Population Genetics of the Big Bend Slider (Trachemys gaigeae gaigeae) and the Red Eared Slider (Trachemys scripta elegans) in the Contact Zone in the Lower Rio Grande Drainage of Texas




Schumacher, Lauren M.

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The red-eared slider (Trachemys scripta elegans) is well-known for its popularity in the pet trade. It is also known for its near cosmopolitan distribution, which is partly due to the release of these pet turtles. When introduced to a new area, non-native T. s. elegans can hybridize with other native Trachemys species. An example of this occurs between T. s. elegans and the Big Bend slider (T. gaigeae gaigeae) in western Texas. Recent research and trapping efforts have primarily focused on Big Bend National Park. Mitochondrial haplotypes unique to T. g. gaigeae have been observed in T. s. elegans inhabiting Rio Grande tributaries downstream of the park, which could indicate historical hybridization. This study sought to address these concerns by utilizing additional sampling within these areas. I used twenty polymorphic microsatellite loci and model-based clustering methods to detect hybrids. Out of the 120 turtles sampled, 7.5% were identified as hybrids using the program Structure v2.3.4, and 23.3% were identified as hybrids using NewHybrids v1.1. My results supported the findings of past research because hybridization was found between T. g. gaigeae and T. s. elegans. My results also supported the contention that morphology cannot be used to identify hybrids. Some of the backcrossed individuals were located in areas outside of the range of T. g. gaigeae. This may represent an ancestral polymorphism caused by previous gene flow between individuals in the Rio Grande, Pecos River, and Devils River.



Hybridization, Trachemys


Schumacher, L. M. (2015). Population genetics of the Big Bend Slider (Trachemys gaigeae gaigeae) and the Red Eared Slider (Trachemys scripta elegans) in the contact zone in the Lower Rio Grande drainage of Texas (Unpublished thesis). Texas State University, San Marcos, Texas.


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