Conservation Genetics of Texas Horned Lizards (Phrynosoma cornutum)

Williams, Dean A.

Hale, Amanda M.

Wall, Ashley E

Biffi, Daniella

Department of Biology

Texas Christian University

Fort Worth, TX

The Texas horned lizard (Phrynosoma cornutum) has experienced declines in the state of Texas due to habitat loss and the introduction of invasive red fire ants (Solenopsis invicta). We conducted a population genetics study to aid in future reintroduction and captive breeding initiatives in Texas. We used 11 nuclear microsatellite loci to genotype 707 individuals. Bayesian clustering of multilocus nuclear genotypes indicated the presence of three population clusters that correspond to 1) South Texas Plains and Coastal Prairie ecosystems, 2) High Plains, Rolling Plains, Edwards Plateau, and Pecos ecoregions, and 3) Chihuahua Desert ecoregion. Sequencing a subset of individuals at the mitochondrial NADH dehydrogenase subunit 4 (ND4) region revealed a strong genetic break between the Chihuahua Desert ecoregion and the other two genetic clusters as does the entire data set when sequenced at the mitochondrial d-loop region. Genetic diversity is high in protected areas but is significantly lower in populations that occur in small towns. Towns act as islands, isolating lizards from surrounding populations, resulting in low genetic diversity and low effective population size (Ne). A detailed study within a small town revealed restricted home ranges (usually within a town block), rare movement across roads, and significant genetic structuring on either side of major roads suggesting these roads serve as barriers to gene flow. Although data on local adaptation are currently lacking, we suggest the correspondence between genetic structure and major ecoregions warrants a cautionary approach to translocation and captive breeding strategies. Captive-bred Texas horned lizards should only be repatriated to their region of origin and translocations should only occur within the three major genetic clusters. Lizards located in small towns should not be used in captive breeding programs or in translocations due to their lower genetic diversity.