as selective pressures imposed upon these traits among seven populations belonging to three subspecies of the widespread, generalist orchid Anacamptis coriophora. Colour was characterized using calibrated photographs, and scents were sampled using dynamic headspace extraction and analysed using gas chromatography–mass spectrometry. We then quantified phenotypic selection exerted on these traits by regressing fruit set values on floral trait values. We showed that the three studied subspecies were characterized by different floral colour and odour, with one of the two predominant floral volatiles emitted by each subspecies being taxon‐specific. Plant size was positively correlated with fruit set in most populations, whereas we found no apparent link between floral colour and female reproductive success. We detected positive selection on several taxon‐specific compounds in A. coriophora subsp. fragrans, whereas no selection was found on floral volatiles of A. coriophora subsp. coriophora and A. coriophora subsp. martrinii. This study is one of the first to document variation in phenotypic selection exerted on floral scents among conspecific populations. Our results suggest that selection could contribute to ongoing chemical divergence among A. coriophora subspecies.     

Morphometric analysis and taxonomic revision of the Vriesea paraibica complex (Bromeliaceae)

The species related to Vriesea paraibica (Bromeliaceae, Tillandsioideae) have controversial taxonomic limits. For several decades, this group has been identified in herbarium collections as V. × morreniana, an artificial hybrid that does not grow in natural habitats. The aim of this study was to assess the morphological variation in the V. paraibica complex through morphometric analyses of natural populations. Two sets of analyses were performed: the first involved six natural populations (G1) and the second was carried out on taxa that emerged from the first analysis, but using material from herbarium collections (G2). Univariate ANOVA was used, as well as discriminant analysis of 16 morphometric variables in G1 and 18 in G2. The results of the analyses of the two groups were similar and led to the selection of diagnostic traits of four species. Lengths of the lower and median floral bracts were significant for the separation of red and yellow floral bracts. Vriesea paraibica and V. interrogatoria have red bracts; these two species are differentiated by the widths of the lower and median portions of the inflorescence and by scape length. These structures are larger in the former and smaller in the latter. Of the species with yellow floral bracts, V. eltoniana is distinguished by longer leaf blades and scapes and V. flava is characterized by its shorter sepal lengths. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 163–181.     

The genetic variance but not the genetic covariance of life‐history traits changes towards the north in a time‐constrained insect

Seasonal time constraints are usually stronger at higher than lower latitudes and can exert strong selection on life‐history traits and the correlations among these traits. To predict the response of life‐history traits to environmental change along a latitudinal gradient, information must be obtained about genetic variance in traits and also genetic correlation between traits, that is the genetic variance‐covariance matrix, G . Here, we estimated G for key life‐history traits in an obligate univoltine damselfly that faces seasonal time constraints. We exposed populations to simulated native temperatures and photoperiods and common garden environmental conditions in a laboratory set‐up. Despite differences in genetic variance in these traits between populations (lower variance at northern latitudes), there was no evidence for latitude‐specific covariance of the life‐history traits. At simulated native conditions, all populations showed strong genetic and phenotypic correlations between traits that shaped growth and development. The variance–covariance matrix changed considerably when populations were exposed to common garden conditions compared with the simulated natural conditions, showing the importance of environmentally induced changes in multivariate genetic structure. Our results highlight the importance of estimating variance–covariance matrixes in environments that mimic selection pressures and not only trait variances or mean trait values in common garden conditions for understanding the trait evolution across populations and environments.