High-elevation Populations Research Articles

The roles of acclimation and behaviour in buffering climate change impacts along elevational gradients.

The vulnerability of species to climate change is jointly influenced by geographic phenotypic variation, acclimation and behavioural thermoregulation. The importance of interactions between these factors, however, remains poorly understood. We demonstrate how advances in mechanistic niche modelling can be used to integrate and assess the influence of these sources of uncertainty in forecasts of climate change impacts. We explored geographic variation in thermal tolerance (i.e. maximum and minimum thermal limits) and its potential for acclimation in juvenile European common frogs Rana temporaria along elevational gradients. Furthermore, we employed a mechanistic niche model (NicheMapR) to assess the relative contributions of phenotypic variation, acclimation and thermoregulation in determining the impacts of climate change on thermal safety margins and activity windows. Our analyses revealed that high-elevation populations had slightly wider tolerance ranges driven by increases in heat tolerance but lower potential for acclimation. Plausibly, wider thermal fluctuations at high elevations favour more tolerant but less plastic phenotypes, thus reducing the risk of encountering stressful temperatures during unpredictable extreme events. Biophysical models of thermal exposure indicated that observed phenotypic and plastic differences provide limited protection from changing climates. Indeed, the risk of reaching body temperatures beyond the species' thermal tolerance range was similar across elevations. In contrast, the ability to seek cooler retreat sites through behavioural adjustments played an essential role in buffering populations from thermal extremes predicted under climate change. Predicted climate change also altered current activity windows, but high-elevation populations were predicted to remain more temporally constrained than lowland populations. Our results demonstrate that elevational variation in thermal tolerances and acclimation capacity might be insufficient to buffer temperate amphibians from predicted climate change; instead, behavioural thermoregulation may be the only effective mechanism to avoid thermal stress under future climates.

Untangling cryptic diversity in the High Andes: Revision of the Scytalopus [magellanicus] complex (Rhinocryptidae) in Peru reveals three new species

AbstractTropical mountains feature marked species turnover along elevational gradients and across complex topography, resulting in great concentrations of avian biodiversity. In these landscapes, particularly among morphologically conserved and difficult to observe avian groups, species limits still require clarification. One such lineage is Scytalopus tapaculos, which are among the morphologically most conserved birds. Attention to their distinctive vocal repertoires and phylogenetic relationships has resulted in a proliferation of newly identified species, many of which are restricted range endemics. Here, we present a revised taxonomy and identify species limits among high-elevation populations of Scytalopus tapaculos inhabiting the Peruvian Andes. We employ an integrated framework using a combination of vocal information, mitochondrial DNA sequences, and appearance, gathered from our own fieldwork over the past 40 yr and supplemented with community-shared birdsong archives and museum specimens. We describe 3 new species endemic to Peru. Within all 3 of these species there is genetic differentiation, which in 2 species is mirrored by subtle geographic plumage and vocal variation. In a fourth species, Scytalopus schulenbergi, we document deep genetic divergence and plumage differences despite overall vocal similarity. We further propose that an extralimital taxon, Scytalopus opacus androstictus, be elevated to species rank, based on a diagnostic vocal character. Our results demonstrate that basic exploration and descriptive work using diverse data sources continues to identify new species of birds, particularly in tropical environs.

Variation in the seasonal germination niche across an elevational gradient: the role of germination cueing in current and future climates.

The timing of germination has profound impacts on fitness, population dynamics, and species ranges. Many plants have evolved responses to seasonal environmental cues to time germination with favorable conditions; these responses interact with temporal variation in local climate to drive the seasonal climate niche and may reflect local adaptation. Here, we examined germination responses to temperature cues in Streptanthus tortuosus populations across an elevational gradient. Using common garden experiments, we evaluated differences among populations in response to cold stratification (chilling) and germination temperature and related them to observed germination phenology in the field. We then explored how these responses relate to past climate at each site and the implications of those patterns under future climate change. Populations from high elevations had stronger stratification requirements for germination and narrower temperature ranges for germination without stratification. Differences in germination responses corresponded with elevation and variability in seasonal temperature and precipitation across populations. Further, they corresponded with germination phenology in the field; low-elevation populations germinated in the fall without chilling, whereas high-elevation populations germinated after winter chilling and snowmelt in spring and summer. Climate-change forecasts indicate increasing temperatures and decreasing snowpack, which will likely alter germination cues and timing, particularly for high-elevation populations. The seasonal germination niche for S. tortuosus is highly influenced by temperature and varies across the elevational gradient. Climate change will likely affect germination timing, which may cascade to influence trait expression, fitness, and population persistence.

Integrative taxonomic analysis reveals a new species of Leptobrachium (Anura: Megophryidae) from north-eastern Cambodia and central Vietnam

ABSTRACT Species boundaries within the red-eyed Leptobrachium of southern Indochina have been uncertain. Leptobrachium pullum and L. mouhoti from upper and lower elevations, respectively, of the Langbian Plateau of southern Vietnam and eastern Cambodia differ in body size but have relatively low interspecific mitochondrial DNA divergence, leading to speculation that these might represent a single species with an elevational cline in body size. The recent discovery of an allopatric high-elevation population of red-eyed Leptobrachium on the Kon Tum Plateau (= Central Highlands) of north-eastern Cambodia and central Vietnam has been referred to both species, and to a putatively undescribed species. We examine variation in morphology of adults and tadpoles, mitochondrial DNA, 11 nuclear genes and advertisement calls, and show corroborating lines of evidence for the existence of three species of red-eyed Leptobrachium in southern Indochina. Although the three species are reciprocally monophyletic in mitochondrial DNA, their shallow mitochondrial DNA divergences are not mirrored by morphology, advertisement calls, or – in part – nuclear DNA, and probably reflect past mitochondrial introgression rather than recent speciation. The Central Highlands taxon is described herein as a new species. http://www.zoobank.org/urn:lsid:zoobank.org:pub:CE6650AF-D9FB-40F4-8A2E-9B4E23AAC205

Genetic structure of Australian glass shrimp, Paratya australiensis, in relation to altitude.

Paratya australiensis Kemp (Decapoda: Atyidae) is a widely distributed freshwater shrimp in eastern Australia. The species has been considered as an important stream organism for studying genetics, dispersal, biology, behaviour and evolution in atyids and is a major food source for stream dwelling fishes. Paratya australiensis is a cryptic species complex consisting of nine highly divergent mitochondrial DNA lineages. Previous studies in southeast Queensland showed that “lineage 4” favours upstream sites at higher altitudes, with cooler water temperatures. This study aims to identify putative selection and population structure between high elevation and low elevation populations of this lineage at relatively small spatial scales. Sample localities were selected from three streams: Booloumba Creek, Broken Bridge Creek and Obi Obi Creek in the Conondale Range, southeast Queensland. Six sample localities, consisting of 142 individuals in total were sequenced using double digest Restriction Site Associated DNA-sequencing (ddRAD-seq) technique. Among the 142 individuals, 131 individuals shared 213 loci. Outlier analysis on 213 loci showed that 27 loci were putatively under selection between high elevation and low elevation populations. Outlier analysis on individual streams was also done to test for parallel patterns of adaptation, but there was no evidence of a parallel pattern. Population structure was observed using both the 27 outliers and 186 neutral loci and revealed similar population structure in both cases. Therefore, we cannot differentiate between selection and drift here. The highest genetic differentiation was observed between high elevation and low elevation populations of Booloumba Creek, with small levels of differentiation in the other two streams.

Do different rates of gene flow underlie variation in phenotypic and phenological clines in a montane grasshopper community?

Species responses to environmental change are likely to depend on existing genetic and phenotypic variation, as well as evolutionary potential. A key challenge is to determine whether gene flow might facilitate or impede genomic divergence among populations responding to environmental change, and if emergent phenotypic variation is dependent on gene flow rates. A general expectation is that patterns of genetic differentiation in a set of codistributed species reflect differences in dispersal ability. In less dispersive species, we predict greater genetic divergence and reduced gene flow. This could lead to covariation in life‐history traits due to local adaptation, although plasticity or drift could mirror these patterns. We compare genome‐wide patterns of genetic structure in four phenotypically variable grasshopper species along a steep elevation gradient near Boulder, Colorado, and test the hypothesis that genomic differentiation is greater in short‐winged grasshopper species, and statistically associated with variation in growth, reproductive, and physiological traits along this gradient. In addition, we estimate rates of gene flow under competing demographic models, as well as potential gene flow through surveys of phenological overlap among populations within a species. All species exhibit genetic structure along the elevation gradient and limited gene flow. The most pronounced genetic divergence appears in short‐winged (less dispersive) species, which also exhibit less phenological overlap among populations. A high‐elevation population of the most widespread species, Melanoplus sanguinipes, appears to be a sink population derived from low elevation populations. While dispersal ability has a clear connection to the genetic structure in different species, genetic distance does not predict growth, reproductive, or physiological trait variation in any species, requiring further investigation to clearly link phenotypic divergence to local adaptation.

Elevational differentiation in metabolic cold stress responses of an endemic mountain tree

The decline of mountain forests under global change is alarming and conservation is challenged by the need to assemble populations able to deal with the predicted environmental shifts. Assessing intraspecific differentiation in stress susceptibility of tree species along elevational gradients is crucial to identify adequate genetic sources for mountain forest restoration. Here, we assessed injury and metabolic responses across cold stress intensity gradients in low and high elevation populations of the endangered mountain tree Polylepis australis. We hypothesized that populations from high elevational origins will show weaker increases of injury and more pronounced metabolic responses with rising cold stress intensity than low elevation populations. The expected differentiation among elevational origins was not observed for cold stress injury, but for metabolic stress responses. Plants responded to cold with enhanced concentrations of sugars, organic acids, amines and specialized metabolites with freezing point depressing, cryo-protective and anti-oxidative properties. As predicted, these responses were more pronounced and partially increased more strongly with stress intensity in high than low elevation populations, indicating local adaptation to a higher frequency and intensity of cold events at high elevations. We discuss the power of metabolomics approaches in unravelling intraspecific differentiation in tree stress resistance across small geographic scales as well as implications for future research on the evolution of cross-resistance to multiple stressors and for forest restoration.

Decreased nest survival associated with low temperatures in a high-elevation population of Mountain Plover (Charadrius montanus)

Mountain Plovers (Charadrius montanus) are migratory shorebirds of conservation concern that breed on grasslands and xeric tablelands scattered along the western edge of the Great Plains. Previous research from populations breeding on lower-elevation sites in Colorado and Montana suggests nest survival increases in cooler, drier environmental conditions. However, no studies have estimated Mountain Plover nest survival on high-elevation habitats, which have distinctively different climate and nesting phenology; therefore, it is unclear if these general trends hold true for the species as a whole or are regionally specific. In this study, we monitored nests of a population of Mountain Plovers breeding at high elevation in South Park, Colorado, to study influences on daily nest survival as compared to those found in literature from lower-elevation breeding sites. In contrast to studies on lower-elevation sites where daily maximum temperatures limited nest survival, we found daily minimum temperature best predicted variation in daily nest survival in South Park; survival odds declined with decreasing temperature. These results suggest that negative effects of extreme temperatures (hot or cold) may be generalities that exist between locales but are potentially mediated through different mechanisms at varying temporal scales. Although we cannot definitively conclude from our study why minimum temperature is associated with lower nest survival, we suggest alterations in incubation behavior may be a plausible mechanism that warrants future study. Overall, our study demonstrates the importance of considering differences between weather and phenology among breeding locations when estimating nest survival effects.

Evolutionary constraint on low elevation range expansion: Defense-abiotic stress-tolerance trade-off in crosses of the ecological model Boechera stricta.

Most transplant experiments across species geographic range boundaries indicate that adaptation to stressful environments outside the range is often constrained. However, the mechanisms of these constraints remain poorly understood. We used extended generation crosses from diverged high and low elevation populations. In experiments across low elevation range boundaries, there was selection on the parental lines for abiotic stress‐tolerance and resistance to herbivores. However, in support of a defense‐tolerance trade‐off, extended generation crosses showed nonindependent segregation of these traits in the laboratory across a drought‐stress gradient and in the field across the low elevation range boundary. Genotypic variation in a marker from a region of the genome containing a candidate gene (MYC2) was associated with change in the genetic trade‐off. Thus, using crosses and forward genetics, we found experimental genetic and molecular evidence for a pleiotropic trade‐off that could constrain the evolution of range expansion.

Evidence of phenotypic correlation between exploration activity and resting metabolic rate among populations across an elevation gradient in a small rodent species

Behavior and metabolism are frontline reactions to environmental challenges that can covary in their response through at least two mechanisms. First, natural selection can generate correlation in phenotype among distinct populations if they are exposed to a common selective force. Thus, metabolism and behavior can exhibit phenotypic correlation among populations when responding (independently from each other) to co-varying selective forces. Second, because behavioral responses are energy-demanding, variation in energy acquisition or allocation among individuals of the same population can also generate, respectively, a positive or negative correlation within populations. To address this issue, we investigated among- and within-population (co)variations in exploration activity (EA) and resting metabolic rate (RMR) of adult common voles (Microtus arvalis) issued from four high-elevation populations (> 1400 m a.s.l.) and five low-elevation populations (< 520 m a.s.l.). Individuals were acclimatized for at least 1 month to the same laboratory conditions before being tested for EA and RMR. Voles from high-elevation populations were more explorative and they had higher RMR than their counterparts from low-elevation populations. The similar effects of elevation on EA and RMR accounted for a correlation of 0.28 (0.064; 0.658) between EA and RMR across low- and high-elevation populations. We found no evidence of a within-population correlation between EA and RMR. More work relying, for instance, on repeated sampling or experimental selection is nonetheless needed to confirm a lack of integration between metabolism and behavior at the individual level. Our results highlight the importance of co-varying selective forces in generating among-population phenotypic correlation between EA and RMR in this small rodent species.Significance statementThere is increasing interest at deciphering the sources of covariation between metabolism and behavioral traits. Phenotypic covariation can be observed among populations if metabolism and behavior are responding independently from each other to co-varying selective forces. Because behavioral responses are energy-demanding, variation in energy acquisition or allocation between individuals of the same population can also lead to, respectively, a positive or negative phenotypic correlation. In this study, we highlight the importance of co-varying selective forces in generating phenotypic correlation between metabolism and behavior across low- and high-elevation populations of a small rodent species. We found no evidence of a correlation within populations. More work relying, for instance, on repeated sampling or experimental selection is now needed to confirm a lack of integration between metabolism and behavior at the individual level.

Genetic variability and heritability of some morphological and physiological traits in Fagus orientalis Lipsky along an elevation gradient in Hyrcanian forests

Abstract The purpose of the present study was to evaluate the genetic variability and heritability of some morphological and physiological traits in Fagus orientalis Lipsky along an elevation gradient in northern forests of Iran. Beech leaves were sampled from southern and northern crown parts of healthy mature trees along an elevation gradient comprising sites situated at 700 m, 1,200 m and 1,700 m above the sea level. Our statistical analysis showed that the investigated traits differed significantly between the populations. The results indicated the lowest and the highest coefficients of variation for the high (1,700 m) and middle elevation populations (1,200 m) for leaf length, petiole length, leaf area, specific leaf area, dry weight, specific dry weight, leaf index and petiole index traits. With increasing elevation, mean leaf width, distance from leaf base to the leaf maximum width, dry weight and petiole index increased. The plasticity of leaf length, specific leaf area, specific dry weight, petiole index and petiole length peaked at middle elevation, and with increasing elevation, the plasticity of these traits declined. The distance from leaf base to the leaf maximum width had the highest coefficient of genetic (75.5%) and phenotypic (75.5%) variation. The heritability results showed that there were differences in all traits, and that the highest heritability was recorded for the distance from the leaf base to the leaf maximum width (99.95 %). The results suggest that the studied beech populations responded to the environmental changes by changing their leaf traits in different ways at different altitudes.

Lagging Adaptation to Climate Supersedes Local Adaptation to Herbivory in an Annual Monkeyflower.

While native populations are often adapted to historical biotic and abiotic conditions at their home site, populations from other locations in the range may be better adapted to current conditions due to changing climates or extreme conditions in a single year. We examine whether local populations of a widespread species maintain a relative advantage over distant populations that have evolved at sites better matching the current climate. Specifically, we grew lines derived from low- and high-elevation annual populations in California and Oregon of the common monkeyflower (Erythranthe guttata) and conducted phenotypic selection analyses in low- and high-elevation common gardens in Oregon to examine relative fitness and the traits mediating relative fitness. Californian low-elevation populations have the highest relative fitness at the low-elevation site, and Californian high-elevation populations have the highest relative fitness at the high-elevation site. Relative fitness differences are mediated by selection for properly timed transitions to flowering, with selection favoring more rapid growth rates at the low-elevation site and greater vegetative biomass prior to flowering at the high-elevation site. Fitness advantages for Californian plants occur despite incurring higher herbivory at both sites than the native Oregonian plants. Our findings suggest that a lag in adaptation causes maladaptation in extreme years that may be more prevalent in future climates, but local populations still have high growth rates and thus are not yet threatened.

Number of Pollinators and Its Visitation Rate Incur Different Intensities of Pollen Limitation in Meconopsis integrifolia

Pollen limitation commonly exists in the alpine species, yet, experimental estimates on the changeable trajectory of pollen limitation along elevational changes are rarely. We used field observations and supplemental hand pollination treatment to estimate the variation in pollen limitation among five different altitudes populations (from 3600 m.a.s.l. to 4400 m.a.s.l.) in Meconopsis integrifolia in two consecutive years. Correlation analysis was used to estimate which factor incurred the pollen limitation. Hand supplemental pollination indicated that pollen limitation occurred in the studied populations in both years. Pollen limitation was similar among low-elevation populations but doubled in the highest elevation population (4452 m.a.s.l.). The number of pollinators and visitation rate of pollinators were negatively related to the pollen limitation. Our results indicated that number of pollinators and visitation rate of pollinators were the main factors which incurred variation in pollen limitation of M. integrifolia among different altitudes.

Divergence in Glucosinolate Profiles between High- and Low-Elevation Populations of Arabidopsis halleri Correspond to Variation in Field Herbivory and Herbivore Behavioral Preferences.

Variation in local herbivore pressure along elevation gradients is predicted to drive variation in plant defense traits. Yet, the extent of intraspecific variation in defense investment along elevation gradients, and its effects on both herbivore preference and performance, remain relatively unexplored. Using populations of Arabidopsis halleri (Brassicaceae) occurring at different elevations in the Alps, we tested for associations between elevation, herbivore damage in the field, and constitutive chemical defense traits (glucosinolates) assayed under common-garden conditions. Additionally, we examined the feeding preferences and performance of a specialist herbivore, the butterfly Pieris brassicae, on plants from different elevations in the Alps. Although we found no effect of elevation on the overall levels of constitutive glucosinolates in leaves, relative amounts of indole glucosinolates increased significantly with elevation and were negatively correlated with herbivore damage in the field. In oviposition preference assays, P. brassicae females laid fewer eggs on plants from high-elevation populations, although larval performance was similar on populations from different elevations. Taken together, these results support the prediction that species distributed along elevation gradients exhibit genetic variation in chemical defenses, which can have consequences for interactions with herbivores in the field.

Thermal dependence of feeding performance and resting metabolic expenditure in different altitudinal populations of toad-headed lizards

Inter-population variations in growth rate can result from independent or interactive effects of genetic and environmental factors, and be induced by some physiological differences as well. Toad-headed lizards (Phrynocephalus vlangalii) from a higher-elevation population were shown to have a higher growth rate than those from a lower-elevation population. The physiological basis of growth rate variation in this species is not well understood. Here, we investigated the feeding performance and resting metabolic rate (RMR) of lower- and higher-elevation individuals at different test ambient temperatures to evaluate the role of differences in energy intake, assimilation efficiency and metabolic expenditure on growth rate variations. Within the range of 25−35 °C, lizard RMR increased with increasing test ambient temperature, but food intake, apparent digestive coefficient (ADC, food energy minus faecal energy divided by food energy), and assimilation efficiency (AE, food energy minus faecal and urinary energy divided by food energy) were less thermally sensitive in both populations. Higher-elevation lizards tended to eat more food and have a lower RMR than lower-elevation ones, despite the lack of differences in ADC and AE. Our result showed that more energy intake and reduced maintenance cost may be associated with the higher growth rate of higher-elevation lizards. Accordingly, inter-population differences in energy acquisition and expenditure could act as potential sources for geographic variation in growth rate.

Parallel evolution of gene classes, but not genes: Evidence from Hawai'ian honeycreeper populations exposed to avian malaria.

Adaptation in nature is ubiquitous, yet characterizing its genomic basis is difficult because population demographics cause correlations with nonadaptive loci. Introduction events provide opportunities to observe adaptation over known spatial and temporal scales, facilitating the identification of genes involved in adaptation. The pathogen causing avian malaria, Plasmodium relictum, was introduced to Hawai'i in the 1930s and elicited extinctions and precipitous population declines in native honeycreepers. After a sharp initial population decline, the Hawai'i 'amakihi (Chlorodrepanis virens) has evolved tolerance to the parasite at low elevations where P.relictum exists, and can sustain infection without major fitness consequences. High-elevation, unexposed populations of 'amakihi display little to no tolerance. To explore the genomic basis of adaptation to P.relictum in low-elevation 'amakihi, we genotyped 125 'amakihi from the island of Hawai'i via hybridization capture to 40,000 oligonucleotide baits containing SNPs and used the reference 'amakihi genome to identify genes potentially under selection from malaria. We tested for outlier loci between low- and high-elevation population pairs and identified loci with signatures of selection within low-elevation populations. In some cases, genes commonly involved in the immune response (e.g., major histocompatibility complex) were associated with malaria presence in the population. We also detected several novel candidate loci that may be implicated in surviving malaria infection (e.g., beta-defensin, glycoproteins and interleukin-related genes). Our results suggest that rapid adaptation to pathogens may occur through changes in different immune genes, but in the same classes of genes, across populations.

The genetic prehistory of the Andean highlands 7000 years BP though European contact.

The peopling of the Andean highlands above 2500 m in elevation was a complex process that included cultural, biological, and genetic adaptations. Here, we present a time series of ancient whole genomes from the Andes of Peru, dating back to 7000 calendar years before the present (BP), and compare them to 42 new genome-wide genetic variation datasets from both highland and lowland populations. We infer three significant features: a split between low- and high-elevation populations that occurred between 9200 and 8200 BP; a population collapse after European contact that is significantly more severe in South American lowlanders than in highland populations; and evidence for positive selection at genetic loci related to starch digestion and plausibly pathogen resistance after European contact. We do not find selective sweep signals related to known components of the human hypoxia response, which may suggest more complex modes of genetic adaptation to high altitude.

Climate change causes upslope shifts and mountaintop extirpations in a tropical bird community.

Montane species worldwide are shifting upslope in response to recent temperature increases. These upslope shifts are predicted to lead to mountaintop extinctions of species that live only near mountain summits, but empirical examples of populations that have disappeared are sparse. We show that recent warming constitutes an "escalator to extinction" for birds on a remote Peruvian mountain-high-elevation species have declined in both range size and abundance, and several previously common mountaintop residents have disappeared from the local community. Our findings support projections that warming will likely drive widespread extirpations and extinctions of high-elevation taxa in the tropical Andes. Such climate change-driven mountaintop extirpations may be more likely in the tropics, where temperature seems to exert a stronger control on species' range limits than in the temperate zone. In contrast, we show that lowland bird species at our study site are expanding in range size as they shift their upper limits upslope and may thus benefit from climate change.

Relationship between epidemiologic surveillance with geo-climatic variables during Zika outbreak in Guerrero State, Mexico 2016

Background: Zika like dengue and chikungunya represent public health problems. Cases of ZIKV infection are emerging in the Americas, from Argentina spread until Brazil and Colombia, later entry to Mexico and managed to establish itself in most of the states.Methods: The cases (2016-2017) of epidemiological surveillance of the first outbreak of Zika in Guerrero were used. The incidence rates (IR) for each municipality were estimated (cases/100 000 inhabitants) to develop the first maps at the municipal and state level; which aimed to explore the relationship between Zika cases and geo-climatic variables.Results: At January 3, 2017 in Guerrero State [epidemiological week (SE) 52 of the year 2016] were reported 861 confirmed ZIKV cases (10.06% of total registered cases at federal level). Guerrero State it was placed within the six states with the largest number of cases: Veracruz (1967), Yucatan (1284), Nuevo Leon (844), Chiapas (804) and Oaxaca (507); concentrated 73.26% (6 267/8 554) of the country's cases. In this study we identified the geo-environmental factors associated with ZIKV occurrence in each municipality of the Guerrero State: very high rain (1201-1460 mm), low elevation (2-398 masl) and high population density (≥62071 inhabitants/km2).Conclusions: This study represents the first approach to Zika outbreak in Guerrero State. Although tests of spatial nature are not presented; the maps presented show how the characteristics by region have high influence and that the most affected areas were the coastal areas: Acapulco, Small Coast and Big Coast.

Morphometric differentiation and geographic variation among populations of Boana cordobae (Anura: Hylidae): effect to age

We estimated differences in body size and age structure of six populations of Boana cordobae living at different altitudes, 808-2 310 m.a.s.l. in Córdoba and San Luis provinces (Argentina). We measured 15 morphometric variables and used skeletochronology to age determination of 79 individuals. Morphometric variables showed significant differences between sexes, being females larger than males, even when the effect of age was taken into account. We found a significant relationship between age and most of the morphometric variables. When removing the effects of age, we found significant inter-population differences in body size. Males from the high-elevation populations were larger than individuals from low-elevation populations. These results suggest that a difference in age structure between populations is a main factor for the geographic variation in body size of this species.