Toby J. Hibbitts

Microhabitat sites provide important resources and thermal conditions to reptile species that can vary spatially and temporally. This study assessed Texas tortoise Gopherus berlandieri microhabitat use and its relationship with carapace temperature during their active (April–October) and inactive seasons (November–March) between January 2023 and February 2024 in a thornscrub savanna in southern Texas, USA. Other studies have examined Texas tortoise microhabitat associations during the active season, but none have assessed these associations during months when they are inactive, a period important to their survival throughout the year. To do this, we collected ground cover and overhead canopy cover data at locations of telemetered tortoises and paired random locations. We compared microhabitat variables by location type to determine if tortoises associated with certain cover types. Then, we assessed the relationship between microhabitat variables at tortoise locations and carapace temperature using linear mixed models. Results indicated that carapace temperature was most strongly influenced by hour of day year‐round and air temperature during the inactive season rather than associated microhabitat cover types year‐round. Tortoises associated with higher values of woody‐stemmed vegetation ground cover and overhead canopy cover than were available at random locations during both seasons. In addition to the importance of woody vegetation, the data suggest that tortoises most often used microhabitats with at least double the amount of grass and litter ground cover compared to other microhabitat variables. Managers prioritizing Texas tortoise conservation can use this information to manage vegetation to meet year‐round needs of tortoises by aiming for variety in vegetation cover with woody patches dispersed throughout the landscape. Our findings highlight the importance of considering spatial and temporal microhabitat components that affect reptile success, such as the thermal properties and composition of available cover types, in conservation efforts.

El Cantil de Tierra (Gerrhonotus infernalis) se distribuye desde la parte central del estado de Texas en los Estados Unidos, hasta la zona fronteriza del Noreste de México. La información ecológica publicada formalmente sobre sus patrones de movimiento tanto arbóreos como terrestres es muy escasa y con la finalidad de proveer información ecológica básica sobre las poblaciones existentes en la parte mas al norte de su rango de distribución natural, hemos utilizado radiotelemetria para analizar el área de distribución anual y la actividad arbórea de G. infernalis en Bamberger Ranch Preserve, en el condado de Blanco, Texas. De movimiento en G. infernalis fueron influenciados por señales ambientales (estaciones) y de comportamiento (periodo de reproducción), pero en términos generales, no se encontraron diferencias entre sexos. El rango anual de distribución espacial fue variable y los machos promediaron un mayor uso total del espacio, mientras que las hembras promediaron un uso mayor de sus áreas de preferencia, aunque dicha diferencia no fue significativa. Machos y hembras presentaron hábitos arbóreos similares, aunque vale destacar que la actividad arbórea presento variaciones estacionales y también durante el periodo diurno. La mayoría de la actividad arbórea ocurrió durante el verano y el fin de la primavera, mostrando una reducción en el final del otoño y el invierno. En promedio, G. infernalis utilizo sitios de percha más altos durante las últimas horas de la tarde y las primeras horas de la mañana. Los sitios de percha de menor elevación fueron utilizados durante las primeras horas de la tarde. Los resultados de esta investigación proveen información novedosa acerca de la ecología de la especie en la parte central del estado de Texas y favorecen el desarrollo de nuevas acciones de manejo para la especie.

The White Sands lizards of New Mexico are a rare and classic example of convergent evolution where three species have evolved blanched coloration on the white gypsum dunes. Until now, no geological replicate of the pattern had been described. However, one of the White Sands species, the lesser earless lizard (Holbrookia maculata), has been discovered to also inhabit the Salt Basin Dunes of Texas, where it has also evolved a blanched morph. We here present a first phenotypic and genetic description of the Salt Basin Dunes population of H. maculata. Phylogenetic inference based on a housekeeping gene (ND4) and a classic candidate gene in the melanin‐synthesis pathway (Melanocortin 1 Receptor; Mc1r) shows the newly discovered population as an independent lineage, with no evidence of genetic parallelism in the coding region of Mc1r. Initial morphological data suggest that while this population displays convergent evolution in blanched coloration, there are divergent patterns in limb length and habitat use behavior between the gypsum environments. Our findings present the White Sands/Salt Basin Dunes as an exceptionally promising comparative model for studies of adaptation and convergent evolution.

The western massasauga (Sistrurus tergeminus) is a small pit viper with an extensive geographic range, yet observations of this species are relatively rare. They persist in patchy and isolated populations, threatened by habitat destruction and fragmentation, mortality from vehicle collisions, and deliberate extermination. Changing climates may pose an additional stressor on the survival of isolated populations. Here, we evaluate historic, modern, and future geographic projections of suitable climate for S. tergeminus to outline shifts in their potential geographic distribution and inform current and future management. We used maximum entropy modeling to build multiple models of the potential geographic distribution of S. tergeminus. We evaluated the influence of five key decisions made during the modeling process on the resulting geographic projections of the potential distribution, allowing us to identify areas of model robustness and uncertainty. We evaluated models with the area under the receiver operating curve and true skill statistic. We retained 16 models to project both in the past and future multiple general circulation models. At the last glacial maximum, the potential geographic distribution associated with S. tergeminus occurrences had a stronghold in the southern part of its current range and extended further south into Mexico, but by the mid‐Holocene, its modeled potential distribution was similar to its present‐day potential distribution. Under future model projections, the potential distribution of S. tergeminus moves north, with the strongest northward trends predicted under a climate scenario increase of 8.5 W/m². Some southern populations of S. tergeminus have likely already been extirpated and will continue to be threatened by shifting availability of suitable climate, as they are already under threat from desertification of grasslands. Land use and habitat loss at the northern edge of the species range are likely to make it challenging for this species to track suitable climates northward over time.