Conservation Status of the Plains Spotted Skunk, Spilogale putorius interrupta, in Texas, with an Assessment of Genetic Variability in the Species

Robert C. Dowler, Department of Biology at Angelo State University is the corresponding author, robert dot dowler at angelo dot eduIn this report, we present results of research on the conservation status of the plains spotted skunk (Spilogale putorius interrupta) in Texas and an assessment of the genetic variability in populations throughout the range of the species. The conservation status portion of the study included (1) mapping the species’ potential habitat in Texas using maximum entropy modeling (Maxent) with historic museum specimen records, (2) field-based surveying of locations in 10 counties to determine occurrence of the plains spotted skunk, (3) seeking additional occurrence records in Texas through crowd sourcing and citizen scientist approaches (4) using all current (2001 – 2017) occurrences to produce a model of probable geographic distribution in Texas and (5) assessing anthropogenic changes in land use, which may threaten the species’ habitats, by mapping current and forecasted oil and gas development and urbanization within the species’ modeled range. The species distribution model, combined with the land-change assessment, was used to select sites in 10 representative counties for field-based surveys in the hopes of revealing patterns of current distribution. Field surveys were carried out using live traps, enclosed track plates, and camera traps. These methods documented detections of plains spotted skunks (n = 12) in 4 of the 10 sites sampled. All methods of detection were successful, but cameras and live traps out-performed track plates. Crowd-sourced approaches and citizen scientist camera trapping revealed an additional 82 occurrences in the state, 79 of which were since 2009. These recent records were used to produce a species distribution model that provides relative probability of occurrence for the plains spotted skunk in the state. Our land-change mapping revealed potential anthropogenic threats to habitats at 2 of the sites (Katy Prairie and Fort Hood), which also had robust populations of plains spotted skunks based on 25 and 51detections, respectively). For our genetic assessment, samples of tissue from three sources (i.e., field surveys, state agencies throughout the distribution of the eastern spotted skunk, and museum tissue collections) allowed a detailed assessment of the genetic variability in the species (S. putorius) using both microsatellite markers and cytochrome b gene sequence. Our analysis of 119 specimens was able to establish that genetic patterns were consistent with currently accepted taxonomy of the 3 recognized subspecies of S. putorius (S. p. putorius, S. p. ambarvalis, and S. p. interrupta). We also determined that there was no evidence for hybridization with the congener, S. gracilis (western spotted skunk), a species co-occurring with the eastern spotted skunk in parts of Texas. The differentiation between S. p. putorius and S. p. ambarvalis was less pronounced (FST = 0.178; cytochrome b sequence divergence = 1.2%) than between these subspecies and the plains spotted skunk (average FST = 0.278; cytochrome b sequence divergence = 2.9%). Overall, genetic variability (observed heterozygosity = 0.474) in the plains spotted skunk was lower than that seen in common carnivores (striped skunks, raccoons), but slightly higher than some endangered carnivores (black-footed ferret). The heterozygosity levels more closely resemble the levels found within the island spotted skunk (S. gracilis amphiala) from the Channel Islands of California and other vertebrates that have a “threatened” conservation status. Key findings of the study include: 1) the current geographic distribution of the plains spotted skunk in Texas is reduced relative to historic records; 2) the species distribution model based on recorded occurrences since 2001 suggests areas of the state that are in need of further survey efforts; 3) genetic variability of plains spotted skunks is lower than more common carnivores, but higher than some recognized endangered species; 4) the subspecies, S. p. interrupta is a distinct genetic subunit of the eastern spotted skunk; and 5) continued energy development and especially future urbanization in some parts of Texas may affect populations of the plains spotted skunk.Texas Comptroller of Public AccountsBureau of Economic Geolog

Phylogenetic structure of Holbrookia lacerata (Cope 1880) (Squamata: Phrynosomatidae): one species or two?

Hibbitts, Toby J., Ryberg, Wade A., Harvey, Johanna A., Voelker, Gary, Lawing, A. Michelle, Adams, Connor S., Neuharth, Dalton B., Dittmer, Drew E., Duran, C. Michael, Wolaver, Brad D., Pierre, Jon Paul, Labay, Benjamin J., Laduc, Travis J. (2019): Phylogenetic structure of Holbrookia lacerata (Cope 1880) (Squamata: Phrynosomatidae): one species or two? Zootaxa 4619 (1): 139-154, DOI: 10.11646/zootaxa.4619.1.

Holbrookia subcaudalis

Holbrookia subcaudalis (Axtell 1956) Tamaulipan Spot-tailed Earless Lizard (Fig. 9) Holbrookia lacerata subcaudalis Axtell 1956 Holbrookia subcaudalis Hibbitts et al. 2019 (this study) Holotype. Texas Natural History Collection, University of Texas (TNHC 20000); collected by Ralph W. Axtell on 6 June 1955 in plowed field 4.8 miles east northeast of Bishop, Nueces County, Texas, USA (27º 36’ N; 97º 45’ W) at an elevation of 75 feet. Etymology. The name subcaudalis is derived from the latin word sub which means under or below and cauda which means tail. This refers to the dark spots on the underside of the tail in this species. Distribution. Holbrookia subcaudalis is composed of all populations south of the Balcones Escarpment in Texas and west to the Sierra Madre Oriental in Coahuila, Nuevo Leon, and Tamaulipas, Mexico. They are absent from areas with sandy soils. Diagnosis. Morphological description based on measurements and counts from 45 adults. This is a small, earless lizard with an average of 5 (1 – 10) black spots on the underside of the tail. The average snout-vent length (SVL) is 56 mm (31 – 72), paravertebral and dorsolateral body blotches are often separated. An average of 0.7 (0 – 6) blotches are fused out of an average of 6 (4 – 9) blotches. The blotches form four rows of transverse mostly circular blotches. The dark blotches on the rear legs are circular in shape and do not form into bands with the average number of leg blotches being 8 (4 – 14). Most individuals have black lateral spots on the abdomen and these average 2.6 (0 – 5). The average number of femoral pores on the left leg is 14 (10 – 19). The female body color is greenish yellow during the breeding season but they do not acquire orange on the throat in either sex.Published as part of Hibbitts, Toby J., Ryberg, Wade A., Harvey, Johanna A., Voelker, Gary, Lawing, A. Michelle, Adams, Connor S., Neuharth, Dalton B., Dittmer, Drew E., Duran, C. Michael, Wolaver, Brad D., Pierre, Jon Paul, Labay, Benjamin J. & Laduc, Travis J., 2019, Phylogenetic structure of Holbrookia lacerata (Cope 1880) (Squamata: Phrynosomatidae): one species or two?, pp. 139-154 in Zootaxa 4619 (1) on pages 148-149, DOI: 10.11646/zootaxa.4619.1.6, http://zenodo.org/record/324848