A genetic analysis of the Virginia opossum mating system: evidence of multiple paternity in a highly fragmented landscape.

Using molecular techniques, we examined patterns of paternity in Virginia opossums occupying a highly fragmented agricultural landscape in northern Indiana. During 2008, we collected tissue from 64 females and their pouch young in 34 forest patches distributed over a 1100-km(2) region. Using genotypes from 10 microsatellite loci, we determined the minimum number of fathers contributing to each litter using GERUD 1.0. Genotyped offspring with known mothers were then analyzed using CERVUS 3.0, incorporating genotypes from 317 males sampled from 2007-2008 to identify potential fathers. Our analyses revealed that promiscuity was common among females, with 26 (41%) litters having > or = 2 sires. Despite the fact that we intensively sampled forest patches for potential fathers, we only were able to identify 13 fathers contributing to 14 litters, with an average Euclidean distance of 18.7 km between father-offspring pairs found in disparate patches (N = 6). Our inability to identify most (85%) fathers of sampled litters, coupled with the extensive distances observed between putative father-offspring pairs, suggests that opossums may not maintain explicit home ranges in highly fragmented landscapes.