Amphibians are a clade of over 8,400 species that provide unique research opportunities and challenges. With amphibians undergoing severe global declines, we posit that assessing our current understanding of amphibians is imperative. Focusing on the past five years (2016–2020), we examine trends in amphibian research, data, and systematics. New species of amphibians continue to be described at a pace of ∼150 per year. Phylogenomic studies are increasing, fueling a growing consensus in the amphibian tree of life. Over 3,000 species of amphibians are now represented by expert-curated accounts or data in AmphibiaWeb, AmphibiaChina, BIOWEB, or the Amphibian Disease Portal. Nevertheless, many species lack basic natural history data (e.g., diet records, morphological measurements, call recordings) and major gaps exist for entire amphibian clades. Genomic resources appear on the cusp of a rapid expansion, but large, repetitive amphibian genomes still pose significant challenges. Conservation continues to be a major focus for amphibian research, and threats cataloged on AmphibiaWeb for 1,261 species highlight the need to address land use change and disease using adaptive management strategies. To further promote amphibian research and conservation, we underscore the importance of database integration and suggest that other understudied or imperiled clades would benefit from similar assessments of existing data.

The resolution of phylogenetic relationships within rapid radiations poses a significant challenge in systematic biology. However, the integration of genome-scale DNA data with multispecies coalescent-based tree inference methods offers a strategy to resolve historically recalcitrant nodes within radiations of closely related species. Here, we analyze a dataset of over 60,000 loci captured via double digest restriction site-associated DNA sequencing (ddRADseq) using both concatenation- and coalescent-based approaches to infer the phylogenetic relationships of the Antarctic notothenioid lineage Artedidraconinae. Previous studies identify artedidraconines as the most rapidly diversifying subclade of notothenioids, but evolutionary studies of the clade are stymied by pervasive phylogenetic and taxonomic uncertainty. The results of our phylogenomic analyses provide clarity to several long-standing challenges in the systematics of artedidraconines, including the deep paraphyly of Artedidraco. Our findings enable the construction of a classification that reflects phylogenetic relationships, including the description of a new genus and the resurrection of a classification of Notothenioidei that places Artedidraconinae as a subfamily of Harpagiferidae. This work provides a phylogenetic perspective for investigations of the tempo and mode of diversification in artedidraconines, which is likely to provide new insights on the dynamics of the notothenioid adaptive radiation as a whole.

We describe the first documented associations between an emmelichthyid and a pelagic tunicate. An in situ observation of larval and juvenile Japanese Rubyfish, Erythrocles schlegelii (Emmelichthyidae) was made during blackwater scuba dives in the epipelagic waters off the coast of the Philippines. The fish were in close association with the pelagic salp Pegea confoederata (Thaliacea; Salpidae), either drifting alongside a colony of salps or residing inside individual salp cavities. Our results describe and illustrate this behavior, highlighting a previously undocumented family of fishes that associates with pelagic gelatinous invertebrates. This finding also demonstrates the importance of community science to further our understanding of the early life history of marine fishes.

Odontesthes crossognathos, new species, is described from the Pelotas River basin, upper Uruguay River, southern Brazil. The new species is easily diagnosed by the possession of hypertrophied lips bearing numerous dermal papillae, a character absent in other species of the genus. The new species is also distinguished from congeners, except O. humensis, by having the upper jaw distinctly longer than the lower jaw and a subterminal mouth. These mouth morphology adaptations are probably related to the foraging behavior of the new species, which inhabits rivers with rapids and rocky bottoms in a high-altitude basin.

Odontesthes crossognathos, espécie nova, é descrita da bacia do rio Pelotas, alto rio Uruguai, sul do Brasil. A nova espécie é facilmente diagnosticável por possuir lábios hipertrofiados com numerosas papilas dérmicas, caráter ausente em outras espécies do gênero. A nova espécie também se distingue das congêneres, exceto de O. humensis, por ter a mandíbula superior distintamente mais longa do que a inferior e a boca subterminal. Essas adaptações na morfologia da boca provavelmente estão relacionadas ao comportamento de forrageamento da nova espécie, que habita rios de corredeiras e fundos rochosos em uma bacia de altitude elevada.

We assessed whether morphological variability in populations of Pituophis deppei is related to the ecogeographic conditions of the biogeographic provinces they inhabit. This study includes four biogeographic provinces where the Mexican Pine Snake is reported: the Mexican Plateau, the Trans-Mexican Volcanic Belt, the Sierra Madre Occidental, and the Sierra Madre Oriental, Mexico. Specimens from the four biogeographic provinces were selected to analyze ecogeographic and morphological variation in the Mexican Pine Snake. A total of 789 occurrence records and 20 climatic and environmental variables were used to evaluate the overlap, conservatism, and divergence of ecological niches among the four provinces using an ecological niche model (ENM) for each one. Morphological variability was analyzed using geometric morphometrics with linear and discrete data from 262 specimens. The ENM results indicate that the distribution area of P. deppei is subdivided into four well-defined regions of habitat suitability associated with the Mexican Plateau, the Trans-Mexican Volcanic Belt, the Sierra Madre Oriental, and the Sierra Madre Occidental, with contact zones at their borders. These results indicate low overlap among the four provinces. Niche conservatism and niche divergence were supported by three and two pairwise comparisons, respectively. At the morphological level, linear morphometrics, scutellation, and black spot pattern accounted for enough variability to discriminate the specimens found in the Trans-Mexican Volcanic Belt from those of the other three provinces. As expected, the pattern of variation in head shape consists of well-defined character states exclusive to each of the four provinces inhabited by P. deppei. All the comparisons from the multivariate analyses of variance of landmark configurations with CVA were statistically significant, and the rates of correct posterior classifications were all above 35.5%. The ecogeographic variables used show reduced explanatory and predictive power for the variation in the morphological characters analyzed. The morphological variation in P. deppei could result from factors not considered in the present study, such as differences in trophic ecology, limited gene flow, non-adaptative variation, or phylogeographic implications. In the latter case, the morphological results obtained are consistent with one southern lineage previously reported using the haplotype configuration of species of P. deppei. Finally, our geometric morphometric approach allowed us to analyze head shape variability in P. deppei.

Se evaluó si la variabilidad morfológica de las poblaciones de Pituophis deppei está relacionada con las condiciones ecogeográficas de las provincias biogeográficas que habita. Este estudio incluye cuatro provincias biogeográficas donde se reporta a la serpiente de pino mexicana: El Altiplano Mexicano, la Faja Volcánica Trans-Mexicana, la Sierra Madre Occidental y la Sierra Madre Oriental, México. Se seleccionaron especímenes de las cuatro provincias biogeográficas para el análisis de la variación ecogeográfica y morfológica de la culebra de pino mexicana. Se utilizó un total de 789 registros de ocurrencia y 20 variables climáticas y ambientales para evaluar el traslape, conservadurismo y divergencia de nichos ecológicos entre las cuatro provincias, utilizando un modelo de nicho ecológico (ENM) para cada una de ellas. La variabilidad morfológica se analizó mediante morfometría geométrica, lineal, escutelación y patrón de manchas negras de 262 ejemplares. Los resultados de la ENM indican que el área de distribución de P. deppei se subdivide en cuatro regiones bien definidas de idoneidad de hábitat asociadas al Altiplano Mexicano, la Faja Volcánica Trans-Mexicana, la Sierra Madre Oriental y la Sierra Madre Occidental, con zonas de contacto en sus límites. Estos resultados suponen un bajo solapamiento entre las cuatro provincias analizadas. El conservadurismo de nicho y la divergencia de nicho fueron apoyados por tres y dos comparaciones por pares, respectivamente. A nivel morfológico, la morfometría lineal, la escutelación y el patrón de manchas negras fueron los responsables de la variabilidad para discriminar los especímenes encontrados en la Faja Volcánica Trans-Mexicana respecto a las otras tres provincias. Como se esperaba, el patrón de variación en la forma de la cabeza consiste en estados de carácter bien definidos y exclusivos de cada una de las cuatro provincias donde habita P. deppei. Todas las comparaciones en los análisis multivariados de varianza de las configuraciones de los puntos de referencia con el CVA fueron estadísticamente significativas, y las tasas correctas de clasificación posterior fueron todas superiores al 35,5%. Finalmente, las variables ecogeográficas utilizadas muestran un reducido poder explicativo y predictivo de la variación de los caracteres morfológicos analizados. La variación morfológica en P. deppei podría ser el resultado de factores no considerados en el presente estudio, como diferencias en la ecología trófica, flujo genético limitado, variación no adaptativa o implicaciones filogeográficas. En este último caso, los resultados morfológicos obtenidos coinciden con un linaje meridional previamente reportado utilizando la configuración de haplotipos de las especies de P. deppei. Por último, nuestro enfoque morfométrico geométrico nos permitió analizar la variabilidad de la forma de la cabeza en P. deppei.

Urbanization increasingly threatens wildlife, as urban extent is expected to triple by 2030. However, the role of urbanization in population declines remains poorly understood for many species. To determine the role of urbanization in the decline of Woodland Box Turtles (Terrapene carolina carolina), we estimated abundances of box turtles via timed visual surveys at 11 forest patches along a gradient of urbanization in the rapidly urbanizing Piedmont ecoregion. We related abundance of female and male box turtles to landcover variables indicative of urbanization intensity (forest cover, impervious surface cover, and road density) quantified at three spatial extents (circular areas with a radius of 500 m, 1,500 m, and 2,500 m around each sampling area) to capture potential effects at the patch and landscape levels. Female abundance declined most strongly with increasing impervious surface area at a 500 m radius, and to a lesser extent with decreasing forest cover and increasing road density at a 500 m radius, with these variables explaining 42%, 31%, and 29% of the variation in abundance, respectively. Male abundance declined most strongly with decreasing forest cover at the 2,500 m and 500 m radii, but only 18% and 14% of the variation was accounted for by each of these variables, respectively. Observed negative associations between urban landcover and box turtle abundance suggest that urbanization contributes to their decline, especially in females. We advise that preserving or restoring large urban forest patches are important to the long-term persistence of Woodland Box Turtles in ever increasing urban landscapes.

Sternopygus sabaji, new species, is described from the Atlantic drainages of the Guiana Shield region of South America using traditional methods of morphometrics and meristics and microcomputed tomography (µCT) scans for osteological analysis. The new species is diagnosed from all other species of Sternopygus by the lack of dentition on the anteroventral surface of the endopterygoid and by the possession of a wider mouth. It further differs from its congeners by the following combination of characters: reduced humeral spot with low-contrast and poorly defined margins, possession of a light-colored mid-lateral stripe along posterior portion of lateral line, possession of 1–3 dark saddle-like markings along dorsum of smaller individuals, and a relatively low precaudal vertebrae count. This work provides the first description of a species of Sternopygus that is endemic to the Guiana Shield, joining S. astrabes and S. macrurus in elevating the species richness of the clade in that region to three species and the total number of valid Sternopygus to ten species.

Eurycea chamberlaini (Chamberlain's Dwarf Salamander) is a small spelerpine salamander with scant reproductive and life-history data available. Therefore, the objectives of our study were to examine the reproductive life history and population structure of E. chamberlaini from a North Carolina population. From February 2008 to February 2009, monthly collections were made in Craven County, North Carolina. All specimens (n = 392) were histologically examined for reproductive life history and population characteristics by month. Overall, male and female E. chamberlaini follow a reproductive cycle similar to other spelerpine species with sperm in the Wolffian ducts of specimens from September to February; however, spermatidogenesis was delayed until August and September with the presence of mature sperm in testes from August through November. We captured 201 female salamanders of which 36 were considered immature. We caught 191 males of which 27 were considered immature. The mean snout–vent length (SVL±1 SD) of mature females (27.13±2.33 mm) and males (25.84±2.03 mm) was statistically different from one another. Females tended to be larger than males from our monthly samples, with a greater proportion of the largest specimens being female. Overall, population structure of E. chamblerlaini appears similar to other coastal plain salamander species.

We explore the feeding habits of two populations of the lizard Aspidoscelis lineattissima from two localities (Cocinas = island and Xametla = mainland) under the hypothesis that in an insular environment, there is less selection of food, because it is a relatively comfortable environment to forage due to the presence of few competitors and predators. We also examine the predator–prey size relationship in this lizard species with the intention of distinguishing possible ontogenetic changes in the choice of prey sizes in the two localities. In stomach contents of the lizards from mainland, a total of 2,616 prey items were recorded, while on the island, 1,357 prey items were found. This number of prey was divided into 18 categories for the mainland and 20 for the island. In general terms, the most important prey in the diet of lizards from both localities were Isoptera, Coleoptera (adult and larvae), Araneae, Orthoptera, Hymenoptera (ants and others), Blattodea, and Diptera. Island lizards presented a greater amount of plant material in their stomach contents. The breadth of the food niche was greater on the island than on the mainland. Although statistically there were no differences regarding food overlap between localities, the highest overlap values between groups (age classes and sexes) were found on the mainland. We found a positive relationship between morphological variables of the lizards (snout–vent length, head width, and head length) with the maximum and mean values of the prey volume in both localities. This reveals an ontogenetic change that indicates that as lizards grow, they add a greater quantity of large prey to their diet and at the same time eat smaller prey. These results showed that the diet of the lizards from both localities was similar to other species of the genus. The feeding habits of a species in contrasting environments is evidence that is helpful for understanding the foraging patterns more clearly, and the possible connection with its life history characteristics, shedding more light on the hypothesis of niche amplitude and the optimal foraging theory.

Leaf litter is an important input to a variety of freshwater ecosystems. The species of leaf litter affects water chemistry, ecosystem processes, and the survival and growth of aquatic organisms. Given the potential fitness consequences, it is likely that aquatic organisms have preferences for aquatic habitats with particular species of leaf litter input. To investigate this, we placed shallow experimental pools at a field-forest edge in northern Louisiana, USA as potential sites for Cope's Gray Treefrog (Hyla chrysoscelis) oviposition with leaf litter from one of 14 different tree species in each pool. Tree species included 13 native trees and one invasive species, Bradford Pear (Pyrus calleryana). We measured the concentrations of tannins and 12 elements in leaf tissue, along with water quality and water depth in the pools. We used an information-theoretic approach and created different models to determine what variables best predict the number of treefrog eggs laid in each pool and thus may serve as a cue for female treefrogs during oviposition site selection. We found that tree species treatment was by far the best predictor of the number of eggs Cope's Gray Treefrogs laid in the pools. Treefrogs laid more eggs in pools with Post Oak and Sweetgum leaves and fewer eggs in pools with Southern Red Oak and Southern Magnolia leaves. It is unclear how female treefrogs are able to differentiate among these tree species or what cue they are using to make their choices. Our results highlight the importance of tree species to aquatic community assembly.

The pelagic larvae of coral reef fishes can detect and discriminate among different types of sounds suggesting that they may be able to localize acoustic cues and thus identify suitable settlement sites on reefs. It has been suggested that a description of ear development may provide clues about the importance of sound in larval behavior. Here we provide the first description of the ontogeny of the ear in the pelagic larvae and juveniles of representatives of three important families of coral reef fishes: Gobiidae (Elacatinus lori, E. colini), Apogonidae (Cheilodipterus quinquelineatus), and Pomacentridae (Amblyglyphidodon leucogaster, Amphiprion polymnus). Histological analysis revealed that the ear of the larvae and juveniles of the five study species lack any of the morphological specializations known in percomorph fishes. However, it showed that the ears of the two gobies are quite similar with respect to size and shape of the three otolithic organs, but that ears of the cardinalfish and damselfishes are different with respect to the absolute and relative sizes and position of the otolithic organs, as well as the timing of the appearance of the lagena; however, the functional significance of these features are unknown. It is concluded that if hearing plays a role in orientation behavior in the pelagic larvae of coral reef fishes then their “unremarkable” ears are sufficient to allow these diminutive fishes to carry out the extraordinary feat of navigating the open ocean and successfully locating coral reefs on which to settle.