| The San Joaquin pocket mouse (Perognathus inornatus) is a California endemic currently comprising three subspecies (inornatus, neglectus and psammophilus). From 1991-2015, we investigated the cytogenetic and morphometric characteristics and habitat associations of P. inornatus at 63 locales throughout the western Mojave Desert. Karyotypes were prepared by Dr. James L. Patton (emeritus curator, MVZ Berkeley, CA) and all were characterized by a diploid complement of chromosomes (2n = 52) not previously described. Principal components analysis indicated that the 52-chromosome form was closely associated with P. i. neglectus (2n=56) but strongly divergent from P. i. inornatus (2n=50) and P. longimembris (2n=56). P. inornatus was significantly larger in total length, head-body length, hind foot length and weight than P. longimembris. It was found primarily on well-drained, coarse soils in Creosote Bush Scrub, Saltbush Scrub, Joshua Tree Woodland, Rabbitbrush Scrub and Juniper Woodland at elevations between 2,600-3,600 feet. The taxonomy of P. inornatus is unresolved, and it is the only species in the genus that includes more than one diploid number. It is important to view the 52-chromosome form independently for conservation purposes, since it occupies a small geographic area subjected to increasing habitat loss from renewable energy development and other human-related activities. |