In the late 1940s, Rio Grande Sucker Pantosteus plebeius was reported in tributaries of the Gila River in the Colorado Basin and presumed to be introduced because of its absence in mid-19^th century surveys. We assayed genetic variation at ten microsatellite loci and two mtDNA genes (cyt b and ND4) to test the hypothesis of human-mediated introduction into the Gila within the last century. Phylogeographic analysis indicated that Gila River populations shared recent common ancestry with populations in the Mimbres River. Using approximate Bayesian computation (ABC), we rejected the hypothesis that Rio Grande Sucker was introduced to the upper Gila River within the last century. Rather, we hypothesize an older (∼4000 years before present) headwater capture event that facilitated transfer of fishes from the Mimbres to Sapillo Creek in the Gila Basin. From there, suckers dispersed to the San Francisco River and became established in upland stream habitats. Rio Grande Sucker exhibits low levels (<10%) of introgression with Desert Sucker but maintains species cohesion in the Gila Basin. We conclude that Rio Grande Sucker is native to the Gila Basin, and that these populations harbor unique diversity that could play an important role in species conservation. More generally, rigorous testing for human-mediated translocation is a difficult analytical problem, but a definitive means to do so is essential to fully understand the biogeography of freshwater fishes of the American Southwest.

Horned lizards, Phrynosoma spp., and harvester ants, Pogonomyrmex spp., could be in a predator–prey arms race in which the lizards are specialists that feed on harvester ants, and ants have highly toxic venom and other defenses to help deter predacious horned lizards. All 23 examined species of harvester ants possess venoms that are highly lethal to mice, but the venoms of the tested ant species were nearly inactive toward horned lizards. Blood plasma of Phrynosoma cornutum contains a factor (or factors) that neutralizes the ability of harvester ant venom to kill mice, but does not neutralize the venoms of honeybees, a rattlesnake, Russell's viper, or a cobra. A species of harvester ant present only in southern South America was used to test the predictions that the lethality of harvester ant venom evolved in response to predation pressure from horned lizards, and that horned lizard plasma does not neutralize the lethality of this species of harvester ant. This ant species did not overlap in range with horned lizards, which have a range from Guatemala to Canada. Not only was the venom of the South American ant species the most lethal of all tested harvester ant venoms, the venom's lethal activity was neutralized by horned lizard plasma. These results indicate that horned lizards responded to the lethality of their invertebrate prey's venom, but that the harvester ant venom lethality did not evolve in response to predation pressures by present day horned lizards.

Internal implantation of radio-transmitters is the preferred attachment technique for snakes, but the high costs and invasive nature of the surgery make a functional alternative desirable. Attaching radio-transmitters externally can be a cost-effective alternative to surgical implantation. External transmitter attachment site and methodology depend on the unique morphology of a given study species, making external adherence impractical for most snake species. Rattlesnake rattles are unique morphological features that can serve as an attachment site for external radiotransmitters. From 2011 to present, we have been attaching transmitters to the rattles of Eastern Diamondback Rattlesnakes (Crotalus adamanteus; EDB) using thread and epoxy. We calculated average monitoring duration using radio-telemetry data collected from 49 adult EDBs telemetered from 2014 to 2017 in coastal South Carolina. On average, we monitored EDBs for 189±78 days with 14 EDBs monitored >240 days and 3 EDBs monitored >300 days. External transmitter attachment is a viable alternative to surgical implantation, providing a noninvasive approach to monitoring rattlesnakes.

The systematic importance of larval characters of the Neotropical genus Proceratophrys has been demonstrated. We review the internal anatomy of the tadpoles of the monophyletic P. bigibbosa species group, provide the first description of larval musculature and new data on the chondrocranial morphology, and describe the external morphology and buccopharyngeal anatomy of the tadpole of P. brauni. Our results support four larval synapomorphies for the P. bigibbosa species group (i.e., conical vent tube, dorsal fin originating in the body-tail junction, large gap on the second upper tooth row, and trapezoid median ridge on the buccal roof). The presence of a chondrified commissura quadrato-orbitalis, the processus pseudopterygoideus, and an enlarged element on the posterior margin of the hypobranchial plate near the attachment of ceratobranchial IV could be putative synapomorphies for Odontophrynidae.

Despite the widespread occurrence of myrmecophagy in anurans, it is unclear whether ant-specialists feed on ants opportunistically or whether they prefer species with specific morphological, ecological, or nutritional traits. We flushed 105 stomachs of a lowland neotropical toad, Rhinella alata, and identified each consumed ant to species level. We calculated linear selectivity to determine predator preference for ants by comparing the abundances of consumed species to their relative abundances in the leaf litter community on Barro Colorado Island, Panama. We conducted linear regression models to test whether linear selectivity or general predator preference related to seven morphological characteristics and two measurements of nutritional content. Rhinella alata preferentially ate 24 ant species. Other species were either avoided (n = 34) or were eaten opportunistically (n = 26). Preferred ant species were large and textured with hair and/or rugosity. We found that prey preference did not relate to prey nutritional content, that small ants were avoided even if they were superabundant in the environment, and that chemically defended and aggressive ants were preferred if they were large enough. We propose that R. alata prefers large ants because they represent a more efficient prey item in terms of prey handling time and because they are easier to see than are smaller ants. Furthermore, we hypothesize that predation attempts are more successful when prey are textured because microstructures on the tongue and prey surface may increase prey adhesion. The ant specialist R. alata is not specializing on any particular ant species but rather maximizing prey quantity over quality by only eating the largest ants, despite their scarcity in the environment.

A new species of Pristella is described from the Río Meta drainage, Río Orinoco basin, Colombia. Pristella ariporo, new species, is described as the second known species of the genus and differs from P. maxillaris by lacking maxillary teeth, possessing all teeth of premaxilla and dentary conical, by the absence of a dark blotch on the pelvic fin and the absence of a humeral blotch. The evaluation of the relationships of the new taxon within Characidae through an extensive phylogenetic analysis recovered Pristella as a monophyletic clade, sister to Bryconella pallidifrons. A new diagnosis of Pristella is provided. Hyphessobrycon axelrodi, the only species of this genus possessing only conical teeth, may actually be a species of Pristella.

Developing an understanding of life history of a rare species is vital to formulating conservation strategies for its management and protection. Current knowledge about Noturus stanauli, the Pygmy Madtom, includes morphology, scant distribution data, and genetic analysis between populations in the Clinch and Duck rivers. In this study, we assembled a list of standard (SL) and total (TL) lengths for 45 individuals from our observations, museum records, and agency reports. Results using TL indicate two age classes (young-of-the-year and adult) throughout the year, a spawning period in late June–late August, and maximum longevity of approximately 1.5 years. In our collections, lengths ranged from 14–42 mm TL (n = 41), with a mean of 30.5 mm TL.

A new guitarfish of the genus Pseudobatos is described based on 82 specimens obtained from the Gulf of California. Sixty-three morphometric measurements were taken on all specimens, and on ten specimens from each of three congeners. A principal component analysis and linear discriminant analysis were performed on these morphometric data for discrimination. The new species (∼685 mm TL) is most similar to Pseudobatos productus but differs in having a narrower maximum disc width (30–35% vs. 36–38% TL), shorter distance from nostril to disc margin (2.8–4.0% vs. 4.2–5.2% TL), narrower disc width at anterior orbit (12–19% vs. 20–22% TL), and a narrower tip of snout width (3% vs. 4–6% TL). The species is also less densely scaled between the orbits and has less pronounced rostral thorns than Pseudobatos productus. A key to the guitarfishes of the Gulf of California is also provided.

Examination of contemporary (ecological) and historical (evolutionary) relationships within fish assemblages may provide understanding of the relative influences of competitive exclusion and habitat filtering assembly mechanisms. However, interpretation of relationship patterns (e.g., even or clustered) must consider niche conservatism, ecological convergence, abundance weighting, and spatial scale for proper understanding. The goals of this study were to identify influences of habitat filtering and competitive exclusion assembly mechanisms in darter (Percidae: Etheostomatinae) assemblages in the Duck River, Tennessee, and to build a conceptual framework describing the intricacies of assembly within this species-rich system. Phylogenetic relatedness, abundance weighting, habitat use similarity, functional morphological relatedness, and niche conservatism (for habitat use and morphology) were quantified for 15 darter assemblages along the stream gradient to elucidate magnitude and progression of assembly mechanisms. Habitat filtering was identified as a primary contributor to assembly based on findings of phylogenetic clustering and consistent co-occurrence of species that shared similar habitat requirements. Morever, lack of habitat use conservatism suggested that darters of two clades (both well represented in assemblages of the study) have converged on similar habitat needs in the system. Competitive interactions may have followed the initial habitat filter, as demonstrated by limiting morphological similarity within assemblages. This study demonstrates the importance of accounting for contemporary and historical factors to identify magnitude and progression of assembly mechanisms in fish assemblages. Furthermore, this study builds upon previous darter assembly work and provides a novel illustration of how habitat use convergence between phylogenetic clades can alter interpretations of assembly mechanisms in species-rich communities.

In many animal species, adult females and males often differ in characteristics other than primary sexual traits. Thus, body size tends to be related to reproductive success through different pathways in females and males, sex-specific foraging or dispersal strategies, and/or adaptations to reduce intersexual trophic competition. As result of these differences, the body size that conveys maximal fitness often differs between the sexes, favoring the evolution of sexual size dimorphism. In this study, we use an allometric approach to evaluate the changes in magnitude of sexual dimorphism in a population of Sceloporus formosus. Allometry refers to the relationships observed between body size and other organismal traits. Natural and sexual selection on morphological traits may modify allometric relationships. Traits under selection can show positive allometry, with slopes steeper than 1 (hyperallometry). We performed allometric major axis regressions of seven morphological traits on the snout–vent length, a standard measure used as a proxy for lizard size. The major axis regressions of female trunk length and width, and male trunk length showed hyperallometric slopes, suggesting that in S. formosus these traits could be under natural selection.

Two new species of the suckermouth armored catfish genus Baryancistrus are described from the Jari River basin, at the border of Pará and Amapá states, Brazil. The new species are the first representatives of the genus described from rivers draining the Guiana shield, and can be distinguished from their congeners by color pattern and a combination of nonexclusive characters. Baryancistrus micropunctatus, new species, has a color pattern similar to B. longipinnis from the Tocantins River, whereas Baryancistrus hadrostomus, new species, has a color pattern that is unique for the genus, with a gray to black body covered by small and widely spaced white points. The first exemplars of the two new species were collected in the late 1980s by INPA ichthyological staff, and in 2007 additional materials were collected by the Museu de Zoologia da Universidade de São Paulo (MZUSP), providing a foundation for this description of the new species.

Long-term studies on wildlife populations are necessary to track population abundance and shifts in demography over time, yet such studies are difficult to plan, fund, and conduct and are therefore rarely undertaken. Such studies are especially important for long-lived species that can persist for long periods of time with little to no reproductive output or recruitment. We conducted two population studies spanning a 30-year time frame on the globally endangered Spotted Turtle (Clemmys guttata) on protected land in the center of their range. Spotted Turtles are endangered in Canada, listed as globally endangered on the IUCN red list, and declining throughout their range. However, there has only been one previous long-term study tracking their long-term population trajectory. Here, we use mark–recapture data collected over a 30-year time frame and report that the estimated population size of Spotted Turtles has decreased by 49% at our study site despite the habitat residing with a protected area. This decline was concurrent with a significant increase in the proportion of larger individuals within the population, indicating a lack of recruitment into the sub-adult stage class. These results highlight the value of long-term studies in monitoring population changes of long-lived species, the importance of active management within protected areas, and the ability of long-lived species to persist for long periods of time despite having little recruitment and a declining population trajectory.

Genetic polyandry was assessed in 27 litters of Blacknose Shark (Carcharhinus acronotus) from genetically distinct populations in the U.S. Atlantic (19 litters) and eastern Gulf of Mexico (eight litters) using 23 polymorphic microsatellite loci. Two methods were used to estimate genetic polyandry, and the overall observed rates were high (74% COLONY2; 81% allele counting method), with a maximum of four sires detected in a single litter. When separated by region, the rate of genetic polyandry was 63% (COLONY2) or 74% (allele counting method) in the U.S. Atlantic, and 100% (both methods) in the eastern Gulf of Mexico. Data were resampled to evaluate how the number and diversity of markers analyzed affected the estimated rate of genetic polyandry. The number of alleles per locus had a dramatic effect on the detection of polyandry, with a difference of 56% in the estimated rate of genetic polyandry (22% vs. 78%), when using only the five loci with the highest diversity (A = 21–44) versus lowest diversity (A = 3–5). The total number of markers assessed also affected the estimated rate of genetic polyandry, and the estimated rate increased by 13% when using 10 versus 20 loci (66% vs. 79%, respectively). These results suggest that unless loci are highly polymorphic, relatively large numbers of loci are required to estimate the rate of genetic polyandry accurately in elasmobranchs, particularly those with small litter sizes like the Blacknose Shark.

Anuran vocalization is one of the most energetically expensive behaviors recorded in vertebrates. To sustain this behavior, circulating hormones in male frogs must act to promote calling behavior while mobilizing energy reserves. We hypothesize that this is accomplished through the actions of testosterone (T) and corticosterone (CORT). T is thought to elicit calling, while CORT mobilizes energy reserves. Eventually, high CORT concentrations and low energy reserves suppress calling behavior. We evaluated this hypothesis in light of the reproductive ecology of the Pig Frog, Lithobates grylio. Plasma samples from calling and non-calling males were collected during four months of the reproductive season. Calling males were shown to have significantly higher concentrations of circulating T and high body conditions. Conversely, non-callers exhibited elevated CORT and low body conditions. There was no correlation between the two hormones, but circulating T concentrations did decrease over the season. Lastly, we found that CORT is positively correlated with circulating glucose (in non-callers); this finding is supported by CORT's known role in gluconeogenesis. Taken together, these data indicate that circulating hormones and available energy reserves likely influence calling behavior in L. grylio.

The freshwater crocodile inhabiting Papua New Guinea, currently recognized as Crocodylus novaeguineae, exhibits morphological, molecular, and ecological divergence between the northern and southern versants of the Central Highlands and occupies separate evolutionary trajectories. A robust body of work has long encouraged the formal description of New Guinea crocodiles from the southern versant of the highlands as a distinct lineage with a taxonomy that reflects diagnosed relationships. Here, we use geometric morphometric techniques to assess cranial shape variation between specimens from both versants and add to the diagnostic evidence supporting a more accurate taxonomy. Further, herein, we formally describe the southern variant as a distinct lineage (Hall's New Guinea Crocodile; Crocodylus halli, new species).

The Zebra Shark, in recent years known as Stegostoma fasciatum (Hermann, 1783), is well known for its dramatic ontogenetic change of color pattern, from striped (“zebra”) juveniles to spotted (“leopard”) adults. Nevertheless, many aspects of the species' biology, ecology, and morphology are still unknown or inadequately described, and its nomenclature is contentious. This study introduces a hitherto undescribed color morph of the Zebra Shark and provides an updated diagnosis and redescription of the species. Firstly, we establish that the Zebra Shark remains a single species based on genetic data from mitochondrial COI and ND4 markers. Secondly, through morphological analyses, we conclude that there are two morphs of the species, the known, zebra striped morph and a new, sandy colored morph. Both morphs were studied morphometrically to expose any ontogenetic changes, such as a decrease in the relative length of the tail with increasing total length (TL). The external coloration pattern clearly differentiates the two morphs, and both morphs can be further divided into three stages based on color pattern and size: juveniles (255–562 mm TL), transitionals (562–1395 mm TL), and adults (>1300 mm TL). The transitional sandy morph is dorsally covered by a swirly pattern of thin, dark brown bands edged with freckle-like brown spots. The adults are a uniform sandy beige, partially covered with brown freckles. A mature male of the zebra morph displayed a yet unknown feature of the claspers: a small, triangular spike extruding from the dorsal terminal of the clasper glands. Finally, we reviewed the nomenclature of the species and suggest that the original name Stegostoma tigrinumForster, 1781 should be used as the senior synonym for the species.

The diet of lizards is associated with environmental variables, food availability, and morphological traits. This study evaluated the diet as well as sexual dimorphism in head structures and its relationship with prey volumes in males and females of two populations (Las Lagunas and El Oro, San Luis Potosí, Mexico) of the polymorphic Minor Lizard, Sceloporus minor. The diet is composed of 16 prey categories in addition to plant material. The family Formicidae, flying Formicidae, and the orders Coleoptera, Hemiptera, Lepidoptera, and Orthoptera represent the highest values of food importance by sex and population. In both populations, plant material was observed as part of the stomach contents. The results showed a high food niche overlap between sexes and populations, as well as low food niche amplitude. The Las Lagunas population showed sexual dimorphism in the dimensions of structures associated with the head, males being larger than females. However, the population from El Oro did not show sexual dimorphism in any of the variables analyzed. No correlation was found between prey volume and morphological variables associated with the head in either of the two populations. The results showed that the diet of the lizards in these two populations is similar to that recorded for other species of the genus. The lack of correlation between prey volume and head structures indicated that diet does not explain the presence or absence of sexual dimorphism in these populations. Therefore, it could be explained by other characteristics involved in sexual selection, such as color pattern, competition for territory, or the use of different microhabitats by the sexes. A large number of studies that analyze body shape, behavior, and use of microhabitat consider that temporal and spatial factors could help determine the reasons that contribute to ecological and morphological variations between populations of S. minor.

Phenotypic variation within a species can be associated with genetic differentiation and varying environmental conditions among populations and their habitats. The relationship between environmental conditions and phenotype expression can influence evolutionary potential, possibly affecting rates of speciation or ecological character displacement. Here, we use a geometric morphometric approach to investigate if shell-shape morphology variation is influenced by the location within the drainage basin (cumulative drainage area) in a freshwater turtle, Graptemys nigrinoda. Drainage area is used due to its hierarchical controls on hydrology, channel morphology, and thus instream hydraulics that comprise the physical habitat hypothesized to drive differences in shell morphology. In addition, we investigate the extent to which salinity may drive similar morphological variation in coastal range extents. We use spatial regression models to assess how geographic variation in carapace length and shell height is influenced by cumulative drainage area and marsh habitat type (i.e., freshwater or brackish marsh). We found that carapace length, shell height, and carapace shape variation covaried with cumulative drainage area in both sexes. Shells become larger and more domed with larger cumulative drainage areas. Additionally, turtles from larger cumulative drainage areas are characterized by distal shifts in costal and marginal scute orientation and medial shifts in costal scutes. The morphological response to hydrogeomorphic controls on physical habitat (e.g., channel morphology and hydrodynamics) as represented through drainage area is predictable and reported in several turtle species. Although others have invoked a predator response hypothesis for larger, more domed shell phenotype (i.e., stronger shell to resist crushing), we propose an alternative hypothesis that there is a potential locomotive advantage of a domed shell phenotype in lentic habitats likely related to buoyancy (i.e., greater volume to mass ratio), which needs further research. Furthermore, increased body size could likely be a selective advantage for inhabiting resource-rich brackish water habitats with increasing dietary diversity. Because these phenotypes (flattened shell and large body size) are associated with locomotion efficiency, our results suggest that gene flow is potentially impeded by distinctly different environmental conditions, providing further evidence for continued or maintained divergence between suggested subspecies within Graptemys nigrinoda.

Genome sizes (expressed as C-values, or haploid genome sizes) of six species of Honduran plethodontid salamanders (one species of Nototriton and five of Bolitoglossa) vary greatly. Nototriton has a moderate-sized genome (29.2 pg) relative to other species of salamanders. Genome sizes in the species of Bolitoglossa span a range of 24 pg (∼23.4 gigabases) of DNA and include the largest genomes (83.7 pg) reported for the genus and for the family Plethodontidae. A phylogenetic analysis indicates that genome evolution in this group of salamanders featured mainly large increases in the mass of nuclear DNA. We propose that these evolutionary changes in genome size reflect random drift in small, isolated populations in the highlands of Central America.

We investigated the roles of ecological and historical factors on the phylogenetic structure and spatial and trophic niches of anurans in Caatinga and Atlantic Forest in the Brazilian Northeast Region. We sampled specimens and ecological data using both active search and pitfall traps to sample sites for 15 days during dry and wet seasons. Assemblages from Caatinga were more structured on dietary niche than those from Atlantic Forest. Ecological factors had a higher effect on the trophic niche than on the spatial niche but were lower than historical factors, thus indicating past adaptations. The onset of the dry season usually increases the dietary structure of assemblages. Water restrictions in Caatinga affected prey abundance, increasing niche segregation. Differences between environments indicated that local factors exerted greater influence in Caatinga. We did not observe spatial niche structure in most assemblages, regardless of the environment, and we found strong evidence of niche conservatism in all assemblages. Phylogenetic effects detected in spatial niches reinforce the separation between arboreal and terrestrial/semi-aquatic lineages during the Cretaceous. Lastly, no niche complementarity was detected, despite the different structure patterns. No assemblage was phylogenetically structured, and the existence of a possible “ecological filter” in Caatinga did not lead to increased “phylogenetic clustering” in this environment.