Terrestrial amphibians may dehydrate when exposed to low humidity, representing an important factor affecting spatial distribution and community composition. In this study we investigated whether rates of dehydration and rehydration are able to explain the spatial distribution of an anuran community in a Restinga environment at the northern coast of the State of Bahia, Brazil, represented by 11 species distributed in 27 sample units. The environmental data set containing 20 variables was reduced to a few synthetic axes by principal component analysis (PCA). Physiological variables measured were rates of dehydration, rehydration from water, and rehydration from a neutral substrate. Multiple regression analyses were used to test the null hypothesis of no association between the environmental data set (synthetic axes of PCA) and each axis representative of a physiological variable, which was rejected (P < 0.001). Of 15 possible partial regressions only rehydration rate from neutral substrate vs. PC1 and PC2, rehydration rate from water vs. PC1, and dehydration rate vs. PC2 were significant. Our analysis was influenced by a gradient between two different groups of sample units: a beach area with high density of bromeliads and an environment without bodies of water with low density of bromeliads. Species of very specific natural history and morphological characters occur in these environments: Phyllodytes melanomystax and Scinax auratus, species frequently occurring in terrestrial bromeliads, and Ischnocnema paulodutrai, common along the northern coast of Bahia and usually found in forest remnants within environments with low number of bodies of water. In dry environments species with lower rates of dehydration were dominant, whereas species showing greater rates of dehydration were found predominantly in microhabitats with greater moisture or abundance of bodies of water.

Understanding the relationship between climate-driven habitat conditions and survival is key to preserving biodiversity in the face of rapid climate change. Hydroperiod—the length of time water is in a wetland—is a critical limiting habitat variable for amphibians as larvae must metamorphose before ponds dry. Changes in precipitation and temperature patterns are affecting hydroperiod globally, but the impact of these changes on amphibian persistence is poorly understood. We studied the responses of Boreal Chorus Frog (Pseudacris maculata) tadpoles to simulated hydroperiods (i.e., water level reductions) in the laboratory using individuals collected from ponds spanning a range of natural hydroperiods (Colorado Front Range, USA). To assess the effects of experimental hydroperiod reduction, we measured mortality, time to metamorphosis, and size at metamorphosis. We found that tadpoles grew at rates reflecting the hydroperiods of their native ponds, regardless of experimental treatment. Tadpoles from permanent ponds metamorphosed faster than those from ephemeral ponds across all experimental treatments, a pattern which may represent a predation selection gradient or countergradient variation in developmental rates. Size at metamorphosis did not vary across experimental treatments. Mortality was low overall but varied with pond of origin. Our results suggest that adaptation to local hydroperiod and/or predation and temperature conditions is important in P. maculata. Moreover, the lack of a plastic response to reduced hydroperiods suggests that P. maculata may not be able to metamorphose quickly enough to escape drying ponds. These results have important implications for amphibian persistence in ponds predicted to dry more quickly due to rapid climate change.

Where fecundity, mortality, immigration, or emigration differ among species, genotypes, environments, sexes, or age and size classes, we must expect differences in the composition and dynamics of populations and communities. However, as shown in this study on all-hybrid populations of the hemiclonal waterfrog Pelophylax esculentus, the reverse conclusion is not necessarily true: Population differences in genotype composition were not paralleled by differences in genotype-specific age and size distributions. We investigated 12 ponds with different ratios of diploid (LR) and triploid (LLR and LRR) hybrids and tested whether the pond-to-pond ratio differences result from differential survival of the three genotypes under different ecological conditions (selection hypothesis). This should then be reflected in the age and size distribution of the frogs. Age (determined through skeletochronology) and size (measured as snout–vent length) were related to eight ecological variables that in previous studies had been found to affect genotype ratios: temperature, dissolved oxygen, pH, pond size, amounts of submerged and floating pond vegetation, and proportions of forest and wetland area within 20 m of the pond. Only two of these eight variables had a significant effect on growth and survival: frogs in larger ponds were, on average, older and larger than frogs in smaller ponds, and body size also increased with water temperature. Since these relationships did not differ between genotypes and sexes, we conclude that ecological conditions are unlikely to exert their influence on population structure via differential individual performance. The conclusion is supported by our finding that across the 12 study ponds there was no significant relationship between the proportion of a particular genotype × sex category and the average age and size of the individuals belonging to that category. An alternative to the selection hypothesis is offered by the recently proposed gamete pattern hypothesis. It states that pond-to-pond differences in genotype ratios arise from different gamete production patterns of LLR, LR, and LRR males and females. But, so far, support for this hypothesis is also weak.

Supernumerary or B chromosomes are one of the main causes for numerical chromosomal variation in higher eukaryotes. These extragenetic elements have been studied for more than a century, with the goal of trying to understand their origin, and how they survive as a polymorphism in natural populations. Hypsiboas albopunctatus is a nocturnal hylid frog distributed in the central–eastern part of South America. Previously, variation in chromosome numbers was described for a population from Rio Claro, São Paulo, Brazil, in which a single small-sized, metacentric B chromosome was present in ca. 40% of the analyzed individuals (n = 17). We herein describe the presence of B chromosomes in populations of H. albopunctatus from northeastern Argentina (Corrientes and Misiones provinces), with unusual morphological and structural characteristics. The frequency of B chromosomes varied significantly among analyzed populations. We found four diploid numbers (2N = 22, 22 1B, 22 2B, and 22 3B), and in a few individuals mitotic instability occurred. C banding revealed variations in the heterochromatin (DAPI ) pattern between Bs with similar morphology, indicating the existence of two new structural variants of these supernumerary elements in H. albopunctatus (B1 and B2). Nucleolar organizer regions marked positively on the eighth pair, coincident with the location of ribosomal DNA as demonstrated with fluorescent in situ hybridization, but Bs did not mark positive with these two techniques. Also, fluorescent in situ hybridization with telomeric probes showed no differences in location and intensity between Bs and autosomal chromosomes. The present communication is the first case of B chromosome polymorphisms in hylid frogs and the sixth reported in Anura.

The Red-headed Amazon River Turtle (Podocnemis erythrocephala) is the smallest species of the family Podocnemididae yet is frequently captured for human consumption. Our objectives were to (1) determine the relative abundance of this population and those factors that influence numbers, and (2) characterize the population structure using carapace length, sex ratio, and proportion of adults to verify the influence of sample methods and environmental factors. We sampled turtles in 2003–2008 in the Ayuanã River, the middle Rio Negro, Amazonas State, Brazil. We captured turtles using trammel nets and freediving. Females were larger and weighed more than males. The capture method influenced the size, sex ratio, percentage of juveniles, and the capture index. This population of P. erythrocephala had a sex ratio of 0.41male:1female and 40% were juveniles. The frequency of recaptures was ≤ 22% of a sample (n = 4432), indicating that only a part of the population was captured. The low density of humans (one person per 3.4 km²) living in the region, and having the nesting beaches distributed along the river, probably contributes to the large number of turtles captured. However, these natural populations of P. erythrocephala need to have long-term monitoring in this region in order to monitor the effect of human's consuming this species; this effect can only be quantified by long-term monitoring.

Podocnemis erythrocephala é a menor espécie do gênero e uma das três espécies mais capturadas para o consumo humano na bacia do Rio Negro. Os objetivos deste estudo foram (1) estudar a abundância relativa da população e os fatores que a influenciam; (2) caracterizar a estrutura populacional quanto ao comprimento da carapaça, razão sexual e a proporção de indivíduos imaturos na área de estudo e verificar a influência dos métodos de amostragem e dos fatores ambientais sobre estes parâmetros. As amostragens ocorreram desde novembro de 2003–2008 no rio Ayuanã, no médio Rio Negro, estado do Amazonas, Brasil. Para as capturas foram utilizadas as técnicas de mergulho livre e trammel nets. O dimorfismo sexual de tamanho foi confirmado, as fêmeas foram maiores e mais pesadas do que os machos. O método de amostragem influiu sobre o tamanho, razão sexual, percentual de juvenis e no índice de captura por esforço. A população de P. erythrocephala é caracterizada por uma razão sexual de 0,41♂:1♀ e por ter 40% (indivíduos) imaturos. As taxas de recapturas foram inferiores a 22% durante o estudo apesar de terem sido marcados 4432 indivíduos indicando que apenas uma pequena parcela da população foi capturada. A baixa densidade humana na região (um habitante para cada 3,4 km²) associada a locais de reprodução distribuídos ao longo de todo o rio provavelmente contribuam para o grande número de indivíduos encontrados. No entanto as populações naturais de P. erythrocephala precisam ser monitoradas a longo prazo na região, pois o consumo desta espécie é uma realidade e os seu efeito na população só pode ser observado a longo prazo.

Optimal-escape theory predicts that flight initiation distance (predator–prey distance when fleeing starts) increases as predation risk increases; optimal-refuge-use theory predicts that time spent hiding in refuge increases as risk upon emergence increases. I tested predictions of an extension of escape theory to a scenario in which an immobile predator stands near an immobile prey. When a previously immobile predator moves, the probability of fleeing is predicted to increase as predation risk increases. This scenario corresponds to ambush. I also examined potential effects of three poorly understood risk factors on time spent hiding in refuge. In the lizard Sceloporus virgatus, probability of fleeing was greater when the predator turned toward rather than away from prey, stood closer to prey before moving, or was oriented parallel to the prey rather than facing in the opposite direction. These findings and previous work indicate that cost–benefit considerations govern responses to ambush predators as well as to openly approaching predators, extending escape theory to encounters in which both predator and prey are initially immobile. Hiding time was unaffected by starting distance (predator–prey distance when approach begins), was longer after the second of two successive approaches, and was shorter early in the day when thermal cost of refuge use was high than later when refuge temperatures were warmer. The positive correlation between first and second hiding times adds to evidence for a boldness syndrome in S. virgatus.

Dispersal is a key factor in shaping the genetic structure and population dynamics of species; thus, its understanding is a fundamental requirement in formulating appropriate conservation strategies. Higher rates of dispersal in one sex than the other are widespread in vertebrate species and often attributed to the genetic advantages of reduced inbreeding. This is well documented in birds and mammals but has rarely been reported in other vertebrate taxa. Here, we use 12 microsatellite loci to detect signatures of sex-biased dispersal in the Hot Spring Snake, Thermophis baileyi. This colubrid species is endemic to the Tibetan Plateau and strongly linked to habitats with hot springs. It is one of the world's highest altitude snake species, reaching up to 5000 m above sea level, and it is considered as endangered because of its limited range and the reduction of its natural habitat. Former studies have revealed a restricted gene flow and a high degree of population structure in this species. Here, we find a significantly higher variance of the assignment index and a significant heterozygote deficit in males. Accordingly, first-generation dispersers are identified only in males using frequency-based assignments with prior population information. Spatial autocorrelation analysis suggests a higher level of relatedness among females at smaller geographic scales compared with males. Mate-searching activities and female natal homing are suggested as major traits explaining greater female philopatry in T. baileyi. Our findings are important in the scope of conservation and management planning for the Hot Spring Snake in the future.

The High-Andean Frog (Dendropsophus labialis) is distributed along the Eastern Andes of Colombia between 1900 and 3600 m. We analyzed multiple traits to determine if acoustics and morphology covary with genealogical history or if they evolved following independent trajectories. We generated a phylogeny of D. labialis populations with the use of mitochondrial ribosomal gene (12S, val-RNA, 16S) and nuclear gene (proopiomelanocortin A [POMC]) sequences. Two well-supported clades that correspond to geographic distribution were recovered. Acoustic variation diverges according to genealogical history, but external morphology does not follow this pattern. The strong and congruent divergence observed in acoustic and genetic characters indicates that these two clades correspond to morphologically cryptic, parapatric species. We describe the Northern Clade as a new species (Dendropsophus luddeckei; the Southern Clade retains the name D. labialis). The low level of molecular divergence between two outgroup species, Dendropsophus pelidna and Dendropsophus meridensis, suggests D. pelidna is a junior subjective synonym of D. meridensis.

I describe a new species of hylid frog of the genus Nyctimystes from Fergusson Island off the southeastern peninsula of New Guinea. The new species is distinctive in being of moderate size, lacking a tubercle or lappet on the heel, and in having a vocal sac and slits, palpebral venation of vertically oriented lines with few cross-connections, basal webbing between the fingers, orange-yellow flash markings in the groin and hidden surfaces of the thighs, and a venter heavily flecked with brown. The new species is currently known only from the type locality, but it may range more widely across the D'Entrecasteaux Islands. It is morphologically most similar to N. persimilis from the mountains of the adjacent mainland of New Guinea.

There are currently eight described species in the lizard genus Xenosaurus. However, given their restricted habitat use (primarily limited to crevices or holes in rocks) and the limited ability to disperse among isolated populations, it is likely that more species of Xenosaurus await discovery and description. Herein we describe a new species of Xenosaurus from the Sierra Madre Oriental in the State of Hidalgo, Mexico. This new species differs from previously described species in lacking a neck band and in having two pale lines that angle up from the jaws and extend parasagittally along the neck.

Actualmente hay ocho especies de lagartijas descritas en el género Xenosaurus. Sin embargo, dado el uso restringido del hábitat (limitado principalmente a grietas y oquedades de rocas) y limitada habilidad de dispersión entre poblaciones aisladas, es probable que más especies de Xenosaurus sean descubiertas y descritas. Describimos una nueva especie de Xenosaurus de la Sierra Madre Oriental en el estado de Hidalgo, México. Esta nueva especie difiere de las especies previamente descritas por la ausencia de un collar nucal y por tener dos rayas claras que corren paralelamente a lo largo del cuello.