With advances in genomic technologies, it has become increasingly feasible to generate large numbers of loci to address population genetic and phylogeographic questions. Nevertheless, many widespread and relatively abundant species remain unsampled using molecular approaches. The lined snake (Tropidoclonion lineatum), a semi-fossorial snake distributed across the Great Plains, is one such example. Despite the historical recognition of multiple subspecies based on noted variation in morphological characters, no formal molecular investigation of population structure has been conducted to date due to a paucity of vouchered genetic samples. Here, we present the first genomic assessment of range-wide population structure in T. lineatum using genome-wide single-nucleotide polymorphisms (SNPs) generated via triple-enzyme restriction site-associated DNA (3RAD) sequencing. Our results indicate largely continuous gene flow across the Great Plains, questioning the validity of the recognized subspecies. In contrast, populations at the northern range edge in South Dakota exhibit relative genetic homogeneity and modest differentiation from more southern populations, potentially reflecting recent isolation or increased genetic drift in peripheral habitats. Given the species’ endangered status in South Dakota, these findings highlight the conservation importance of range-edge populations while underscoring the need for denser, range-wide sampling—particularly in putatively disjunct regions—to fully characterize genetic diversity in T. lineatum. 

Probst T, Siler CD, Davis DR. 2026. Genomic investigation of population structure in a secretive, semi-fossorial snake (Colubridae: Tropidoclonion lineatum) across the Great Plains. Ecology and Evolution 16:e74431. [PDF]

Microbiomes are important to the ecology and evolution of their associated animal hosts. These important functions range broadly from individual animal health to population-level adaptations. Turtle-associated microbiomes are under increasing investigation, given turtles’ conservation status and the unique natural history of the shell as an evolutionary-developmental novelty. Many components of the turtle-microbiome interaction remain understudied, including how microbial communities assemble based on host and environmental factors. Here, we hypothesized that age, habitats, and body sites would exhibit significant differential effects on bacterial microbiomes in the Yellow Mud Turtle (Kinosternon flavescens) in the Chihuahuan Desert of west Texas, USA. We also hypothesized there would be differentialabundance of specificbacterial taxa associated with a recently described, algae-mediated shell disease. Using 16S rRNA amplicon sequencing of 64 turtle samples, we found bacterial community differencesamong body sites (cloaca, carapace, plastron, and skin), but weaker trends associated with habitat types (ephemeral or permanent-water ponds), and over age gradients (age 4–12+ years). Specifically,the carapace and plastron hosted high bacterial richness compared to the skin and cloaca, and all body sites differedin their bacterial composition across habitat sites. In many individuals, including those with advanced stages of the algae-mediated shell disease (Stage 3 or 4; 25% of sampled turtles), we detected significantdifferentialabundance of specificbacterial taxa, including Cyanobacteria strains. These results are important for informing sampling regimes in long-term studies related to K. flavescens ecology and evolution, and for continuing conservation and natural history work associated with turtles broadly.

Madison JD, Davis DR, Genter BW, LaDuc TJ, Muletz Wolz C. 2026. Microbiome varies by body site in the yellow mud turtle, Kinosternon flavescens, from the Chihuahuan Desert. Microbiology Spectrum 14:e03664-25. [PDF]

A new student-led note was recently published in Herpetological Review 56(3). MS student Kevin Green published a series of distributional records of the non-native Hemidactylus aff. malcolmsmithi from Mississippi and Louisiana, including the furthest north documented population in the USA, in northern Louisiana. This species is rapidly expanding its range across the southern USA, and will likely become the dominant Hemidactylus species at introduced localities. Congrats to Kevin on another publication!

Texas Tortoises (Gopherus berlandieri) are understudied compared to federally protected congeners. Despite important early studies on the basic ecology of G. berlandieri, quantitative identification of habitat associations with specific environmental conditions has been limited. Gopherus berlandieri inhabits Tamaulipan thornscrub across its range, and coastal populations are historically associated with low-relief clay ridges with thick mesquital scrub surrounded by salt prairie grasslands. Our study examined tortoise home range size and association with canopy cover and potential ground moisture at a protected natural area in Cameron County, TX, USA. Twelve tortoises were outfitted with GPS loggers that recorded location once an hour from March 2020 to March 2022. To delineate home ranges, we estimated utilization distributions (UDs) for tortoises as autocorrelated kernel density estimates (AKDEs) at low-use (95%) and core-use (50%) levels for each tortoise. UDs were estimated for the entire study period and during seasons of sustained heat or cold to determine if tortoises used space differently across these seasons over the study period. Applying a use-availability study design, we compared canopy cover and potential mesic ground condition (i.e., precipitation flow accumulation) within each tortoise’s UD (‘‘use’’) to the area within 1 day’s movement around the boundary of the UD (‘‘available’’). Tortoise UD sizes were significantly different across seasons for low-use (95%) but not for core-use (50%) AKDE levels. Tortoise UDs had greater canopy cover compared to available-but-unused areas at both AKDE levels. Potential mesic ground condition did not significantly differ between available and used areas. Our study revealed that tortoises vary the size of their home ranges throughout the year, whereas areas of intensive use or occupation tended to remain remarkably stable throughout the year. In seasons of extreme weather (hot or cold), tortoises seem to seek out areas of denser canopy cover that likely serve as thermal refugia. Based on our results, effective habitat identification may best be served by ensuring that canopy cover is at least equivalent to the values reported here to ensure sufficient refugia during extreme seasonal temperatures.

Guerra DA, Esque TC, Davis DR, Veech JA. 2025. Home range, seasonality, and the importance of canopy cover for Texas tortoises (Gopherus berlandieri). Herpetologica 81:224–235. [PDF]

Many amphibian species have declined throughout their ranges, and often the causes of those declines are poorly understood . Large-scale amphibian declines were first observed in the 1970s, and in the following decades, Batrachochytrium dendrobatidis (Bd) infection was determined as the cause of some of these declines . Retrospective studies allow us to evaluate historical disease patterns and are particularly valuable in species that are extirpated or extinct. The Black-spotted Newt (Notophthalmus meridionalis; Salamandridae) is an understudied species of salamander native to south Texas, USA, and northeastern Mexico that has shown alarming population declines over the past 70 years, most notably prior to 1980. Notophthalmus meridionalis has disappeared from the northern part of its range in recent decades. Multiple factors have likely contributed to its decline, including habitat loss, habitat fragmentation, and pesticide use. In the past century, the majority of native habitat in south Texas has been cleared for agriculture, urbanization, and roads, leaving small patches of fragmented habitat remaining across the species’ historical northern range. However, declines in N. meridionalis have also been observed in protected areas not affected by habitat loss and degradation. The reason for their disappearance from these areas is unknown, raising the question of whether Bd infections were contributing to their decline. Here, we assayed 314 N. meridionalis museum specimens to determine whether the historical presence of Bd may have contributed to population declines in this species.

Five new, short notes were recently published in Herpetological Review, most of which were written by student authors or have students as coauthors. Two of these notes were Natural History Notes documenting a new prey item and scavenging behavior in the Ornate Box Turtle (Terrapene ornata) (Davis and Davis 2024) and a new predator of the Plains Black-headed Snake (Tantilla nigriceps) (Summo Elias and Davis 2024). The other three notes were geographic distribution notes documenting the occurrence of three lizard species in three separate states. The first was a new county where Rough-tailed Geckos (Cyrtopodion scabrum) were found in Texas (Davis and Genter 2024), which only represents the second known county where this species occurs in the state (Davis and Genter 2024). Another note documented new distributional records of Common Wall Lizards (Podarcis muralis) in Indiana, which is also the first time they have been recorded in the state back after they were believed to have been eradicated (Mirtl et al. 2024). The final note was a formal documentation of the widely distributed (and rapidly spreading) Wood Slave (Hemidactylus mabouia) in Orange County, Florida (Summo Elias et al. 2024).

Shell studies of the Sonora Mud Turtle, Kinosternon sonoriense, have been limited except for a description of organisms living on the shell (Hulse 1976a) and a study on individual growth and morphometrics (Hulse 1976b), both involving individuals from Arizona, USA. Shell abnormalities in K. sonoriense were reported by Hulse (1976b) and included round pits up to 3-mm diameter in 26% of the specimens examined and a “corrugated carapace”, apparently due to “uneven deposition of additional bony material in the dermal skeleton” in 9% of the specimens examined. In his earlier paper, Hulse (1976a) reported epizoic algae, including Basicladia (now Arnoldiella) chelonum, on K. sonoriense in Arizona. While Hulse (1976b) noted that this alga could have been responsible for the pits, he rejected that conclusion because he observed many turtles with the algae present that lacked these pits. In the present work, we provide evidence for a similar shell-disease lesion progression throughout the range of K. sonoriense.

Christiansen JL, LaDuc TJ, Davis DR. 2024. Shell abnormalities in the Sonora mud turtle, Kinosternon sonoriense. Herpetological Review 55:193–198. [PDF]