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Anurans vary in body coloration and frequently exhibit color polymorphism, with selection by predation pressure favoring more cryptic animals. Spatial differentiation may also favor color polymorphism in some species, since cryptic morphotypes can use substrates that better match their coloration. Boana pulchella is a polymorphic species with green and brown morphotypes, but its polymorphism remains poorly understood. The aim of the present study was to determine the functionality of color polymorphism in B. pulchella as a defense strategy. Artificial green and brown clay models were placed in environments with green and brown background to determine if the two morphotypes of B. pulchella experience different frequencies of attacks. We expected that more conspicuous morphs are attacked more frequently. The attack rate, which suggests predation intent, on the models was 9.57%. The marks observed in the artificial models were left by both mammals and birds. The number of damaged models did not significantly differ between the different background environments. The results indicate that B. pulchella morphotypes are equally cryptic to predators in the studied environments. In conclusion, probably color polymorphism in B. pulchella is not operating as a defensive strategy, and other selective forces may be acting in the maintenance of color polymorphism in this species.

The ability to predict amphibian breeding across landscapes is important for informing land management decisions and helping biologists better understand and remediate factors contributing to declines in amphibian populations. We built geospatial models of likely breeding habitats for each of four amphibian species that breed in Yellowstone National Park (YNP). We used field data collected in 2000-2002 from 497 sites among 16 basins and predictor variables from geospatial models produced from remotely sensed data (e.g., digital elevation model, complex topographic index, landform data, wetland probability, and vegetative cover). Except for 31 sites in one basin that were surveyed in both 2000 and 2002, all sites were surveyed once. We used polytomous regression to build statistical models for each species of amphibian from (1) field survey site data only, (2) field data combined with data from geospatial models, and (3) data from geospatial models only. Based on measures of receiver operating characteristic (ROC) scores, models of the second type best explained likely breeding habitat because they contained the most information (ROC values ranged from 0.70 to 0.88). However, models of the third type could be applied to the entire YNP landscape and produced maps that could be verified with reserve field data. Accuracy rates for models built for single years were highly variable, ranging from 0.30 to 0.78. Accuracy rates for models built with data combined from multiple years were higher and less variable, ranging from 0.60 to 0.80. Combining results from the geospatial multiyear models yielded maps of \"core\" breeding areas (areas with high probability values for all three years) surrounded by areas that scored high for only one or two years, providing an estimate of variability among years. Such information can highlight landscape options for amphibian conservation. For example, our models identify alternative areas that could be protected for each species, including 6828-10  764 ha for tiger salamanders, 971-3017 ha for western toads, 4732-16  696 ha for boreal chorus frogs, and 4940-19 690 ha for Columbia spotted frogs.

Aim Habitat loss and degradation are the factors threatening the largest number of amphibian species. However, quantitative measures of habitat availability only exist for a small subset of them. We evaluated the relationships between habitat availability, extinction risk and drivers of threat for the world's amphibians. We developed deductive habitat suitability models to estimate the extent of suitable habitat and the proportion of suitable habitat (PSH) inside the geographic range of each species, covering species and areas for which little or no high-resolution distribution data are available. Location Global. Methods We used information on habitat preferences to develop habitat suitability models at 300-m resolution, by integrating range maps with land cover and elevation. Model performance was assessed by comparing model output with point localities where species were recorded. We then used habitat availability as a surrogate of area of occupancy. Using the IUCN criteria, we identified species having narrow area of occupancy, for which extinction risk is likely underestimated. Results We developed models for 5363 amphibians. Validation success of models was high (94%), being better for forest specialists and generalists than for open habitat specialists. Generalists had proportionally more habitat than forest or open habitat specialists. The PSH was lower for species having small geographical ranges, currently listed as threatened, and for which habitat loss is recognized as a threat. Differences in habitat availability among biogeographical realms were strong. We identified 61 forest species for which the extinction risk may be higher that currently assessed in the Red List, due to limited extent of suitable habitat. Main conclusions Habitat models can accurately predict amphibian distribution at fine scale and allow describing biogeographical patterns of habitat availability. The strong relationship between amount of suitable habitat and extinction threat may help the conservation assessment in species for which limited information is currently available.

Physiological thermal-tolerance limits of terrestrial ectotherms often exceed local air temperatures, implying a high degree of thermal safety (an excess of warm or cold thermal tolerance). However, air temperatures can be very different from the equilibrium body temperature of an individual ectotherm. Here, we compile thermal-tolerance limits of ectotherms across a wide range of latitudes and elevations and compare these thermal limits both to air and to operative body temperatures (theoretically equilibrated body temperatures) of small ectothermic animals during the warmest and coldest times of the year. We show that extreme operative body temperatures in exposed habitats match or exceed the physiological thermal limits of most ectotherms. Therefore, contrary to previous findings using air temperatures, most ectotherms do not have a physiological thermal-safety margin. They must therefore rely on behavior to avoid overheating during the warmest times, especially in the lowland tropics. Likewise, species living at temperate latitudes and in alpine habitats must retreat to avoid lethal cold exposure. Behavioral plasticity of habitat use and the energetic consequences of thermal retreats are therefore critical aspects of species' vulnerability to climate warming and extreme events.

Integral projection models (IPMs) can estimate the population dynamics of species for which both discrete life stages and continuous variables influence demographic rates. Stochastic IPMs for imperiled species, in turn, can facilitate population viability analyses (PVAs) to guide conservation decision-making. Biphasic amphibians are globally distributed, often highly imperiled, and ecologically well suited to the IPM approach. Herein, we present a stochastic size- and stage-structured IPM for a biphasic amphibian, the U.S. federally threatened California tiger salamander (CTS) (Ambystoma californiense). This Bayesian model reveals that CTS population dynamics show greatest elasticity to changes in juvenile and metamorph growth and that populations are likely to experience rapid growth at low density. We integrated this IPM with climatic drivers of CTS demography to develop a PVA and examined CTS extinction risk under the primary threats of habitat loss and climate change. The PVA indicated that long-term viability is possible with surprisingly high (20%–50%) terrestrial mortality but simultaneously identified likely minimum terrestrial buffer requirements of 600–1000 m while accounting for numerous parameter uncertainties through the Bayesian framework. These analyses underscore the value of stochastic and Bayesian IPMs for understanding both climate-dependent taxa and those with cryptic life histories (e.g., biphasic amphibians) in service of ecological discovery and biodiversity conservation. In addition to providing guidance for CTS recovery, the contributed IPM and PVA supply a framework for applying these tools to investigations of ecologically similar species.

Anthropogenic habitat disturbances often create discontinuity between the multiple classes of natural habitats that many species need to complete their life cycles. This process, termed habitat split , is common across Neotropical landscapes and negatively impacts several classes of vertebrates and invertebrates. For instance, habitat split—often arising from habitat loss and fragmentation—exposes aquatic-breeding amphibians to risky migrations through disturbed environments as they move between natural terrestrial habitats and aquatic breeding sites, contributing to population declines. In contrast, terrestrial-breeding amphibians should not be impacted by this form of habitat split because they may spend their entire life cycle in the same terrestrial habitat. We used available field data and natural history information to develop Individual-Based Models (IBM) that account for seasonal migrations to quantify the impact of different levels of habitat split on population survival of Brazilian amphibians. Our IBM results align with our observed field data, indicating a disproportionate decline in the occurrence and population abundances of migrating aquatic-breeding amphibians compared to non-migratory terrestrial-breeding amphibians in regions with high habitat split. An intermediate dispersal optimum for aquatic-breeding frogs was suggested by our IBM, indicating that long-distance dispersal might not always be advantageous for population persistence, likely due to tradeoffs between reproduction and migration risk. Our spatial model framework factoring breeding migration could be applied widely across ecoregions of interest and help inform targeted habitat restoration strategies to curb localized amphibian declines and extinctions.

Pool-breeding amphibian populations operate at multiple scales, from the individual pool to surrounding upland habitat to clusters of pools. When metapopulation dynamics play a role in long-term viability, conservation efforts limited to the protection of individual pools or even pools with associated upland habitat may be ineffective over the long term if connectivity among pools is not maintained. Connectivity becomes especially important and difficult to assess in regions where suburban sprawl is rapidly increasing land development, road density, and traffic rates. We developed a model of connectivity among vernal pools for the four ambystomatid salamanders that occur in Massachusetts and applied it to the nearly 30,000 potential ephemeral wetlands across the state. The model was based on a modification of the kernel estimator (a density estimator commonly used in home range studies) that takes landscape resistance into account. The model was parameterized with empirical migration distances for spotted salamanders (Ambystoma maculatum), dispersal distances for marbled salamanders (A. opacum), and expert-derived estimates of landscape resistance. The model ranked vernal pools in Massachusetts by local, neighborhood, and regional connectivity and by an integrated measure of connectivity, both statewide and within ecoregions. The most functionally connected pool complexes occurred in southeastern and northeastern Massachusetts, areas with rapidly increasing suburban development. In a sensitivity analysis estimates of pool connectivity were relatively insensitive to uncertainty in parameter estimates, especially at the local and neighborhood scales. Our connectivity model could be used to prioritize conservation efforts for vernal-pool amphibian populations at broader scales than traditional pool-based approaches.

Context Habitat fragmentation and loss are major contributing factors in the global biodiversity crisis. This is especially concerning for low-dispersing organisms in anthropized areas, where artificial elements separating suitable habitat patches impede landscape connectivity, compromising long-term population viability. Robust comparative assessments of regional population connectivity can drive evidence-based conservation measures for biological communities, but require comprehensive field surveys to provide reliable inferences. Objectives We focused on amphibians, low-dispersing taxa with declining populations worldwide, primarily due to habitat loss and fragmentation. We assessed patterns of landscape connectivity in 16 native amphibian species grouped in four communities in the most populated region in Spain (Community of Madrid). Methods We surveyed 2303 water bodies across the entire region to characterize amphibian communities and developed whole-range distribution models relating species presence data and remote sensing covariates. Then, we projected predicted global distributions in the study region with high resolution and used landscape resistance models and clustering analyses to reconstruct connectivity networks of all species and identify potential ecological corridors and barriers contributing to population fragmentation. Results We recorded 18–866 breeding sites per species, and generated models with high statistical performance. Connectivity varied spatially and across communities and species, highlighting barriers to dispersal comprising natural (mountains, rivers) and artificial features (water reservoirs, dammed rivers, urban areas), and also ecological corridors, including peri-urban green areas, river valleys, moorlands and mountain passes. Conclusions Our work presents a novel methodological framework leveraging data from local (field surveys) and global (online databases) scales across multiple species, enabling robust assessment of community-level connectivity patterns to inform conservation planning.

Background Amphibians are the most globally threatened vertebrates, facing a particularly high risk of extinction in some regions, such as the Mediterranean basin. Within this region, the genus Salamandrina , comprising two species of notable conservation concerns, managed to persist throughout historical climate changes exclusively along the Italian peninsula. Among the main threats to this genus are habitat loss and climate change, as this salamander is adapted to humid forests and relies heavily on water sources, such as small streams, for reproduction. In this study, we employed fine-scale species distribution models (SDMs) to estimate areas projected to remain suitable for Salamandrina species in the future and areas expected to become unsuitable, incorporating bioclimatic, topographic, and habitat variables. We also evaluated landscape connectivity and identified ecological corridors that could facilitate movement through circuit-theory techniques, analyzing potential changes under different scenarios. Additionally, considering known hybridization events in a contact zone between the two species, we measured connectivity to assess whether this process might change in the future. Results We found several suitable areas that mostly align with the known ranges of both species. Future projections showed an overall decline in habitat suitability, with a northwestern shift. While strong in certain areas, landscape connectivity is expected to decrease overall. Specifically, our results revealed several corridors for S. perspicillata (the northern species), with higher connectivity values in the Central Apennines. For S. terdigitata (the southern species), a crucial corridor in the Catena Costiera Massifs, in the western southernmost region of the Italian peninsula, connects two key conservation areas. In the contact zone, we identified corridors that could favor hybridization between the species, with predictions suggesting an increase. Conclusions Our findings inform the long-term conservation of a unique salamander genus. Strengthening conservation measures on Salamandrina species in areas predicted to become unsuitable or in areas that could become suitable and serve as ecological corridors will be critical. Furthermore, future monitoring efforts should focus on the corridors identified in the contact zone to assess whether the hybridization process is ongoing and at what rate.

Comparative phylogeographic studies often support shared divergence times for co-distributed species with similar life histories and habitat specializations. During the late Holocene, West Africa experienced aridification and the turnover of rain forest habitats into savannas. These fragmented rain forests harbor impressive numbers of endemic and threatened species. In this setting, populations of co-distributed rain forest species are expected to have diverged simultaneously, whereas divergence events for species adapted to savanna and forest-edge habitats should be absent or idiosyncratic. We conducted a Bayesian analysis of shared evolutionary events to test models of population divergence for 20 species of anurans (frogs) and squamates (lizards and snakes) that are distributed across the Dahomey Gap, a climate change-induced savanna barrier responsible for fragmenting previously contiguous rain forests of Ghana into two regions: the Togo-Volta Hills and the Southwestern Forests. A model of asynchronous diversification is supported for anurans and squamates, suggesting that drivers of diversification are not specifically related to ecological and life history associations with habitat types. Instead, the wide variability of genetic divergence histories exhibited by these species suggests that biodiversity in this region has been shaped by diversification events that extend beyond the Holocene. Comparisons of the genealogical divergence index, a measure of the genetic divergence between populations due to the combined effects of genetic isolation and gene flow, illustrate that these populations represent a broad sampling of the speciation continuum.