Metapopulation Connectivity in Voles (Microtus sp.) as a Gauge for Tallgrass Prairie Restoration in Midwestern North America

Abstract

Applying quantifiable metrics to validate the success of restoration efforts is crucial for ongoing management programs in anthropogenically fragmented habitats. Estimates of dispersal can provide such baseline data because they measure not only the extent to which restored patches are colonized and interconnected, but also their metapopulation source/sink dynamics. In this context, we estimated dispersal and population connectivity among prairie (Microtus ochrogaster; N=231) and meadow vole (M. pennsylvanicus; N=83), sampled from eight restored plots at five tallgrass prairie sites embedded within the agricultural matrix of midwestern North America. Our expectation was that extensive distances separating these restored habitats (i.e., 48-246 km) would spatially isolate vole metapopulations, resulting in significant genetic differentiation. We first used molecular taxonomy to validate the field-identifications of all sampled individuals, then used pairwise FST derived from 15 microsatellite DNA loci to estimate genetic connectivity among the species-delimited study populations. Metapopulation stability was gauged by assessing migration rates and deriving effective population sizes (Ne). We also calculated relatedness values (r) as a potential surrogate for contact in prairie vole, a primary vector for Lyme disease. Molecular species-assignments contravened field-identifications in 25% of samples (11 prairie/67 meadow) and identified two instances of species-hybridization (0.6%). Local effects (i.e., population crash/drought) were manifested at two sites, as documented by significant temporal declines in Ne and r. Overall, high migration rates and non-significant (10/15) pairwise FST values underscored elevated metapopulation connectivity. A single site that recorded five significant FST values also displayed significant r-values indicating the inadvertent sampling of closely related individuals. This highlights the close social groupings among cooperatively-breeding prairie vole that can exacerbate Lyme disease transmission. Thus, while elevated population connectivity aligns with prairie restoration goals, it also reinforces a need in adaptive management to evaluate environmental matrices for their permeability to vector-borne diseases.