Explore the vast range of titles available.

Allometric constraint is a product of natural selection and physical laws, particularly with respect to body size and traits constrained by properties thereof, such as metabolism, longevity, and vocal frequency. Allometric relationships are often conserved across lineages, indicating that physical constraints dictate scaling patterns in deep time, despite substantial genetic and ecological divergence among organisms. In particular, acoustic allometry (sound frequency ~ body size) is conserved across frogs, in defiance of massive variation in both body size and frequency. Here, we ask how many instances of allometric escape have occurred across the frog tree of life using a Bayesian framework that estimates the location, number, and magnitude of shifts in the adaptive landscape of acoustic allometry. Moreover, we test whether ecology in terms of calling site could affect these relationships. We find that calling site has a major influence on acoustic allometry. Despite this, we identify only four major instances of allometric escape, potentially deriving from ecomorphological adaptations to new signal modalities. In these instances of allometric escape, the optima and strength of the scaling relationship are different than expected for most other frog species, representing new adaptive regimes of body size ~ call frequency. Allometric constraints on frog calls are highly conserved and have rarely allowed escape, despite frequent invasions of new adaptive regimes and dramatic ecomorphological divergence. Our results highlight the rare instances in which natural and sexual selection combined can overcome physical constraints on sound production. Allometric constraints in frogs are highly conserved and have rarely promoted allometric escape despite frequent invasions of new adaptive regimes of sound frequency and dramatic ecomorphological divergence in body size and calling site. In this study, we highlight instances in which natural and sexual selection combined could overcome physical constraints on sound production.

Aim Future climate changes may affect species distribution and their genetic diversity, hampering species adaptation to a new climate or tracking the suitable conditions. Amphibians have high sensitivity to environmental degradation and changes in temperature and humidity. Thus, the expected climatic changes by the end‐of‐century (EOC 2100) may cause local or complete extinction of some species. Here, we address the effects of climate change on genetic and phylogeographical diversity, together with the geographical distribution of the South American treefrog Scinax squalirostris Lutz, 1925. Furthermore, we assess how protected areas will conserve its genetic variation. Location South America. Methods We combined Ecological Niche Modelling and genetic simulations to predict the effects of climate change on the geographical distribution, genetic diversity, structure and phylogeographical diversity of Scinax squalirostris, using two scenarios of CO2 emission. We also performed a spatial analysis to investigate the effectiveness of the current Protected Areas (PAs) to preserve the species’ genetic and phylogeographical diversity. Results Scinax squalirostris' geographical range will potentially increase in the future due to the expansion of suitable areas towards its southern distribution, despite the shrinking of suitable areas in the northern part of its current distribution. Besides the shifts in suitable areas, our findings point to a genetic homogenization across the geographical range of S. squalirostris due to the displacement and loss of genetic ancestry clusters. Although existing PAs are conserving the current genetic diversity, they conserve less phylogeographical diversity than expected by chance. Scinax squalirostris may shift its distribution into areas with lower number of PAs, compromising its future conservation. Main conclusions Climate change will potentially increase S. squalirostris range size, however, not towards regions where most of the current established PAs are located, hence driving to homogenization and loss of genetic diversity, and leading to a gap of conservation within PAs.

Amphibians inhabiting agricultural areas are constantly exposed to large amounts of chemicals, which reach the aquatic environment during the rainy season through runoff, drainage, and leaching. We performed a comet assay on the erythrocytes of tadpoles found in the surroundings of agricultural fields (soybean and corn crops), where there is an intense release of several kinds of pesticides in different quantities. We aimed to detect differences in the genotoxic parameters between populations collected from soybeans and cornfields, and between them and tadpoles sampled from non-agricultural areas (control group). Tadpoles collected from ponds located at soybean fields had significantly more DNA damage, followed by tadpoles collected from cornfields. In contrast, animals sampled from non-agricultural areas had the lowest incidence of DNA damage. In addition, we found a negative correlation between the parameters of the comet assay and the area of the ponds surrounding soybean. This correlation indicates a possible dilution effect in the concentration of pesticides. Finally, Physalaemus cuvieri Fitzinger, 1826 seems to be a good bioindicator for detecting the genotoxic effects of field agricultural insecticides; therefore, we suggest that this species should be used in environmental biomonitoring studies, since it is common and abundant where it occurs.

ContextDeclining in biodiversity in the Anthropocene is mostly a result of habitat loss due to changes in the landscape.ObjectivesHere, we address how landscape composition and configuration affect anuran diversity in agricultural landscapes in the Brazilian Cerrado ecoregion.MethodsWe sampled 29 breeding sites during the rainy season using auditory census and visual encounters to record anuran species richness, and specialist, generalist and dominant species richness. For each sampling site, we estimated eight landscape metrics at five spatial scales.ResultsWe recorded 36 species from seven anuran families, 17 habitat specialist and 19 habitat generalists. We found that aquatic habitat cover (%) and number of aquatic patches played a positive effect on both total anuran richness and richness of dominant species. However, landscape compositional heterogeneity and aquatic habitat isolation negatively influenced community rarity, and abundance of habitat specialist species. In addition, more diverse anuran communities were found in areas where the amount and number of aquatic habitat patches were greater.ConclusionsOur results emphasize the importance of maintaining high amounts of waterbodies and high aquatic habitat connectivity across the landscapes. Moreover, rare species and habitat specialist species are sensitive to landscape composition and configuration, respectively. Therefore, water body amount and connectivity must be considered in conservation plans to mitigate anuran community loss in agricultural landscapes.

Geographical gradients of body size express climate-driven constraints on animals, but whether they exist and what causes them in ectotherms remains contentious. For amphibians, the water conservation hypothesis posits that larger bodies reduce evaporative water loss (EWL) along dehydrating gradients. To address this hypothesis mechanistically, we build on well-established biophysical equations of water exchange in anurans to propose a state-transition model that predicts an increase of either body size or resistance to EWL as alternative specialization along dehydrating gradients. The model predicts that species whose water economy is more sensitive to variation in body size than to variation in resistance to EWL should increase in size in response to increasing potential evapotranspiration (PET). To evaluate the model predictions, we combine physiological measurements of resistance to EWL with geographic data of body size for four different anuran species. Only one species, Dendropsophus minutus, was predicted to exhibit a positive body size–PET relationship. Results were as predicted for all cases, with one species—Boana faber—showing a negative relationship. Based on an empirically verified mathematical model, we show that clines of body size among anurans depend on the current values of those traits and emerge as an advantage for water conservation. Our model offers a mechanistic and compelling explanation for the cause and variation of gradients of body size in anurans.

Despite the widespread use of ecological niche models (ENMs) for predicting the responses of species to climate change, these models do not explicitly incorporate any population‐level mechanism. On the other hand, mechanistic models adding population processes (e.g. biotic interactions, dispersal and adaptive potential to abiotic conditions) are much more complex and difficult to parameterize, especially if the goal is to predict range shifts for many species simultaneously. In particular, the adaptive potential (based on genetic adaptations, phenotypic plasticity and behavioral adjustments for physiological responses) of local populations has been a less studied mechanism affecting species’ responses to climatic change so far. Here, we discuss and apply an alternative macroecological framework to evaluate the potential role of evolutionary rescue under climate change based on ENMs. We begin by reviewing eco‐evolutionary models that evaluate the maximum sustainable evolutionary rate under a scenario of environmental change, showing how they can be used to understand the impact of temperature change on a Neotropical anuran species, the Schneider's toad Rhinella diptycha. Then we show how to evaluate spatial patterns of species’ geographic range shift using such models, by estimating evolutionary rates at the trailing edge of species distribution estimated by ENMs and by recalculating the relative amount of total range loss under climate change. We show how different models can reduce the expected range loss predicted for the studied species by potential ecophysiological adaptations in some regions of the trailing edge predicted by ENMs. For general applications, we believe that parameters for large numbers of species and populations can be obtained from macroecological generalizations (e.g. allometric equations and ecogeographical rules), so our framework coupling ENMs with eco‐evolutionary models can be applied to achieve a more accurate picture of potential impacts from climate change and other threats to biodiversity.

The level of species richness of amphibians found in Brazil is the greatest in the world. Despite increasing anthropic pressures on the Brazilian Cerrado and Amazon biomes, several new anuran species are described each year. In this study, two new species of Rhinella found in Brazil are described and assigned to the Rhinella margaritifera species group, based on morphological features. Rhinella sebbeni sp. nov. occurs in forested environments in the Cerrado biome and is characterized by the combination of the following features: snout–vent length (SVL; range  =  48.5–59.7 mm in males, and 54.7–66.7 mm in females); presence of bony protrusion at the angle of jaws and rostral keel at the tip of snout; skin on the dorsum with a few granules, but more concentrated on the flanks; parotoid gland is well delineated and small and elliptical in shape showing a lateral line of tubercles. Rhinella gildae sp. nov. is found in southern Amazonia and is characterized by the combination of following features: SVL (range  =  69.6–76.4 mm in males); cephalic crests poorly developed; parotoid gland without lateral line of tubercles; in dorsal view, supratympanic crest not exceeding the angle of the jaws; and presence of a vertebral line. We discuss data on morphological variation, natural history attributes, and distribution of the two new species.

Adenomera andreae and A. hylaedactyla are two widespread Amazonian frogs that have been traditionally distinguished from each other by the use of different habitats, toe tip development, and more recently through advertisement calls. Yet, taxonomic identification of these species has always been challenging. Herein we undertake a review of type specimens and include new phenotypic (morphology and vocalization) and mitochondrial DNA information for an updated diagnosis of both species. Our morphological analysis indicates that the single type (holotype) of A. hylaedactyla could either belong to lineages associated with Amazonian forest-dwelling species (A. andreae clade) or to the open-formation morphotype (A. hylaedactyla clade). Given the holotype's poor preservation, leading to the ambiguous assignment of character states for toe tip development, as well as a vague type locality encompassing a vast area in eastern Ecuador and northern Peru, the identity of this specimen is uncertain. Morphology of toe tip fragments and the original species description suggest that A. hylaedactyla could correspond to at least two described species (A. andreae or A. simonstuarti) or additional unnamed genetic lineages of the A. andreae clade, all bearing toe tips expanded into discs. Analysis of morphometric data, however, clustered the holotype with the Amazonian open-formation morphotype (toe tips unexpanded). While additional data can be obtained from the holotype of A. hylaedactyla, at this time this type cannot be unequivocally assigned to any species of Adenomera distributed across eastern Ecuador and Peru's northernmost region of Loreto. For the time being, the name A. hylaedactyla still accommodates the only Amazonian open-habitat species. As to the type series of Adenomera andreae, a forest-associated species with toe tips fully expanded (developed into small discs) from eastern Brazilian Amazonia, we found that one of its paratypes shares a morphotype with the open-habitat species and is reassigned to A. hylaedactyla. With the taxonomic identity of A. hylaedactyla unresolved, formal descriptions of cryptic species complexes within the A. andreae clade distributed across the type locality of A. hylaedactyla run the risk of a possible future synonymization with A. hylaedactyla. Yet, not naming more circumscribed and potentially threatened cryptic species puts them at risk, as they would probably not qualify for conservation funding. Given the current fire crisis in the Amazon Basin, the risk of losing species before they are described far outweighs the risk of synonymization. We recommend that researchers prioritize descriptions based on the potential extinction risk of new species.

A new species of Chaunus, apparently related to Chaunusarenarum, Chaunus rubescens, and Chaunus achavali is described. The new species occupies Cerrado habitats in southwestern Piauí and Bahia states and in northwestern Minas Gerais state, Brazil. The species is characterized by anterior interruption of the supraocular crest; weakly developed cranial crests; short and robust limbs; several pointed spiculae on dorsum, head, and limbs; male coloration; small to medium size; and by the short and narrow head.

A calcified pseudodontoid in the mandibular symphysis of Leptodactylus troglodytes was described from fresh, macerated, and cleared/double-stained preparations. Histology confirmed that the pseudodontoid was mineralized and composed of fibrocartilage. This structure was found in all specimens of both sexes, suggesting a role in either prey capture or defense rather than in courtship or combat. The structure in L. troglodytes differed morphologically and histologically from the pseudodontoid observed in other Leptodactylus and in other neobatrachian species. Our sampling indicates that the presence and morphology of the pseudodontoid is synapomorphic to a clade recently named Tinctanura. However, a broader sample is still necessary to strengthen this assessment.