The status of an introduced species (<i>Phrynosoma cornutum</i>) on barrier islands in South Carolina
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Introduced species can diverge from the source population when they become established in a new ecosystem. The Texas horned lizard (<i>Phrynosoma cornutum</i>) was introduced to the southeastern United States in the early to mid-1900’s. The species is native to the western U.S. where populations have been declining, but populations seem to be persistent on the South Carolina coast. This study examined three introduced lizard populations on Isle of Palms, Sullivan’s Island, and Edisto Beach in South Carolina and used morphology, diet, and genetic markers to determine divergence from western populations and among South Carolina populations. Data show that lizard diet, body size, and body shape significantly vary across introduced populations. South Carolina lizards generally followed the latitudinal trend for body size found in the native range, but were larger than the trend for some morphological measurements. Within South Carolina populations, females had greater snout-vent length than males at Isle of Palms and Edisto Beach, while juveniles from Sullivan’s Island had greater snout-vent length than those at Edisto. Body shape varied among lizards at the three study sites, with males and females from Sullivan’s Island having larger body parts for their size. Genetic analysis revealed that South Carolina populations have less variation than native populations, and south Texas is the likely source of the introduction. Diet differed between the introduced and native ranges as <i>P. cornutum</i> in South Carolina did not eat <i>Pogonomyrmex</i> harvester ants. The South Carolina diet was composed of ants (94.23%) with <i>Dorymyrmex</i> ants the most common prey, showing that harvester ants may not be critical for <i>P. cornutum</i> to persist as long as other ants are present. Learning more about introduced populations of <i>P. cornutum</i> and how they are able to survive may provide helpful insight into management and reestablishment of populations in the west.