Microgeographic Lineage Analysis by Mitochondrial Genotype: Variation in the Cotton Rat (Sigmodon hispidus)

We evaluate the use of mitochondrial DNA (mtDNA) genetic markers to describe population structure and matrilineal kinship on a microgeographic scale. An analysis of restriction site variation in 134 cotton rats (Sigmodon hispidus) collected from a 3.2 hectare field revealed significant spatial and temporal heterogeneity in frequencies of mtDNA genotypes among nest sites. Inspection of particular genotypes provided additional information about minimum numbers of female lineages (family units) per nest site, and the possible matrilineal affiliations of individuals. However, since shared genotypes are not necessarily synapomorphs having arisen within the study area, conclusions about dispersal must remain reserved. Study of the maternally-transmitted mtDNA genome offers novel perspectives on the meaning of microgeographic population structure.