Threatened across much of their range, Timber Rattlesnakes (Crotalus horridus) exhibit patterns of genetic diversity that are shaped by movement and aspects of their environment in ways that may foster or constrain conservation. We combine movement data with nuclear and mitochondrial population genetic data to understand the population structure and patterns of gene flow for snakes in four overwintering sites (hibernacula) in central Pennsylvania. Our analyses show that hibernacula separated by only a few kilometers can maintain genetic structure along with high gene flow. Female spatial use rarely overlapped with individuals from adjacent hibernacula, whereas male spatial use typically did overlap with individuals from adjacent hibernacula. This study offers new evidence for how asymmetry in gene flow (with males responsible for inter-hibernaculum matings) shapes Timber Rattlesnake population genetics.

A new species of Gigantactis is described from a single female collected from the eastern North Pacific. As with others of this genus, this species is distinguished by its unique luring apparatus, most obviously through the presence of a relatively short illicium, bearing a secondary escal-like appendage.

A new species of Nannocharax is described from the Luongo and Kalungwishi Rivers, tributaries of the Luapula River in the northeastern region of Zambia. The new species differs from its congeners by a combination of characters, such as the body coloration pattern formed by a series of one-scale-wide vertical bars, a small caudal-peduncle spot surrounded by a light clear area at the base of the middle caudal-fin rays, and a low number of scales in the circumpeduncular series and lateral line series. The new species is also distinguished from other members of the Nannocharax multifasciatus species-group by genetic distances ranging from 10.3% to 11.6% with DNA barcoding. Likewise, distance and coalescent molecular species delimitation approaches recovered the new species as an independent operational taxonomic unit. Newly generated hypotheses of phylogenetic relationships based on maximum likelihood and Bayesian inference for the new taxon are provided.

Species-level diversification (speciation) results from the evolution of reproductive isolation. When reproductive isolation is intrinsic (independent of ecological context), speciation is thought to be irreversible. Intrinsic reproductive isolation manifests as a reduction in hybrid fitness due to Dobzhansky-Muller incompatibilities, and can render hybrids sterile or inviable. During fieldwork in western Cuba, I identified abnormal-looking individuals with small gonads within an assemblage of Anolis. I hypothesized that such individuals were interspecific hybrids and predicted a phenotypic distinctness and lower reproductive fitness. I evaluated my predictions by comparing putative hybrids with candidate parental species in external phenotypic traits and gonadal indicators of reproductive fitness. I found that putative hybrids were phenotypically distinct and did not produce sperm cells, suggesting that hybrid sterility may be important in maintaining species boundaries in this ecologically complex system.

A new species of the hagfish genus Eptatretus (Myxinidae) is described based on a single female specimen, 296 mm total length, collected from the Bahamas, off southern Grand Bahama Island, Northwest Providence Channel, between depths of 560 and 591 m. The new species is distinguished from its congeners by having five pairs of well-spaced gill apertures arranged in a nearly straight line, a 3/2 multicusp pattern of teeth, 54 total tooth cusps, 18 prebranchial slime pores, 4–5 branchial pores, 47–49 trunk pores, 82–85 total pores, and two bilaterally symmetrical nasal-sinus papillae. We also discuss the taxonomy of a specimen from Suriname provisionally named as Eptatretus sp. by Shimizu. A distribution map and an updated identification key for all species of Eptatretus and Rubicundus from the western Atlantic are provided.

The Gopher Tortoise (Gopherus polyphemus) is a keystone species endemic to the Coastal Plain ecoregion of the southeastern United States. Gopher Tortoises excavate extensive burrows that are used by over 60 vertebrate and 300 invertebrate species. Our understanding of burrow commensals has generally been limited to Longleaf Pine (Pinus palustris) savanna and xeric uplands and shrublands, excluding private, working pine (Pinus spp.) forests that are known to harbor tortoise populations. Therefore, we used passive infrared wildlife cameras to document vertebrate burrow commensals and evaluate differences in composition across burrow classifications (i.e., abandoned, active, and inactive) within a private, working Loblolly Pine (Pinus taeda) forest located in the Upper Coastal Plain ecoregion of Georgia, USA. Our study showed that the composition of vertebrate commensals did not differ across abandoned, active, or inactive tortoise burrows, indicating that burrows, regardless of classification, may provide a similar suite of resources (e.g., refugia, forage) to vertebrate commensals. Also, we observed numerous species using burrows that typically occur in other landscapes with known tortoise populations (e.g., Longleaf Pine savannah). We encourage continued monitoring of tortoise burrows and other potential refugia within working forests to better understand how these structures contribute to species abundance and persistence within these forests.

The lack of demographic data for many protected species often means that threats are poorly understood during recovery planning, and this results in difficulty defining sufficient metrics for assessing progress on recovery actions. The Neuse River Waterdog (Necturus lewisi) is a federally protected aquatic salamander endemic to the Neuse and Tar-Pamlico River basins of central and eastern North Carolina. It has quietly declined during four decades of intense urbanization, but the specific drivers of decline are unclear because there are no demographic data and only limited detection/non-detection information available. Our first objective was to clarify the drivers of decline by synthesizing the current knowledge of the hypothesized threats to N. lewisi. Because preexisting demographic data are lacking, we used prior natural history research and studies of ecologically similar species to develop hypotheses for the observed declines in occurrence. Our second objective was to update the knowledge of the species' current distribution throughout its historical range and then test our hypothesized threats using new occurrence data. We conducted detection/non-detection surveys across 116 locations throughout the species' historical range in two consecutive winter seasons (2018–2019 and 2019–2020) and modeled the effects of local and landscape variables representing three broad threat categories (pollution, flow suppression, and land use/land cover) using an occupancy modeling approach. We fit models representing all biologically relevant combinations of variables simultaneously, recognizing that threats are not independent in their effect. Dominant substrate type was the best predictor of occurrence and was negatively associated with the transition from cobble to silt (P < 0.05). Our analysis most supported the hypothesis that observed declines in the occurrence of N. lewisi are a delayed result of sedimentation-induced recruitment limitation. Uncertainty in the mechanism of decline remains because recruitment limitation could not be directly estimated with two years of occurrence data, yet this interpretation gained through an understanding of the species' underlying biology and current distribution contributes to the knowledge about present threats and will help guide and evaluate future recovery actions for this protected and narrowly endemic aquatic species.

Humans have modified ecosystems around the globe. Due to such modifications, freshwater streams are experiencing shifts in thermal and hydrologic regimes. These changes are also linked to declines in the commonness and diversity of freshwater vertebrates. In particular, communities that occupy headwater streams are particularly sensitive to changes in hydrologic regimes that affect habitat availability and suitability for obligate (e.g., fishes) and facultatively aquatic organisms (e.g., salamanders). Ultimately, shifts in habitat suitability could affect interactions between these species to synergistically affect their ability to persist in headwater streams. This study used artificial stream mesocosms to investigate the interactive effects of flow variability and interspecific interactions of two common, headwater stream vertebrates: Black-bellied Salamanders (Desmognathus quadramaculatus) and Common Creek Chubs (Semotilus atromaculatus). Individuals were either paired with a conspecific or heterospecific (e.g., salamander or Common Creek Chub) and then crossed with one of three flow treatments: (1) high variability, (2) low variability, or (3) no variability. These results suggest that flow variability had no effect on intraspecific or interspecific competition. However, there was an effect of interspecific competition as salamanders decreased in body condition in the presence of Common Creek Chubs. Our findings suggest that these two common species have potentially adapted to variability in flow in their natural environment. Additionally, our results reinforce previous findings that Common Creek Chubs could play a role in the distribution of stream salamanders.

Anthropogenic disturbances are relatively common in freshwater systems; however, documenting and understanding disturbance-specific impacts on aquatic communities remains an area of needed focus. We examined the effects of wastewater treatment plant (WWTP) effluent on fish assemblage structure using 26 riffle sites positioned along two tributaries of the Niangua River, Missouri, USA (West Fork—WWTP effluent present, and East Fork—WWTP effluent absent). Comparisons of rarified species richness (i.e., using interpolation and extrapolation) indicated that α diversity was similar between forks, despite the West Fork having greater raw species richness. Multivariate analyses of fish assemblage structure (β diversity) revealed a significant difference between East and West Fork sites characterized by presence of Etheostoma flabellare (Fantail Darter) and greater abundances of Cottus bairdii (Mottled Sculpin), a heat-intolerant species, in East Fork sites. Analyses of abiotic site characteristics demonstrated that the West Fork generally contained smaller substrates and had warmer water temperatures during winter months, the latter of which may relate to WWTP effluent release in the upper West Fork. These results highlight significant structural differences between riffle fish assemblages in the presence and absence of WWTP effluent, suggesting effluent release may have localized and downstream impacts on stream community structure.

This report compares life histories and population ecologies of the miniaturized, terrestrial salamanders Desmognathus aeneus and Desmognathus wrighti in the southern Nantahala Mountains of southwestern North Carolina. The evaluation is a revision and extension of earlier studies of the species. The earlier field studies were carried out mainly from 1998 to 2001, with additional data collection through 2017. Growth curves and static life tables have been constructed from the earlier datasets. The life tables are snapshots of the population status of the two species during the sampling interval. I have included in the life tables columns that are based on parental and offspring body mass, in addition to the traditional columns based on number of individuals. It is assumed that the populations were in steady state during the sampling phases, under the premise of the equal fitness paradigm (EFP). The presence of a third species of Desmognathus, D. ocoee, in the forest habitats of the Nantahalas is seen as a complicating factor influencing the interaction of D. aeneus and D. wrighti. The results are discussed in the context of complementarity wherein two or more similar species having similar resource requirements reduce competition and persist together through differences in life-history strategies.

I describe courtship and mating of the plethodontid salamander Plethodon petraeus (Pigeon Mountain Salamander), which is a member of the P. glutinosus group (PGG) of eastern species of Plethodon (EP). Individuals exhibit adaptions for enhanced climbing ability and inhabit moist crevices of rock outcrops and cave openings within a very limited range in northwestern Georgia (USA). Courtship involves a unique blend of behaviors known for species in the PGG, P. cinereus group (PCG), and P. welleri group (PWG) of EP. Compared to most species in the PGG, there are notable differences during both the tail-straddling walk (TSW) and the period that precedes the TSW (‘pre-TSW phase’). Males exhibit both ‘foot dance’ and ‘foot shuffle.’ Frequent, high-amplitude mental-gland ‘popping’ by males during mental-gland sliding may be due to more-adhesive skin or mental-gland secretions. Olfactory delivery of pheromones is absent or rare because mental-gland contact to the female’s nares is absent or very infrequent during the pre-TSW phase and absent (or rare) during the TSW. Two forms of the duet behavior ‘female-first tail-straddling walk’ (ffTSW) occur during the pre-TSW phase: a discontinuous form during most courtships and a continuous form during some courtships. Infrequent ‘mouth grasping’ by males may be a facultative behavior that promotes transdermal pheromone delivery to less-receptive females. Very similar to some species in the PCG and PWG, the female initiates contact leading to the TSW in most courtships via turning back during ffTSW. If mating occurs within the protection of rock crevices, then reduced predation pressure or mate competition may have permitted the evolution of the relatively prolonged courtship (mean about 5 h). Results indicate that the detailed study of additional species will help refine current ideas about the evolution of courtship behavior in EP and perhaps other plethodontid clades.

We conducted a riverscape analysis of Rainbow Darters, Etheostoma caeruleum, across their range. We aimed to evaluate population genetic structure and diversity and to identify the possible drivers, contemporary or historical, that underlie the genetic patterns. This study genotyped 508 Rainbow Darters, collected from 67 locations across 23 river basins, at ten DNA microsatellite loci. Genetic clusters were assessed using STRUCTURE, Akaike information criteria (AIC), and discriminant analysis of principal components (DAPC). The STRUCTURE analysis identified two genetic clusters, one comprised of fish collected from more southerly sites and one comprised of fish from more northerly sites. Interestingly, the two clusters predominantly corresponded to sites that were either unglaciated or glaciated during the last glacial maximum (LGM). The AIC and DAPC identified additional structure, including one genetically distinct population in the Meramec River basin and another in the “Driftless” area of the upper Mississippi. Additional genetic clusters also occurred within the glaciated region, which may reflect expansion from different refugia or limited gene flow across river basins since the LGM. Our findings demonstrate the lasting legacy of glacial history on the contemporary genetic structure and diversity of a North American riverine species.

We describe a new species of fanged frog (genus Limnonectes) from the foothills of two, inland, south-to-north oriented, parallel mountain ranges of Luzon Island of the northern Philippines. Although the new species broadly co-occurs with its closest relative at numerous localities within the Luzon Pleistocene aggregate island complex faunal region, it can be readily diagnosed from Limnonectes macrocephalus based on its unpigmented (white) ventral surfaces of terminal digital discs, its unexpanded or minimally expanded terminal digital discs, and an allometric growth pattern indicating evidence of sexual dimorphism at a smaller overall body size. The new species, which can also be identified by its divergent 16S ribosomal RNA mitochondrial gene sequence, possesses a curious distribution unlike the range of any Philippine endemic amphibian characterized to date: it is known from nine interior (inland) localities distributed between the two, parallel, south-to-north mountain chains (the Cordillera and Sierra Madre) which characterize mainland Luzon. We interpret the presence of two broadly sympatric, genetically divergent, strongly supported haplotype clades—which correspond to morphologically diagnosable phenotypes, using traditional discrete characters and allometric growth patterns—as prima facia evidence of two, independently evolving evolutionary lineages (species) of giant fanged frogs on Luzon. The description of another new species of large-bodied fanged frog on Luzon from multiple localities in close proximity to the capital city (Manila) emphasizes the degree to which even well-studied larger Philippine landmasses possess unrecognized and overlooked biodiversity.

Éste es un homenaje a Héctor S. Espinosa-Pérez, por muchas décadas miembro de la Asociación Americana de Ictiólogos y Herpetólogos, y fundador y ex presidente de la Sociedad Ictiológica Mexicana, A.C. Uno de los ictiólogos mexicanos más notables de los últimos tiempos, Héctor falleció en la Ciudad de México el 20 de febrero de 2022, pocos días después de cumplir 68 años, dejando a su esposa y colega Patricia Fuentes-Mata y a sus hijos Héctor y Alejandro. Presentamos un panorama breve de su vida y obra, seguido de testimonios y anécdotas sobre su manera de ser seria, pero al mismo tiempo relajada y alegre.