Mainland and Island Genetic Structure in Gopherus polyphemus

Gopher tortoises (Gopherus polyphemus) are a keystone species native to the Florida peninsula and its islands. They are considered a species of conservation concern across their range, but little is known about their population genetic structure and the conservation value of insular populations. Previous studies using a few molecular markers have identified genetic differentiation across the gopher tortoise's range and between neighboring mainland and island populations. Gopher tortoises are one of the most frequently translocated animals in the southeastern United States, so understanding their genetic structure is necessary to inform management strategies and ensure their continued health and survival. To investigate the population structure and genetic differentiation of gopher tortoises along Florida's Gulf Coast, blood samples from 144 individuals were taken from 10 sites in adjacent mainland-island pairs. DNA was sequenced and 129,344 single nucleotide polymorphisms (SNPs) were identified for genetic analysis. Genetic clustering analysis suggested three distinct groups, with populations clustering by latitude. Heterozygosity estimates ranged from 0.182 - 0.260 and inbreeding coefficients ranged from -0.018 - 0.039. Calculations of pairwise population differentiation, Fst, were highest between the four southern sites and lowest between the six northern sites. Three out of five of the island sites had a lower Fst value with their paired mainland site than any other location. Our data suggests that there may be regional genetic differences between gopher tortoise populations, and translocations should be carefully planned to prevent moving animals between regions which may compromise future adaptive potential.

For more information, contact Aryvelle Zaliauskas at aqzaliau@eckerd.edu