GENETICS, ECOLOGY, AND CONSERVATION OF MONTANE POPULATIONS OF COLORADO CHIPMUNKS (TAMIAS-QUADRIVITTATUS)

Population genetics and ecological characteristics were assessed in re lictual montane populations of the Colorado chipmunk (Tamias quadrivit tatus). This study focused on conservation and systematic relationship s of two endangered populations of T. quadrivittatus inhabiting the Os cura and Organ mountains of central and southern New Mexico, relative to coniferous-forest populations found in northern latitudes. Results suggest that inbreeding has had a significant effect on genetic struct ure of populations of chipmunks, particularly in more arid regions of central and southern New Mexico. Levels of intrapopulation variability were a function of population size, as indicated by the significant a ssociation between area of forest habitat and average values of alleli sm, polymorphism, and heterozygosity. Patterns of allozymic differenti ation in the northernmost populations can be explained by dispersal, i n which populations connected by corridors of mesic woodland during th e Pleistocene or Recent received sufficient gene flow to account for t he generally low level of interpopulation genetic divergence. Converse ly, genetic divergence in central and more arid southern populations L ikely is a result of isolation and subsequent genetic drift associated with fragmentation of formerly continuous forest vegetation since the Pleistocene. Most relict-montane populations of T. quadrivittatus in New Mexico are small and patchy in distribution because of a close aff inity with specific ecological parameters. These genetically depaupera te populations are particularly susceptible to extinction owing to inc reasing human-induced destruction of habitat, as well as vagaries of s tochastic demographic and environmental phenomena. A goal of resource management in the southwestern United States must be to preserve relic t-mountaintop ecosystems that represent unique biogeographic links to the evolutionary history of the region. Within these mesic woodland an d forest patches, special effort must be made to preserve as much of t he species pool as possible, owing to increased habitat destruction an d fragmentation. Based on results of genetic, morphologic, and ecologi c data, a new subspecies of the Colorado chipmunk from the Oscura Moun tains, New Mexico, is described.