Comparative morphology of the male reproductive tract in the rodent genus Peromyscus (Muridae)

"The male genital tracts of 28 species of Peromyscus were examined. On the basis of the accessory glands and other structures seven major groups can be distinguished within the genus. These correspond to the subgenera of Hooper and Musser (1964). The subgenus Haplomylomys possesses a full complement of accessory glands, including ampullary, vesicular, anterior prostate, dorsal prostate, ventral prostate, (two pairs), bulbo-urethral, and preputial glands. The subgenus Peromyscus differs only in lacking functional preputials, although these glands are present in rudimentary condition in some species. Megadontomys and Isthmomys are fundamentally similar to Peromyscus, although differing from that group and each other in numbers, proportional size, or morphology of certain glands. Isthmomys may diverge more from peromyscus than Megadontomys. The remaining three groups are markedly different from other species in genital morphology. Osgoodomys lacks vesicular and both anterior and dorsal prostate glands but has exceptionally large and distinctive ampullaries and well-developed preputials. Podomys and Habromys share the condition of greatly reduced vesiculars and anterior and dorsal prostates but differ in other features. Podomys has enlarged ampullaries and a deferent duct of unique structure, whereas Habromys has normal ampullaries and a typical derent duct but greatly enlarged ventral prostates. At least some of the species groups of the subgenus Peromyscus appear to be characterized by common genital features. These were more subtle than the difference betwen major groups and will require further study for verification. The genital data can be reconciled with the view that the genus Peromyscus is a natural assemblage of species in which some forms have diverged greatly, but they can be interpreted in support of the hypothesis that the genus is prophyletic. In either case, the present subgenera Osgoodomys, Podomys, and habromys may warrant exclusion from the genus on the basis of their extremely divergent reproductive morphology"--P. 45.