Systematic Status of the Mojave Ground Squirrel, Spermophilus mohavensis (Subgenus Xerospermophilus)

The systematic status of the sibling species Spermophilus mohavensis and S. tereticaudus (subgenus Xerospermophilus) is investigated throughout their range, based on allozymic and chromosomal data. The species have different diploid numbers (2N = 36 in S. tereticaudus, 2N = 38 in S. mohavensis) and exhibit a moderate level of genie similarity (S = 0.78). Hybridization of the species was detected only at a single site, whereas allelic introgression appears to be confined to an estimated 60 km reach of the Mojave River wash. Pending more detailed analysis of this single site, we recommend that the two taxa retain their current status as full biological species.