Elevational gradients in constitutive and induced oak defences based on individual traits and their correlated expression patterns

Elevational gradients are useful ecological settings for revealing the biotic and abiotic drivers of plant trait variation and plant–insect interactions. However, most work focusing on plant defences has looked at individual traits and few studies have assessed multiple traits simultaneously, their correlated expression patterns, and abiotic factors associated with such patterns across elevations. To address this knowledge gap, we studied elevational variation in direct (phenolic compounds) and indirect (volatile organic compounds) constitutive defences and their inducibility after feeding by a specialist beetle Altica quercetorum in saplings of 18 wild populations of Quercus pyrenaica. We tested for: 1) clines in each defensive trait individually, 2) their patterns of correlated expression and 3) associations between any such clines and climatic factors. We found that constitutive direct defences (lignins and hydrolysable tannins) decreased with increasing elevation. We observed no elevational gradient for constitutive indirect defences (volatile organic compounds) or the inducibility of direct or indirect defensive traits when looking at groups of compounds. However, at individual tree-level, increased induction of two monoterpenes (α-fenchene and camphene) at higher elevation was shown. Furthermore, we show a significant pattern of co-expression of constitutive and induced phenolics across populations, which weakened with increasing elevation. Finally, we found no evidence that climatic factors were associated with either individual or correlated trait expression patterns across elevations. Overall, these findings call for moving beyond elevational clines in individual plant defences, and argue that assessing elevational shifts in trait correlated expression patterns and their underlying mechanisms can increase our understanding of plant defence evolution and plant–herbivore interactions along environmental gradients.     

Plasticity in functional traits in the context of climate change: a case study of the subalpine forb Boechera stricta (Brassicaceae)

Environmental variation often induces shifts in functional traits, yet we know little about whether plasticity will reduce extinction risks under climate change. As climate change proceeds, phenotypic plasticity could enable species with limited dispersal capacity to persist in situ, and migrating populations of other species to establish in new sites at higher elevations or latitudes. Alternatively, climate change could induce maladaptive plasticity, reducing fitness, and potentially stalling adaptation and migration. Here, we quantified plasticity in life history, foliar morphology, and ecophysiology in Boechera stricta (Brassicaceae), a perennial forb native to the Rocky Mountains. In this region, warming winters are reducing snowpack and warming springs are advancing the timing of snow melt. We hypothesized that traits that were historically advantageous in hot and dry, low‐elevation locations will be favored at higher elevation sites due to climate change. To test this hypothesis, we quantified trait variation in natural populations across an elevational gradient. We then estimated plasticity and genetic variation in common gardens at two elevations. Finally, we tested whether climatic manipulations induce plasticity, with the prediction that plants exposed to early snow removal would resemble individuals from lower elevation populations. In natural populations, foliar morphology and ecophysiology varied with elevation in the predicted directions. In the common gardens, trait plasticity was generally concordant with phenotypic clines from the natural populations. Experimental snow removal advanced flowering phenology by 7 days, which is similar in magnitude to flowering time shifts over 2–3 decades of climate change. Therefore, snow manipulations in this system can be used to predict eco‐evolutionary responses to global change. Snow removal also altered foliar morphology, but in unexpected ways. Extensive plasticity could buffer against immediate fitness declines due to changing climates.     

Plant population differentiation and climate change: responses of grassland species along an elevational gradient

Mountain ecosystems are particularly susceptible to climate change. Characterizing intraspecific variation of alpine plants along elevational gradients is crucial for estimating their vulnerability to predicted changes. Environmental conditions vary with elevation, which might influence plastic responses and affect selection pressures that lead to local adaptation. Thus, local adaptation and phenotypic plasticity among low and high elevation plant populations in response to climate, soil and other factors associated with elevational gradients might underlie different responses of these populations to climate warming. Using a transplant experiment along an elevational gradient, we investigated reproductive phenology, growth and reproduction of the nutrient‐poor grassland species Ranunculus bulbosus, Trifolium montanum and Briza media. Seeds were collected from low and high elevation source populations across the Swiss Alps and grown in nine common gardens at three different elevations with two different soil depths. Despite genetic differentiation in some traits, the results revealed no indication of local adaptation to the elevation of population origin. Reproductive phenology was advanced at lower elevation in low and high elevation populations of all three species. Growth and reproduction of T. montanum and B. media were hardly affected by garden elevation and soil depth. In R. bulbosus, however, growth decreased and reproductive investment increased at higher elevation. Furthermore, soil depth influenced growth and reproduction of low elevation R. bulbosus populations. We found no evidence for local adaptation to elevation of origin and hardly any differences in the responses of low and high elevation populations. However, the consistent advanced reproductive phenology observed in all three species shows that they have the potential to plastically respond to environmental variation. We conclude that populations might not be forced to migrate to higher elevations as a consequence of climate warming, as plasticity will buffer the detrimental effects of climate change in the three investigated nutrient‐poor grassland species.     

Elevational trends in life histories: revising the pace‐of‐life framework

Life‐history traits in birds, such as lifespan, age at maturity, and rate of reproduction, vary across environments and in combinations imposed by trade‐offs and limitations of physiological mechanisms. A plethora of studies have described the diversity of traits and hypothesized selection pressures shaping components of the survival–reproduction trade‐off. Life‐history variation appears to fall along a slow–fast continuum, with slow pace characterized by higher investment in survival over reproduction and fast pace characterized by higher investment in reproduction over survival. The Pace‐of‐Life Syndrome (POLS) is a framework to describe the slow–fast axis of variation in life‐history traits and physiological traits. The POLS corresponds to latitudinal gradients, with tropical birds exhibiting a slow pace of life. We examined four possible ways that the traits of high‐elevation birds might correspond to the POLS continuum: (i) rapid pace, (ii) tropical slow pace, (iii) novel elevational pace, or (iv) constrained pace. Recent studies reveal that birds breeding at high elevations in temperate zones exhibit a combination of traits creating a unique elevational pace of life with a central trade‐off similar to a slow pace but physiological trade‐offs more similar to a fast pace. A paucity of studies prevents consideration of the possibility of a constrained pace of life. We propose extending the POLS framework to include trait variation of elevational clines to help to investigate complexity in global geographic patterns.     

Avian life history variation along altitudinal gradients: an example with cardueline finches

Elevation has long been considered a major influence on the evolution of life-history traits. Most elevation-induced variation in life history traits has been attributed to changes in climate, duration of breeding season, predation, and food limitation. I use a phylogenetic approach to show that life histories are closely associated with breeding elevation in extant cardueline finches. Finches at high elevations had smaller clutches, fewer broods, and longer incubation periods. Neither food limitation nor nest predation appear to readily account for this strong elevational variation in cardueline life histories. However, juvenile survival may be greater at higher elevations as a result of prolonged parental care and shorter natal dispersal and can potentially compensate for reduced fecundity in high-elevation finches. Received: 28 September 1996 / Accepted: 24 March 1997     

The role of the tolerance–fecundity trade‐off in maintaining intraspecific seed trait variation in a widespread dimorphic herb

Coexistence of species with different seed sizes is a long‐standing issue in community ecology, and a trade‐off between fecundity and stress tolerance has been proposed to explain co‐occurrence in heterogeneous environments. Here we tested an intraspecific extension of this model: whether such trade‐off also explains seed trait variation among populations of widespread plants under stress gradients. We collected seeds from 14 populations of Plantago coronopus along the Atlantic coast in North Africa and Europe. This herb presents seed dimorphism, producing large basal seeds with a mucilaginous coat that facilitates water absorption (more stress tolerant), and small apical seeds without coats (less stress tolerant). We analysed variation among populations in number, size and mucilage production of basal and apical seeds, and searched for relationships between local environment and plant size. Populations under higher stress (higher temperature, lower precipitation, lower soil organic matter) had fewer seeds per fruit, higher predominance of basal relative to apical seeds, and larger basal seeds with thicker mucilaginous coats. These results strongly suggest a trade‐off between tolerance and fecundity at the fruit level underpins variation in seed traits among P. coronopus populations. However, seed production per plant showed the opposite pattern to seed production per fruit, and seemed related to plant size and other life‐cycle components, as an additional strategy to cope with environmental variation across the range. The tolerance–fecundity model may constitute, under stress gradients, a broader ecological framework to explain trait variation than the classical seed size–number compromise, although several fecundity levels and traits should be considered to understand the diverse strategies of widespread plants to maximise fitness in each set of local conditions.     

Contrasting patterns of intraspecific trait variability in native and non-native plant species along an elevational gradient on Tenerife,Canary Islands

Background and AimsNon-native plant species are not restricted to lowlands, but increasingly are invading high elevations. While for both native and non-native species we expected variability of plant functional traits due to the changing environmental conditions along elevational gradients, we additionally assumed that non-native species are characterized by a more acquisitive growth strategy, as traits reflecting such a strategy have been found to correlate with invasion success. Furthermore, the typical lowland introduction of non-native species coming from multiple origins should lead to higher trait variability within populations of non-native species specifically at low elevations, and they might therefore occupy a larger total trait space.MethodsAlong an elevational gradient ranging from 55 to 1925 m a.s.l. on Tenerife, we collected leaves from eight replicate individuals in eight evenly distributed populations of five native and six non-native forb species. In each population, we measured ten eco-morphological and leaf biochemical traits and calculated trait variability within each population and the total trait space occupied by native and non-native species.Key ResultsWe found both positive (e.g. leaf dry matter content) and negative (e.g. leaf N) correlations with elevation for native species, but only few responses for non-native species. For non-native species, within-population variability of leaf dry matter content and specific leaf area decreased with elevation, but increased for native species. The total trait space occupied by all non-native species was smaller than and a subset of that of native species.ConclusionsWe found little evidence that intraspecific trait variability is associated with the success of non-native species to spread towards higher elevations. Instead, for non-native species, our results indicate that intermediate trait values that meet the requirements of various conditions are favourable across the changing environmental conditions along elevational gradients. As a consequence, this might prevent non-native species from overcoming abruptly changing environmental conditions, such as when crossing the treeline.     

Proximate causes of altitudinal differences in body size in an agamid lizard

Body size is directly linked to key life history traits such as growth, fecundity, and survivorship. Identifying the causes of body size variation is a critical task in ecological and evolutionary research. Body size variation along altitudinal gradients has received considerable attention; however, the underlying mechanisms are poorly understood. Here, we compared the growth rate and age structure of toad‐headed lizards (Phrynocephalus vlangalii) from two populations found at different elevations in the Qinghai‐Tibetan Plateau. We used mark‐recapture and skeletochronological analysis to identify the potential proximate causes of altitudinal variation in body size. Lizards from the high‐elevation site had higher growth rates and attained slightly larger adult body sizes than lizards from the low‐elevation site. However, newborns produced by high‐elevation females were smaller than those by low‐elevation females. Von Bertalanffy growth estimates predicted high‐elevation individuals would reach sexual maturity at an earlier age and have a lower mean age than low‐elevation individuals. Relatively lower mean age for the high‐elevation population was confirmed using the skeletochronological analysis. These results support the prediction that a larger adult body size of high‐elevation P. vlangalii results from higher growth rates, associated with higher resource availability.     

Traits and climate are associated with first flowering day in herbaceous species along elevational gradients

Phenological responses to changing temperatures are known as “fingerprints of climate change,” yet these reactions are highly species specific. To assess whether different plant characteristics are related to these species‐specific responses in flowering phenology, we observed the first flowering day (FFD) of ten herbaceous species along two elevational gradients, representing temperature gradients. On the same populations, we measured traits being associated with (1) plant performance (specific leaf area), (2) leaf biochemistry (leaf C, N, P, K, and Mg content), and (3) water‐use efficiency (stomatal pore area index and stable carbon isotopes concentration). We found that as elevation increased, FFD was delayed for all species with a highly species‐specific rate. Populations at higher elevations needed less temperature accumulation to start flowering than populations of the same species at lower elevations. Surprisingly, traits explained a higher proportion of variance in the phenological data than elevation. Earlier flowering was associated with higher water‐use efficiency, higher leaf C, and lower leaf P content. In addition to that, the intensity of shifts in FFD was related to leaf N and K. These results propose that traits have a high potential in explaining phenological variations, which even surpassed the effect of temperature changes in our study. Therefore, they have a high potential to be included in future analyses studying the effects of climate change and will help to improve predictions of vegetation changes.     

Trait differentiation and adaptation of plants along elevation gradients

Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta‐analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genomewide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.     

Ecological gradient of sexual selection: elevation and song elaboration in finches

Ecological gradients in natural and sexual selection often result in evolutionary diversification of morphological, life history, and behavioral traits. In particular, elevational changes in habitat structure and climate not only covary with intensity of sexual selection in many taxa, but may also influence evolution of mating signals. Here we examined variation in courtship song in relation to elevation of breeding across cardueline finches-a subfamily of birds that occupies the widest elevational range of extant birds and shows extensive variation in life histories and sexual selection along this range. We predicted that decrease in sexual selection intensity with elevation of breeding documented in this clade would result in a corresponding evolutionary reduction in elaboration of courtship songs. We controlled for the effects of phylogeny, morphology, and habitat structure to uncover a predicted elevational decline in courtship song elaboration; species breeding at lower elevations sang more elaborated and louder songs compared to their sister species breeding at higher elevations. In addition, lower elevation species had longer songs with more notes, whereas frequency components of song did not vary with elevation. We suggest that changes in sexual selection account for the observed patterns of song variation and discuss how elevational gradient in sexual selection may facilitate divergence in mating signals potentially reinforcing or promoting speciation.     

Elevational speciation in action? Restricted gene flow associated with adaptive divergence across an altitudinal gradient

Evolutionary theory predicts that divergent selection pressures across elevational gradients could cause adaptive divergence and reproductive isolation in the process of ecological speciation. Although there is substantial evidence for adaptive divergence across elevation, there is less evidence that this restricts gene flow. Previous work in the boreal chorus frog (Pseudacris maculata) has demonstrated adaptive divergence in morphological, life history and physiological traits across an elevational gradient from approximately 1500–3000 m in the Colorado Front Range, USA. We tested whether this adaptive divergence is associated with restricted gene flow across elevation – as would be expected if incipient speciation were occurring – and, if so, whether behavioural isolation contributes to reproductive isolation. Our analysis of 12 microsatellite loci in 797 frogs from 53 populations revealed restricted gene flow across elevation, even after controlling for geographic distance and topography. Calls also varied significantly across elevation in dominant frequency, pulse number and pulse duration, which was partly, but not entirely, due to variation in body size and temperature across elevation. However, call variation did not result in strong behavioural isolation: in phonotaxis experiments, low‐elevation females tended to prefer an average low‐elevation call over a high‐elevation call, and vice versa for high‐elevation females, but this trend was not statistically significant. In summary, our results show that adaptive divergence across elevation restricts gene flow in P. maculata, but the mechanisms for this potential incipient speciation remain open.     

Phenotypic differentiation of the Solidago virgaurea complex along an elevational gradient: Insights from a common garden experiment and population genetics

Plant species distributed along wide elevational or latitudinal gradients show phenotypic variation due to their heterogeneous habitats. This study investigated whether phenotypic variation in populations of the Solidago virgaurea complex along an elevational gradient is caused by genetic differentiation. A common garden experiment was based on seeds collected from nine populations of the S. virgaurea complex growing at elevations from 1,597 m to 2,779 m a.s.l. on Mt. Norikura in central Japan. Population genetic analyses with microsatellite markers were used to infer the genetic structure and levels of gene flow between populations. Leaf mass per area was lower, while leaf nitrogen and chlorophyll concentrations were greater for higher elevations at which seeds were originally collected. For reproductive traits, plants derived from higher elevations had larger flower heads on shorter stems and flowering started earlier. These elevational changes in morphology were consistent with the clines in the field, indicating that phenotypic variation along the elevational gradient would have been caused by genetic differentiation. However, population genetic analysis using 16 microsatellite loci suggested an extremely low level of genetic differentiation of neutral genes among the nine populations. Analysis of molecular variance also indicated that most genetic variation was partitioned into individuals within a population, and the genetic differentiation among the populations was not significant. This study suggests that genome regions responsible for adaptive traits may differ among the populations despite the existence of gene flow and that phenotypic variation of the S. virgaurea complex along the elevational gradient is maintained by strong selection pressure.     

Ecological and historical determinants of population genetic structure and diversity in the Mediterranean shrub Rosmarinus officinalis (Lamiaceae)

Population genetic studies of widespread Mediterranean shrubs are scarce compared with those of trees and narrow endemics or studies from phylogeographical perspectives, despite the key role these species may play in Mediterranean ecosystems. Knowledge on the effect of ecological factors in shaping their genetic patterns is also limited. In this study we investigate genetic diversity and population structure across 18 populations of Rosmarinus officinalis, a Mediterranean shrubland plant. Populations were sampled along two elevational gradients, one each on calcareous and siliceous soils in a mountain system in the eastern Iberian Peninsula, to decipher the effect of ecological factors on the genetic diversity and structure based on 11 microsatellite loci. We found overall high levels of genetic diversity and weak population structure. Genetic diversity increased with elevation, whereas population differentiation was stronger among populations growing on siliceous soils. The nested analysis of elevational gradients within soil types revealed that these general patterns were mostly driven by siliceous populations, whereas calcareous populations were more homogeneous along elevational belts. Bayesian analysis of population structure revealed genetic membership of lowland and high‐elevation populations to different genetic clusters and a higher admixture of intermediate‐elevation populations to both clusters. High‐elevation populations were less differentiated from a hypothetical ancestral cluster, suggesting the persistence of their gene pool during the Pleistocene glaciations. In contrast, lowland populations resulted from more recent divergence. We propose that life‐history and reproductive traits mostly contribute to explain the high levels of genetic diversity and weak population structure, whereas ecological and historical factors mostly contribute to the stronger differentiation of siliceous populations and a rapid expansion of R. officinalis on calcareous soils possibly mediated by human landscape transformations, © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2016, 180 , 50–63.     

Rapid evolution of thermal plasticity in mountain lake Daphnia populations

Populations at risk of extinction due to climate change may be rescued by adaptive evolution or plasticity. Selective agents, such as introduced predators, may enhance or constrain plastic or adaptive responses to temperature. We tested responses of Daphnia to temperature by collecting populations from lakes across an elevational gradient in the presence and absence of fish predators (long‐term selection). We subsequently grew these populations at two elevations in field mesocosms over two years (short‐term selection), followed by a common‐garden experiment at two temperatures in the lab to measure life‐history traits. Both long‐term and short‐term selection affected traits, suggesting that genetic variation of plasticity within populations enabled individuals to rapidly evolve plasticity in response to high temperature. We found that short‐term selection by high temperature increased plasticity for growth rate in all populations. Fecundity was higher in populations from fishless lakes and body size showed greater plasticity in populations from warm lakes (long‐term selection). Neither body size nor fecundity were affected by short‐term thermal selection. These results demonstrate that plasticity is an important component of the life‐history response of Daphnia, and that genetic variation within populations enabled rapid evolution of plasticity in response to selection by temperature.     

Scale‐dependent thermal tolerance variation in Australian mountain grasshoppers

Physiological variation among and within species is thought to play a key role in determining distribution patterns across environmental gradients. We tested inter‐ and intraspecific variation in cold and heat tolerances for three grasshopper species (genus Kosciuscola) with overlapping elevation distributions, across their respective ranges in the Australian mountains. Of the three cold tolerance traits measured, the critical thermal minimum was the only trait to vary among species, with greater cold tolerance associated with a distribution extending to a higher elevation. Cold tolerance limits were regularly exceeded in exposed microhabitats, suggesting a role for cold adaptation in structuring species distribution patterns. In contrast to cold tolerance, heat tolerance variation was primarily partitioned within species. For two species, populations from treeless alpine habitat were more heat tolerant than their lower‐elevation counterparts, supporting recent models that suggest greater exposure to temperature extremes at higher elevations. These contrasting patterns of physiological variation among and within species emphasise the importance of considering variation within species when attempting to understand how species distributions are affected by thermal extremes.     

Characterizing the contribution of plasticity and genetic differentiation to community‐level trait responses to environmental change

The match between functional trait variation in communities and environmental gradients is maintained by three processes: phenotypic plasticity and genetic differentiation (intraspecific processes), and species turnover (interspecific). Recently, evidence has emerged suggesting that intraspecific variation might have a potentially large role in driving functional community composition and response to environmental change. However, empirical evidence quantifying the respective importance of phenotypic plasticity and genetic differentiation relative to species turnover is still lacking. We performed a reciprocal transplant experiment using a common herbaceous plant species (Oxalis montana) among low‐, mid‐, and high‐elevation sites to first quantify the contributions of plasticity and genetic differentiation in driving intraspecific variation in three traits: height, specific leaf area, and leaf area. We next compared the contributions of these intraspecific drivers of community trait–environment matching to that of species turnover, which had been previously assessed along the same elevational gradient. Plasticity was the dominant driver of intraspecific trait variation across elevation in all traits, with only a small contribution of genetic differentiation among populations. Local adaptation was not detected to a major extent along the gradient. Fitness components were greatest in O. montana plants with trait values closest to the local community‐weighted means, thus supporting the common assumption that community‐weighted mean trait values represent selective optima. Our results suggest that community‐level trait responses to ongoing climate change should be mostly mediated by species turnover, even at the small spatial scale of our study, with an especially small contribution of evolutionary adaptation within species.     

Global patterns of intraspecific leaf trait responses to elevation

Elevational gradients are often used to quantify how traits of plant species respond to abiotic and biotic environmental variations. Yet, such analyses are frequently restricted spatially and applied along single slopes or mountain ranges. Since we know little on the response of intraspecific leaf traits to elevation across the globe, we here perform a global meta‐analysis of leaf traits in 109 plant species located in 4 continents and reported in 71 studies published between 1983 and 2018. We quantified the intraspecific change in seven morpho‐ecophysiological leaf traits along global elevational gradients: specific leaf area (SLA), leaf mass per area (LMA), leaf area (LA), nitrogen concentration per unit of area (Narea), nitrogen concentration per unit mass (Nmass), phosphorous concentration per unit mass (Pmass) and carbon isotope composition (δ¹³C). We found LMA, Narea, Nmass and δ¹³C to significantly increase and SLA to decrease with increasing elevation. Conversely, LA and Pmass showed no significant pattern with elevation worldwide. We found significantly larger increase in Narea, Nmass, Pmass and δ¹³C with elevation in warmer regions. Larger responses to increasing elevation were apparent for SLA of herbaceous compared to woody species, but not for the other traits. Finally, we also detected evidences of covariation across morphological and physiological traits within the same elevational gradient. In sum, we demonstrate that there are common cross‐species patterns of intraspecific leaf trait variation across elevational gradients worldwide. Irrespective of whether such variation is genetically determined via local adaptation or attributed to phenotypic plasticity, the leaf trait patterns quantified here suggest that plant species are adapted to live on a range of temperature conditions. Since the distribution of mountain biota is predominantly shifting upslope in response to changes in environmental conditions, our results are important to further our understanding of how plants species of mountain ecosystems adapt to global environmental change.     

No effect of elevation and fragmentation on genetic diversity and structure in Polylepis australis trees from central Argentina

Phenological differences in flowering arising along elevational gradients may be caused by either local adaptation or phenotypic plasticity. Local adaptation can lead to reproductive isolation of populations at different elevational zones and thus produce elevational genetic structuring, while phenotypic plasticity does not produce elevational genetic structuring. In this study, we examined the effects of elevation and fragmentation on genetic diversity and structure of Polylepis australis populations, where individuals exhibit phenological differences in flowering along an elevational gradient. We assessed the polymorphism of amplified fragment length polymorphism markers in adults and saplings from one conserved and one fragmented forest covering elevations from 1600 to 2600 m asl. Over 98% of variation was found within populations, and we found very low and similar genetic differentiation along elevational gradients for adults and saplings in both continuous and fragmented forests. In addition, there was no significant relationship between genetic diversity and elevation. Results indicated that phenological differences along elevational gradients are more likely caused by phenotypic plasticity than local adaptation, and fragmentation does not appear to have affected genetic diversity and differentiation in the studied populations. Results therefore imply that if necessary, seeds for reforestation purposes may be collected from different elevations to the seeding or planting sites.     

Length of activity season drives geographic variation in body size of a widely distributed lizard

Understanding the factors that drive geographic variation in life history is an important challenge in evolutionary ecology. Here, we analyze what predicts geographic variation in life‐history traits of the common lizard, Zootoca vivipara, which has the globally largest distribution range of all terrestrial reptile species. Variation in body size was predicted by differences in the length of activity season, while we found no effects of environmental temperature per se. Females experiencing relatively short activity season mature at a larger size and remain larger on average than females in populations with relatively long activity seasons. Interpopulation variation in fecundity was largely explained by mean body size of females and reproductive mode, with viviparous populations having larger clutch size than oviparous populations. Finally, body size‐fecundity relationship differs between viviparous and oviparous populations, with relatively lower reproductive investment for a given body size in oviparous populations. While the phylogenetic signal was weak overall, the patterns of variation showed spatial effects, perhaps reflecting genetic divergence or geographic variation in additional biotic and abiotic factors. Our findings emphasize that time constraints imposed by the environment rather than ambient temperature play a major role in shaping life histories in the common lizard. This might be attributed to the fact that lizards can attain their preferred body temperature via behavioral thermoregulation across different thermal environments. Length of activity season, defining the maximum time available for lizards to maintain optimal performance, is thus the main environmental factor constraining growth rate and annual rates of mortality. Our results suggest that this factor may partly explain variation in the extent to which different taxa follow ecogeographic rules.