Date of Award

January 2011

Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Stephen C. Richter

Department Affiliation

Biological Sciences

Abstract

Crawfish Frogs (Lithobates areolatus) are state endangered in Indiana and Iowa, with populations in decline throughout their range. I studied populations of Crawfish Frogs on local and statewide scales at their northeastern range limits to (1) assess the level of genetic diversity within populations (2) estimate fine-scale genetic structure, and (3) estimate genetic differentiation between populations at the state level. Crawfish Frogs breed in temporary pools and wetlands, and have high breeding-pond fidelity; therefore I predicted to find genetic differences between ponds at small geographic scales. I used 10 microsatellite loci to genotype frogs collected from three primary populations in southeast and southwest Indiana, with distances between sites ranging from 0.29 km to 172 km. Heterozygosity estimates revealed high diversity in these populations (mean Ho: 0.54 to 0.67 per site), which is encouraging for future management. The degree of population subdivision was low at the state level (FST = 0.071), with little evidence for genetic structure at a fine scale (FST = 0.008 for ponds within 1 km). Genetic differentiation was explained by geographic distance between sampling sites, as predicted by an isolation-by-distance model. I observed no genetic differentiation between individuals sampled from ponds ca. 250 m apart, and slight divergence of individuals from a pond ca. 750 m away. This suggests ponds < 1 km from each other form a genetically distinct single breeding unit, made up of multiple subpopulations. Finally, I observed high genetic differentiation between southwest and southeast Indiana populations indicating historical (rather than recent) isolation of these populations. Further research is needed to determine the minimum distance at which populations become distinct.

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