Population Genetics of Kangaroo Mice, Microdipodops (Rodentia: Heteromyidae)

Dark (Microdipodops megacephalus) and pallid (Microdipodops pallidus) kangaroo mice are ecological specialists found in arid regions of the Great Basin Desert of the southwestern United States. Historical and current habitat alterations have resulted in disjunct distributions and severely diminished abundance of both species. Phylogenetic and phylogeographic research has discovered unique mitochondrial clades within M. megacephalus (eastern, central, western, and Idaho clades) and M. pallidus (eastern and western clades). Population-genetic analyses targeting the same mitochondrial markers also have found low amounts of maternal gene flow among the clades. However, little is known about population structure and genetic demography (historical and current migration rates, historical and current effective population sizes) within each mitochondrial clade.

Herein, nuclear-encoded microsatellite loci were isolated to evaluate the underlying processes that may have molded kangaroo mouse relationships and distributions. Results from population-genetic analyses support previous findings that there are at least three genetically distinct clades within M. megacephalus and two such clades within M. pallidus. Three clades of M. megacephalus appear to have undergone different demographic histories, with little to no migration among clades. The two clades of M. pallidus also appear to have experienced varying demographic change although there has been small but recent migration between them. Additionally, the contemporary effective population sizes of all clades within Microdipodops appear to be low, suggesting that these populations may have difficulty coping with environmental pressures and hence are at risk of extinction. Results of this study are consistent with the recommendation that each Microdipodops clade should be managed as separate units and continually monitored in an effort to conserve these highly specialized taxa.