Population and Conservation Genetics of Crawfish Frogs, Lithobates areolatus, at Their Northeastern Range Limit
Crawfish Frogs (Lithobates areolatus) are a North American ranid, considered near threatened globally with populations in decline throughout their range. We studied populations of Crawfish Frogs on local and regional scales at their northeastern range limit 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 regional level. We used 10 microsatellite loci to genotype frogs collected from three regional sites in Indiana separated by 50–172 km and at one of these sites within a network of three breeding ponds <1 km apart. Heterozygosity estimates revealed high levels of diversity within these populations (mean HO: 0.54–0.67 per site), which is encouraging for future management. The degree of population subdivision was low at the regional level (FST = 0.071 for sites within 172 km). Genetic differentiation was related to geographic distance between sampling sites, as predicted by an isolation-by-distance model. We observed no genetic differentiation between individuals sampled from ponds approximately 250 m apart and slight divergence of individuals from a pond approximately 750 m away. This suggests ponds within 1 km form a genetically distinct single breeding unit composed of multiple subpopulations. Finally, we observed high genetic differentiation between southwest and southeast Indiana sites indicating historical (rather than recent) isolation of these sites. These data will be applied to a regional management plan in an attempt to recover Crawfish Frogs along the northeastern extreme of their range.Abstract
Map of Indiana with localities of our three study sites: Hillenbrand Wildlife Management Area (Nate's Pond, Big Pond, and Cattail Pond), Dave's Pond, and Big Oaks National Wildlife Refuge (BONWR). Ponds sampled at each site are labeled by name.
Aerial image of three ponds sampled for Lithobates areolatus at Hillenbrand Fish and Wildlife Area, Indiana (Heemeyer et al., 2012).
(a) Genetic distance (FST/[1–FST]) plotted against geographic distance (km) for populations at ponds across all sampling sites. (b) Genetic distance (FST/[1–FST]) plotted against geographic distance (km) for Hillenbrand Fish and Wildlife Area ponds only. The solid line represents the best-fit linear regressions.
Results of analysis of population structure in Structure 2.3.2. Pond abbreviation codes are listed in Table 2.
Contributor Notes
Deceased.
