Stephen C. Richter
Monitoring temporal changes in genetic diversity within populations can provide vital information on future viability. The dusky gopher frog, Lithobates sevosus, exists in isolation and previous research has shown that low genetic variability exists as a consequence of isolation and population size reduction. However, we do not understand how genetic variation has changed over time. Therefore, the objectives were to (1) determine temporal trends in population genetic variation and implications for long-term viability and (2) estimate effective population size. Egg samples collected from 1997–2014 were genotyped for nine microsatellite loci. Observed and expected heterozygosity, allelic richness, and Wright’s inbreeding coefficient were calculated and differences between sample years were assessed. Additionally, overall and pair-wise FST values were calculated to test for temporal genetic structuring. Effective population size was calculated using single-sample and temporal estimators. The results show a stable, but low, level of genetic variation over time, with no parameter suggesting significance over time. Weak genetic structure (FST = 0.023) was found among years, likely caused by increased effects of genetic drift in small populations. By our estimates, L. sevosus currently has an effective population size between 32.99–58.6 individuals. The ratios of effective population size estimates to census population sizes per year are fairly large (~0.5), which could possibly be explained by genetic compensation. Our research indicates the current management programs in place for L. sevovus have been effective at maintaining the genetic diversity present in the population; however, additional strategies need to be implemented to increase genetic diversity.