VARIATION IN MITOCHONDRIAL-DNA AND THE BIOGEOGRAPHIC HISTORY OF WOODRATS (NEOTOMA) OF THE EASTERN UNITED-STATES

Genetic variation in 114 woodrats (Neotoma) from 33 locations in the eastern and central United States was examined using analysis of mitochondrial DNA (mtDNA) restriction sites, Results indicate that three major lineages of Neotoma floridana (southern, western, and northern) diverged in the early Pleistocene. The southern lineage exhibits substantial mtDNA variability and population structure. The pattern of mtDNA variation in the southern lineage suggests that vicariance events, including the insularization of Florida, have been important determinants of geographic variation. The low levels of sequence variation within the northern and western lineages indicate that woodrat populations in these areas are probably the result of relatively recent (Holocene) range expansions. These conclusions are not entirely consistent with the current taxonomy of eastern woodrats and suggest that taxonomic revision is warranted.