Upslope movements and large scale expansions: the taxonomy and biogeography of the Coenonympha arcania –C. d arwiniana –C. gardetta butterfly species complex

Sibling species groups are suitable models for the understanding of inter‐ and intraspecific processes in taxonomy and biogeography. We analysed 262 individuals from the Alps of the Coenonympha arcania/gardetta species complex by allozyme electrophoresis. These taxa showed high variance amongst populations (F_ST: 0.391) and strong intertaxon genetic differentiation (F_CT: 0.376). Although morphologically similar, Coenonympha gardetta and Coenonympha arcania clearly differ in their genetic characteristics; the morphologically intermediate taxa Coenonympha darwiniana darwiniana and Coenonympha darwiniana macromma are genetically well distinguished from each other and the two other taxa. Coenonympha arcania and C. d. macromma most probably share a common ancestor and evolved by cladogenesis, whereas the taxonomic situation of C. d. darwiniana is still unresolved: This taxon might be the result of hybridization between C. arcania and C. gardetta or it might have a common ancestor together with C. gardetta. We suggest species rank for all four taxa. The distribution of genetic diversity of these populations and the differentiation amongst populations suggest rather different biogeographical scenarios: C. arcania most probably is of Mediterranean origin with postglacial range expansion northwards; C. gardetta survived the last ice age in peripheral refugia of the Alps and has spread all over this high mountain system in the postglacial; C. darwiniana and C. macromma survived the Würm in geographic proximity to their actual distribution areas and only have performed moderate uphill translocations during postglacial warming. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 890–904.     

High-elevation plants have reduced plasticity in flowering time in response to warming compared to low-elevation congeners

Global warming has caused shifts in the flowering time of many plant species. In alpine regions the temperature rise has been especially pronounced and together with decreasing winter precipitation has led to earlier snowmelt. The close association between time of snowmelt and plant growth at high elevations makes climate change for alpine plants particularly threatening. Here we transplanted eleven congeneric pairs of high- and low-elevation herbaceous species to common gardens differing c. 800 m in elevation, and c. 4 °C in mean growing season temperature to test whether reproductive phenologies of high- and low-elevation plants differ in their respective responses to temperature. Results indicate that high-elevation plants were less plastic in response to transplantation than their low-elevation congeners as the onsets of phenophases on average shifted 7 days less than in low-elevation plants. Plasticity of phenophase durations was overall weaker than that of phenophase onsets, and slightly stronger in high-elevation species compared to low-elevation congeners. We suggest that weaker plasticity in the onsets of early stages of reproductive phenology of high-elevation plants is related to spring frost, which constitutes a strong selective agent against early loss of winter hardiness. Some of the plastic responses of both low- and high-elevation species might potentially be adaptive under predicted climate change. However, the observed plasticity can be largely explained as a passive response to temperature and not as the result of natural selection in heterogeneous environments. The strong temperature-sensitivity of low-elevation species might promote their upward range expansion, but only to a certain threshold after which it becomes limited by the short growing season.     

Speciation with gene flow: Evidence from a complex of alpine butterflies (Coenonympha,Satyridae)

Until complete reproductive isolation is achieved, the extent of differentiation between two diverging lineages is the result of a dynamic equilibrium between genetic isolation and mixing. This is especially true for hybrid taxa, for which the degree of isolation in regard to their parental species is decisive in their capacity to rise as a new and stable entity. In this work, we explored the past and current patterns of hybridization and divergence within a complex of closely related butterflies in the genus Coenonympha in which two alpine species, C. darwiniana and C. macromma, have been shown to result from hybridization between the also alpine C. gardetta and the lowland C. arcania. By testing alternative scenarios of divergence among species, we show that gene flow has been uninterrupted throughout the speciation process, although leading to different degrees of current genetic isolation between species in contact zones depending on the pair considered. Nonetheless, at broader geographic scale, analyses reveal a clear genetic differentiation between hybrid lineages and their parental species, pointing out to an advanced stage of the hybrid speciation process. Finally, the positive correlation observed between ecological divergence and genetic isolation among these butterflies suggests a potential role for ecological drivers during their speciation processes.     

How Useful is Fluctuating Asymmetry in Conservation Biology: Asymmetry in Rare and Abundant Coenonympha Butterflies

It has been suggested that minor, fluctuating differences in size of bilateral traits could validly indicate individual differences in developmental stability. One plausible reason for instability to occur could be lowered population size, which has been suggested to increase fluctuating asymmetry due to inbreeding, for example. We measured seven wing asymmetries of three Coenonympha butterfly species in central Sweden. One species is abundant (nobreak C. pamphilus), one rather common (C. arcania), and one rare (C. hero). We expected that if fluctuating asymmetry is a reliable indicator of population quality and thus a useful tool for conservation purposes, the most abundant species should show lowest asymmetry and the most endangered, the highest. Contrary to our expectations, the highest wing asymmetry was found in the relatively common species C. arcania and the most abundant and rare species did not show significant differences in levels of wing asymmetry. Our results obtained from three Coenonympha species hence suggest that the use of fluctuating asymmetry as an indicator of population conservation status may be misleading. Possible increase in asymmetry of small and/or isolated populations of butterflies may be masked by local differences in environmental conditions that could have high impact on bilateral development as well.     

Adaptability to elevated temperature and nitrogen addition is greater in a high-elevation population than in a low-elevation population of Hippophae rhamnoides

Hippophae rhamnoides L. is a broadleaf deciduous woody shrub occurring in southwest China, where it has been widely used in ecological restoration. In this study we investigated growth and physiological responses of 2-year-old healthy seedlings to elevated temperature, nitrogen (N) addition and their combination in two contrasting populations from high and low elevations. In closed-top chamber experiments, two populations were subjected to two temperature conditions (ambient temperature and temperature elevated by 2.2 ± 0.2°C) and two N levels (0 and 25 g N m⁻² a⁻¹). Compared with the control, increases in total leaf area (TLA), total chlorophyll content (TC), light-saturated photosynthetic rate (P _max), guaiacol peroxidase activity (POD), catalase activity (CAT) and carbon isotope composition (δ¹³C) were greater in the high-elevation population than in the low-elevation population under elevated temperature. On the other hand, decreases in root and shoot biomass ratio (RS), TC, P _max, light saturation point (L _SP), light compensation point (L _CP), superoxide dismutase (SOD), POD, CAT and δ¹³C were lower in the high-elevation population than in the low-elevation population under N addition. Moreover, the combination of elevated temperature and N addition decreased RS, P _max, apparent quantum efficiency (Φ), SOD, POD and δ¹³C significantly more in the low-elevation population than in the high-elevation population. These results demonstrated that there are different adaptive strategies among H. rhamnoides populations, the high-elevation population exhibiting higher adaptability to elevated temperature and N addition than the low-elevation population.     

Seed dispersal of a fleshy-fruited invasive shrub is affected by changes in the frugivorous bird assemblage along an elevational gradient

Seed dispersal by birds constitutes an essential mechanism for ornithochorous exotic plants to successfully invade a new system. New biotic associations with native birds might facilitate the upward spread of exotic plants from the foothills into the high mountains. However, environmental changes associated with elevation are known to drive changes in bird assemblages, and it is not clear how elevation changes impact the seed dispersal service of ornithochorous invaders. We evaluated changes in frugivorous bird assemblages of one of the exotic shrubs (Cotoneaster franchetii, Rosaceae) with the broadest elevation range among woody invaders in the Córdoba Mountains (Argentina). We quantified frugivory interactions (including absolute and proportional fruit consumption by seed dispersers, pulp consumers, and seed predators) using 4-h observations of focal C. franchetii shrubs distributed across low-elevation, mid-elevation, and high-elevation sites (700, 1100, and 1800 m a.s.l., respectively; 15 individuals per elevational band and one site per elevation). Seed disperser richness was highest at the low- and mid-elevation sites (three species vs. one at the high-elevation site), but proportional and absolute fruit consumption of C. franchetii was highest at the high-elevation site (39.1%, 88 seeds at high-elevation and 7.7%, 20 seeds at low-elevation). The Chiguanco Thrush (Turdus chiguanco, Turdidae) was the only seed disperser species found at the highest elevation site. Fruit consumption by seed dispersers was positively related to their abundance and elevation. In a high mountain system, a single abundant generalist seed disperser, rather than a high richness of seed disperser species, can uphold an effective dispersal service for an invasive ornithochorous shrub. This pattern may facilitate the spread of such plants across higher elevational ranges, thereby promoting the invasion of other exotic ornithochorous plants into upper elevations.     

Elevational variation in adult body size and growth rate but not in metabolic rate in the tree weta Hemideina crassidens

Populations of the same species inhabiting distinct localities experience different ecological and climatic pressures that might result in differentiation in traits, particularly those related to temperature. We compared metabolic rate (and its thermal sensitivity), growth rate, and body size among nine high- and low-elevation populations of the Wellington tree weta, Hemideina crassidens, distributed from 9 to 1171 m a.s.l across New Zealand. Our results did not indicate elevational compensation in metabolic rates (metabolic cold adaptation). Cold acclimation decreased metabolic rate compared to warm-acclimated individuals from both high- and low-elevation populations. However, we did find countergradient variation in growth rates, with individuals from high-elevation populations growing faster and to a larger final size than individuals from low-elevation populations. Females grew faster to a larger size than males, although as adults their metabolic rates did not differ significantly. The combined physiological and morphological data suggest that high-elevation individuals grow quickly and achieve larger size while maintaining metabolic rates at levels not significantly different from low-elevation individuals. Thus, morphological differentiation among tree weta populations, in concert with genetic variation, might provide the material required for adaptation to changing conditions.     

Transferring soils from high- to low-elevation forests increases nitrogen cycling rates: climate change implications

We assessed the potential impact of global warming resulting from a doubling of preindustrial atmospheric CO₂ on soil net N transformations by transferring intact soil cores (0–15 cm) from a high-elevation old-growth forest to a forest about 800 m lower in elevation in the central Oregon Cascade Mountains, USA. The lower elevation site had mean annual air and soil (10-cm mineral soil depth) temperatures about 2.4 and 3.9 °C higher than the high-elevation site, respectively. Annual rates of soil net N mineralization and nitrification more than doubled in soil transferred to the low-elevation site (17.2–36.0 kg N ha^–1 and 5.0–10.7 kg NO₃^––N ha^–1, respectively). Leaching of inorganic N from the surface soil (in the absence of plant uptake) also increased. The reciprocal treatment (transferring soil cores from the low- to the high-elevation site) resulted in decreases of about 70, 80, and 65% in annual rates of net N mineralization, nitrification, and inorganic N leaching, respectively. Laboratory incubations of soils under conditions of similar temperature and soil water potential suggest that the quality of soil organic matter is higher at the high-elevation site. Similar in situ rates of soil net N transformations between the two sites occurred because the lower temperature counteracts the effects of greater substrate quantity and quality at the high elevation site. Our results support the hypothesis that high-elevation, old-growth forest soils in the central Cascades have higher C and N storage than their low-elevation analogues primarily because low temperatures limit net C and N mineralization rates at higher elevations.     

Hybridization promotes speciation in Coenonympha butterflies

Hybridization has become a central element in theories of animal evolution during the last decade. New methods in population genomics and statistical model testing now allow the disentangling of the complexity that hybridization brings into key evolutionary processes such as local adaptation, colonization of new environments, species diversification and extinction. We evaluated the consequences of hybridization in a complex of three alpine butterflies in the genus Coenonympha, by combining morphological, genetic and ecological analyses. A series of approximate Bayesian computation procedures based on a large SNP data set strongly suggest that the Darwin's Heath (Coenonympha darwiniana) originated through hybridization between the Pearly Heath (Coenonympha arcania) and the Alpine Heath (Coenonympha gardetta) with different parental contributions. As a result of hybridization, the Darwin's Heath presents an intermediate morphology between the parental species, while its climatic niche seems more similar to the Alpine Heath. Our results also reveal a substantial genetic and morphologic differentiation between the two geographically disjoint Darwin's Heath lineages leading us to propose the splitting of this taxon into two different species.     

Growth response of Sabina tibetica to climate factors along an elevation gradient in south Tibet

We examine the climate significance in tree-ring chronologies retrieved from Sabina tibetica Kom. (Tibetan juniper) at two sites ranging in elevation from 4124 to 4693 m above sea level (a.s.l.) in the Namling region, south Tibet. The study region is under the control of semi-arid plateau temperate climate. The samples were grouped into high- and low-elevation classes and standard ring-width chronologies for both classes were developed. Statistical analysis revealed a decreasing growth rate yet increasing chronology reliability with increasing elevation. Overall, correlation analyses showed that radial growth in S. tibetica at the study sites was controlled by similar climatic factors, regardless of elevation; these factors comprised early winter (November) and early summer (May–June) temperatures as well as annual precipitation (July–June). Slight differences in the correlation between tree growth along the elevation gradient and climate variables were examined. The correlations with early winter temperature varied from significantly positive at the low-elevation site to weakly positive at the high-elevation site, whereas the correlations between radial growth and early summer temperature increased from weakly negative at the low-elevation sites to strongly negative at the high-elevation sites. The abundant precipitation through the year may have masked variations in tree growth on different elevation aspects. Our results will aid future dendroclimatological studies of Namling tree rings in south Tibet and demonstrate the potential of S. tibetica Kom. for improving our understanding of environmental impacts on tree growth.     

Interannual growth response of Norway spruce to climate along an altitudinal gradient in the Tatra Mountains, Poland

Ring-width chronologies of Picea abies (L.) Karst. from ten sites in the Tatra Mountains, Poland, were developed to explore growth/climate responses in stands along an altitudinal gradient ranging from 839 to 1468 m a.s.l. There were positive relationships between current-year radial growth and mean monthly temperatures in March, April, June and July, but with increasing elevation, the strength of this correlation declined for March–April and increased for June–July temperatures. The mean monthly temperature in October of the previous year positively influenced radial growth of trees at all sites. Lower mean temperatures in January negatively affected growth of trees at the high-elevation sites. Trees at the low-elevation sites responded positively to a warm early spring, whereas trees at the high-elevation sites showed positive growth responses to higher summer temperatures. Growth of trees at the high-elevation sites was better explained by the temperature regime than was growth at the lower-elevation sites. Therefore, it is likely that these sites may be particularly sensitive to potential effects of temperature change.     

Plant transpiration at high elevations: Theory,field measurements,and comparisons with desert plants

Summary The influence of elevational changes on plant transpiration was evaluated using leaf energy balance equations and well-known elevational changes in the physical parameters that influence water vapor diffusion. Simulated transpirational fluxes for large leaves with low and high stomatal resistances to water vapor diffusion were compared to small leaves with identical stomatal resistances at elevations ranging from sea level to 4 km. The specific influence of various air temperature lapse rates was also tested. Validation of the simulated results was accomplished by comparing actual field measurements taken at a low elevation (300 m) desert site with similar measurements for a high elevation (2,560 m) mountain research site. Close agreement was observed between predicted and measured values of transpiration for the environmental and leaf parameters tested.Substantial increases in solar irradiation and the diffusion coefficient for water vapor in air (D _wv) occurred with increasing elevation, while air and leaf temperatures, the water vapor concentration difference between the leaf and air, longwave irradiation, and the thermal conductivity coefficient for heat in air decreased with increasing elevation. These changes resulted in temperatures for sunlit leaves that were further above air temperature at higher elevations, especially for large leaves. For large leaves with low stomatal resistances, transpirational fluxes for low-elevation desert plants were close to those predicted for high-elevation plants even though the sunlit leaf temperatures of these mountain plants were over 10°C cooler. Simulating conditions with a low air temperature lapse rate (0.003° C m^-1 and 0.004° C m^-1) resulted in predicted transpirational fluxes that were greater than those calculated for the desert site. Transpiration for smaller leaves decreased with elevation for all lapse rates tested (0.003° C m^-1 to 0.010° C m^-1). However, transpirational fluxes at higher elevations were considerably greater than expected for all leaves, especially larger leaves, due to the strong influence of increased solar heating and a greater D _wv. These results are discussed in terms of similarities in leaf structure and plant habit observed among low-elevation desert plants and high-elevation alpine and subalpine plants.     

不同高程短尖苔草对水位变化的生长及繁殖响应

在淡水湿地生态系统中,水位通常是制约植被生长和繁殖动态的关键因素,进而对物种组成、群落演替和植被分布格局产生决定性影响。无性繁殖是洞庭湖湿地克隆植物适应环境胁迫的重要策略之一,以洞庭湖湿地典型克隆植物-短尖苔草(Carex brevicuspis C.B.Clarke)为对象,研究了不同分布高程(23.7 m和25.8 m)的植物对水位变化(0 cm,-15 cm,-30 cm)的生长和繁殖特征响应。结果表明:水位变化对不同分布高程分布短尖苔草的生长和克隆繁殖特征均产生显著影响(P0.05)。对高程区的短尖苔草而言,克隆繁殖特征如分株数、分株总生物量、芽数和芽生物量随水位的降低而增加,而对生长特征(株高及总生物量)无显著影响(P0.05),表明适当干旱有利于高程区苔草的克隆繁殖。对于低程区分布短尖苔草而言,水位变化对其生长特征有显著影响(P0.05),如株高和总生物量随着水位的降低而增加;分株数和总芽生物量等克隆繁殖特征则随水位的降低而减少,而水位对低程区短尖苔草的分株总生物量和总芽数影响不显著(P0.05)。因此,短尖苔草的克隆繁殖特征除受到水位的影响外,还受其分布高程的影响。可见,同一种短尖苔草因长期适应于不同生境而对相同的环境胁迫表现出了不同的生长繁殖策略,     

Age structure and body size of the Chuanxi Tree Frog Hyla annectans chuanxiensis from two different elevations in Sichuan (China)

Age, body size, and growth patterns in the subtropical anuran Hyla annectans chuanxiensis from high (Dengchigou Protection Station) and low (Lingguan Town) elevations in Baoxing County of Sichuan province (China) were described using skeletochronology. Females were significantly older than males at the low-elevation site, but there was no significant difference between the sexes at the high-elevation site. Age at sexual maturity of both males and females was 2 years at the high-elevation site, whereas males matured at 1 year and females at 2 years at the low-elevation site. Males and females from the low-elevation population reached a maximum age of 3 and 4 years, respectively, whereas males and females from the high-elevation population reached a maximum age of 4 and 5 years, respectively. At both sites, females were significantly larger than males. Females and males from the high-elevation population were larger than individuals from the low-elevation population. When the effect of age was controlled, the differences in body size of the two populations were significant only for females. Von Bertalanffy growth curves indicated that the growth rates in males was greater than in females in both populations. They also showed that the growth of both sexes slowed at an earlier age in the low-elevation population than in the high-elevation population. The findings suggest that age is a major factor underlying body size patterns for both sexes, but that the elevation of the locality affects the body size of females.     

Assessing the effectiveness of protected areas for conserving range-restricted rain forest butterflies in Sabah,Borneo

Rain forests on Borneo support exceptional concentrations of endemic insect biodiversity, but many of these forest-dependent species are threatened by land-use change. Totally protected areas (TPAs) of forest are key for conserving biodiversity, and we examined the effectiveness of the current TPA network for conserving range-restricted butterflies in Sabah (Malaysian Borneo). We found that mean diurnal temperature range and precipitation of the wettest quarter of the year were the most important predictors of butterfly distributions (N = 77 range-restricted species), and that species richness increased with elevation and aboveground forest carbon. On average across all species, TPAs were effective at conserving ~43% of species’ ranges, but encompassed only ~40% of areas with high species richness (i.e., containing at least 50% of our study species). The TPA network also included only 33%–40% of areas identified as high priority for conserving range-restricted species, as determined by a systematic conservation prioritization analysis. Hence, the current TPA network is reasonably effective at conserving range-restricted butterflies, although considerable areas of high species richness (6,565 km²) and high conservation priority (11,152–12,531 km²) are not currently protected. Sabah's remaining forests, and the range-restricted species they support, are under continued threat from agricultural expansion and urban development, and our study highlights important areas of rain forest that require enhanced protection.     

Role of morphological variables of the visitor butterfly species in relation to their foraging behaviour on Lantana camara: Implication for conservation

The study of foraging behaviour of butterflies has been an important focus among the lepidopterists for years. Although established as invasive weed plant, the role Lantana camara as an important host plant as well as a food plant for the butterfly species is now well-known. The present study aims to interpret the role of morphological variables of the visitor butterflies in relation to their foraging behaviour on Lantana camara. Butterflies with longer proboscis were more efficient in foraging on flowers of Lantana camara than the butterflies with shorter ones, when the species containing proboscis same as or longer than their body length were excluded. Longer relative proboscis length (RPL) have selective advantage for foraging over Lantana camara up to a certain point (RPL = 0.881) and after that larger relative proboscis length often obstructs foraging behaviour as the handling time increases and these butterflies face more resistance against incoming nectar than the others.The residuals (body weight-wing span) also act as important factor.The handling time of the butterflies on Lantana camara shows a negative relationship with the residuals. The findings suggests that in case of Lantana camara as a nectaring plant butterfly species with longer proboscis have selective advantage for exploitation of the resource than the species with shorter ones and plantation of Lantana camara may be useful for conserving the long tongued butterfly species.     

Rewiring of interactions in a changing environment: nettle-feeding butterflies and their parasitoids

Climate and land use change can alter the incidence and strength of biotic interactions, with important effects on the distribution, abundance and function of species. To assess the importance of these effects and their dynamics, studies quantifying how biotic interactions change in space and time are needed. We studied interactions between nettle-feeding butterflies and their shared natural enemies (parasitoids) locally and across 500 km latitudinal gradient in Sweden. We also examined the potential impact of the range-expansion of the butterfly Araschnia levana on resident butterflies via shared parasitoids, by studying how parasitism in resident butterflies covaries with the presence or absence of the newly-established species. We collected 6777 larvae of four nettle-feeding butterfly species (Aglais urticae, Aglais io, Ar. levana and Vanessa atalanta), over two years, at 19 sites distributed along the gradient. We documented the parasitoid complex for each butterfly species and measured their overlap, and analysed how parasitism rates were affected by butterfly species assemblage, variations in abundance, time, and the arrival of Ar. levana. Parasitoids caused high mortality, with substantial overlap in the complex of parasitoids associated with the four host butterflies. Levels of parasitism differed significantly among butterflies and were influenced by the local butterfly species assemblage. Our results also suggest that parasitism in resident butterflies is elevated at sites where Ar. levana has been established for a longer period. In our study system, variations in butterfly species assemblages were associated in a predictable way with substantial variations in rates of parasitism. This relationship is likely to affect the dynamics of the butterfly host species, and potentially cascade to the larger number of species with which they interact. These results highlight the importance of indirect interactions and their potential to reorganise ecological communities, especially in the context of shifts in species distributions in a warmer world.     

Age structure and body size of the Chuanxi Tree Frog Hyla annectans chuanxiensis from two different elevations in Sichuan (China)

Age, body size, and growth patterns in the subtropical anuran Hyla annectans chuanxiensis from high (Dengchigou Protection Station) and low (Lingguan Town) elevations in Baoxing County of Sichuan province (China) were described using skeletochronology. Females were significantly older than males at the low-elevation site, but there was no significant difference between the sexes at the high-elevation site. Age at sexual maturity of both males and females was 2 years at the high-elevation site, whereas males matured at 1 year and females at 2 years at the low-elevation site. Males and females from the low-elevation population reached a maximum age of 3 and 4 years, respectively, whereas males and females from the high-elevation population reached a maximum age of 4 and 5 years, respectively. At both sites, females were significantly larger than males. Females and males from the high-elevation population were larger than individuals from the low-elevation population. When the effect of age was controlled, the differences in body size of the two populations were significant only for females. Von Bertalanffy growth curves indicated that the growth rates in males was greater than in females in both populations. They also showed that the growth of both sexes slowed at an earlier age in the low-elevation population than in the high-elevation population. The findings suggest that age is a major factor underlying body size patterns for both sexes, but that the elevation of the locality affects the body size of females.     

Elevational isolation of red fox populations in the Greater Yellowstone Ecosystem

Foxes in the Greater Yellowstone Ecosystem are reported to show high frequencies of blonde and gray coat colors. A survey of park sighting records showed that the frequency of the novel coat colors significantly increases at elevations greater than 2300 m, suggesting some form of elevational isolation. We evaluated the degree of genetic separation between the high-elevation foxes (>2300 m) and contiguous populations of foxes at mid-elevations (1600–2300m). Low-elevation (>1600 m) foxes from North Dakota, >1000 km straight line distance from our populations, were used as a control group. We genotyped 15 high-elevation, 15 mid-elevation, and 10 low-elevation foxes at 10 microsatellite loci each. Heterozygosity was significantly lower in both the high-elevation and mid-elevation populations compared to the low-elevation foxes. The genetic differentiation was significantly greater between the high-elevation and mid-elevation foxes than between the mid-elevation and low-elevation foxes. Similarly, estimates of R_ST and F_ST suggest less gene flow occurs between the contiguous high- and mid-elevation fox populations than between the mid- and low-elevation fox populations separated by > 1000 km. The assignment test further supports this hypothesis. Although further work is needed, we suggest that the high-elevation foxes are remnant populations from the Wisconsin glaciation and should be managed as a unique population.     

Life-history traits of two Mediterranean lizard populations: a possible example of countergradient covariation

The trade-off between clutch and offspring size, which is a central topic in life-history research, is shaped by natural selection to maximize the number of surviving offspring, but it also depends on the resources available for reproduction. Conspecific populations living in different environments may differ in adult body size, clutch mass, clutch size, offspring size, and/or post-natal growth rates, due either to phenotypic plasticity or to local adaptation. Here, we compare these traits and their relationships between two populations of the lizard Psammodromus algirus separated by a 600-m altitudinal gradient. We used a common garden design to control incubation temperature and food availability, with two different feeding treatments. Females were larger at the high-elevation site. Although SVL-adjusted clutch mass did not differ between populations, high-elevation females laid more but smaller eggs than low-elevation ones. Hatchlings were larger at lower elevation. Our common garden experiment revealed that low-elevation hatchlings grew faster than high-elevation hatchlings under both feeding treatments. However, higher food availability at higher altitude allows high-elevation lizards to grow faster and attain larger adult sizes, especially in the case of females. The two key adaptations of low-elevation lizards, large eggs and hatchlings and the ability to grow rapidly after hatching, are likely to enhance survival in low-productivity Mediterranean lowlands. Our data support the hypothesis that the reproductive strategies of these populations provide an example of countergradient variation, because the genotypes that encode for fast growth and large body size occurred in low food availability habitats where juveniles grew slowly and attained small adult sizes.