Molecular Phylogeography of Harvest Mice (Reithrodontomys megalotis) Based on Cytochrome b DNA Sequences

摘要

The species of harvest mouse Reithrodontomys megalotis belongs to one of the most diverse genera in North America with a wide latitudinal and altitudinal distribution. Previous studies suggest the existence of great morphological, chromosomal, and genetic variability; however, few of them have addressed the evolutionary patterns at the intraspecific level. We analyzed the evolutionary relationships and levels of genetic divergence in R. megalotis using DNA sequences of the mitochondrial cytochrome b gene. The results of the analysis with different phylogeographic methods show that R. megalotis represents a monophyletic group with respect to R. zacatecae, and populations included here split in three groups that were always consistent. Populations from the southern distribution form the first clade; from western North America form the second clade; and the third one comprises the populations of the Central Plains from the southern United States and the Mexican Plateau. The values of average genetic divergence within and among clades are low ( 3.4 %) compared to other species with similar distribution and times of divergence and origin. The results of this work are discussed in the context of the low genetic divergence found, given its wide and heterogeneous distribution together with its morphological variation. It is suggested that populations of R. megalotis have probably developed considerable phenotypic plasticity whose analysis and description should be approached from an ecological more than historical perspective.