PARENT SESSION

Genetics/Evolution 1 -- Session Chair: Hopi Hoekstra-- University Center, Kate Buchanan Room

PHYLOGEOGRAPHY AND SYSTEMATICS OF KANGAROO MICE, MICRODIPODOPS MEGACEPHALUS, FROM THE MONO BASIN. John C. Hafner¹, Emily Reddington¹, Matthew T. Craig² and Jens PC. Franck³. ¹ Moore Laboratory of Zoology and Department of Biology, Occidental College, Los Angeles, California; ² Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California; ³ Department of Biology, Occidental College, Los Angeles, California.

ABSTRACT- Kangaroo mice from the Mono Basin and adjoining valley regions of California and Nevada have been recognized previously as two subspecies: Microdipodops megacephalus nasutus, and Microdipodops megacephalus polionotus. The populations of M. megacephalus inhabiting the Mono Basin region represent a western distributional isolate that is separated from the principle eastern and western distributional units of the species by at least 100 kilometers of unsuitable habitat. This study examines the genetic variation, systematic status, and phylogeography of the kangaroo mice from the Mono Basin region using molecular phylogenetic techniques. We analyzed sequence data from two mitochondrial genes, 16s rDNA (550 bp) and cytochrome b (468bp); these data sets were examined individually and as a combined data set (1018bp). Examination of the combined data set shows a 1.31% uncorrected sequence divergence between the kangaroo mice from the Mono Basin area and those from the eastern distributional unit; the eastern and western distributions of M. megacephalus differ by 5.39% and the two species of kangaroo mice are separated by 8.62%. Maximum parsimony, neighbor-joining, maximum likelihood, and Bayesian inference result in trees with a consistent and strongly supported topology. In each of the trees, the eastern and western distributional subunits of M. megacephalus form monophyletic clades, the Mono Basin kangaroo mice are nested within the eastern clade, and Microdipodops pallidus forms a distinct clade (outgroup is Dipodomys microps). As there is very little genetic divergence within the kangaroo mice from the Mono Basin Region, we find no molecular support for the recognition of two separate subspecies. This lack of differentiation between the two subspecies is supported by previous morphologic, karyotypic, and allozymic studies. We therefore recommend that only one subspecies of kangaroo mice, M. m. polionotus, be recognized from the Mono Basin region.

KEY WORDS: Microdipodops megacephalus, Mono Basin , kangaroo mice, molecular phylogenetics