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MOUNTAIN LION
ABSTRACT
Population connectivity is imperative to maintaining biodiversity and can bolster ecosystems and populations against disturbance and isolation. Connectivity and diversity are both decreasing on a global scale, hastened by increased anthropogenic processes including urbanization, unregulated harvest, and human-caused climate change. If connectivity remains impeded, landscapes can become fragmented, isolating and extirpating wildlife populations. These consequences often impact wildlife species with wide-ranging movement behaviors and low population densities, like large carnivores. Large carnivores in the Texas-Mexico border barrier system, a 132-km, 9-m-tall steel fence. This actively expanding geopolitical barrier has the potential to be an impermeable anthropogenic landscape feature for large-bodied wildlife species. Specifically, this potential loss of regional connectivity could further isolate the South Texas mountain lion (Puma concolor) population, calling into question long-term local population viability.
I investigated the potential effects of this anthropogenic barrier on the presence of mountain lions in South Texas. I also re-assessed the genetic status of transboundary-region mountain lion populations to better understand their genetic viability in the context of a changing landscape. For my first chapter, I used trail cameras to evaluate (1) if presence of the border barrier system impacted counts of mountain lions, and (2) if mountain lions were using available wildlife crossing structures at the base of the border barrier. I found that mountain lions had a 97% lower chance of being detected at barrier sites, and that no mountain lions used the wildlife crossing structures between July 2024 and September 2025. For my second chapter, I examined the genetic diversity and population structure of contemporary transboundary region mountain lion populations in Texas and New Mexico. I then compared the present-day (2022-2025) genetic samples to historical (1985-2010) samples to assess any change in population genetics over time. I used microsatellite genotypes from 142 mountain lions across Texas and New Mexico. I analyzed 109 historical samples from South Texas (n = 25), West Texas (n = 53), and New Mexico (n = 31), and 33 present-day samples from South Texas (n = 12), West Texas (n = 4), and New Mexico (n = 17). I estimated genetic diversity using expected heterozygosity (HE), observed heterozygosity (HO), mean allelic richness (Ar), and within population inbreeding (FIS).
I evaluated population genetic structure using pairwise FST and a Bayesian clustering algorithm in program STRUCTURE. I found increased genetic diversity (HE = 0.55, HO = 0.50, Ar = 2.84, nd FIS = 0.08) in the present-day South Texas lion population compared to its historical diversity (HE = 0.44, HO = 0.42, Ar = 2.45, and FIS = 0.07). I also found evidence of increased gene flow and decreased population structure among mountain lion populations in South Texas, West Texas, and New Mexico between the historical and present day periods. This research addressed critical knowledge gaps about an understudied large carnivore population within the context of a large, anthropogenic barrier, and provided insights into genetic impacts of changing regional connectivity.