Systematics and Morphologic Variation in Two Chromosomal Forms of the Agile Kangaroo Rat (Dipodomys agius)

Morphologic variation between two chromosomal forms of Dipodomys agilis was analyzed by use of external, cranial, and bacular characters. Significant morphologic differences were evident between chromosomal forms. Discriminant-function analysis followed by examination of specimens from the Los Angeles Basin, California, suggested a broad zone of sympatry between the two chromosomal forms, primarily delineated by habitat and elevation. Animals with a diploid chromosomal number of 2n = 62 generally were collected in mesic woodland and coniferous forests at higher elevations in the San Gabriel, San Bernardino, and coastal Santa Monica mountains. Conversely, the southern chromosomal form (2n = 60) inhabits a mosaic of environments ranging from coastal grassland and chaparral in southern California to arid desert and conifer forests in Baja California. These two chromosomal forms appear to represent two distinct species.