Date of Award

January 2015

Degree Type

Open Access Thesis

Document Type

Master Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Stephen C. Richter

Department Affiliation

Biological Sciences

Second Advisor

David M. Hayes

Department Affiliation

Biological Sciences

Third Advisor

Brad R. Ruhfel

Department Affiliation

Biological Sciences

Abstract

Monitoring temporal changes in genetic diversity within populations can provide vital information on future viability. The dusky gopher frog, Lithobates sevosus, exists in isolation with an estimated population size of 100-200 individuals, and previous research has shown that low genetic variability exists as a consequence of isolation and population size reduction. However, the temporal changes in genetic variation are not known. Therefore, my objectives were to (1) determine temporal trends in population genetic variation and implications for long-term viability of L. sevosus and (2) estimate effective population size. To accomplish these objectives, egg samples collected from 1997 to 2014 were genotyped for nine microsatellite loci. Observed and expected heterozygosity, allelic richness, and Wright's inbreeding coefficient were calculated for each year and differences between sample years were assessed. Additionally, overall and pair-wise FST values were calculated to test for temporal genetic structuring. To estimate effective population size, two single-sample estimators (Tallmon et al. 2008; Waples and Do 2008) and two temporal estimators (Waples 1989; Wang 2001) were used. The results show a stable, but low, level of genetic variation. Weak genetic structure (FST = 0.023 (95% CI 0.006-0.043)) was found among years, which can be attributed to the increased effects of genetic drift in small populations. L. sevosus currently has an estimated effective population size between 32.99-58.6 individuals. The ratios of effective size to census size per year are fairly large (~0.5) and exhibit an increasing trend over time, which could possibly be explained by genetic compensation--or the lessening of genetic variation reduction in times with low population numbers. This research indicates the current management programs in place for L. sevosus have been effective at maintaining the genetic diversity present in the population; however, additional strategies need to be implemented to increase genetic diversity.

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