THE SYSTEMATICS AND BIOLOGY OF THE GENUS ZAPUS (MAMMALIA, RODENTIA, ZAPODIDAE) (CANADA, UNITED STATES).

摘要

This study was undertaken to determine specific and intraspecific relationships within the genus Zapus (Mammalia, Rodentia, Zapodidae). Subspecies are based on the biological subspecies concept where the subspecies is an evolutionary step between a population and species.;The ancestor of living Zapus was Zapus rinkeri-like. A population of this progenitor was apparently isolated by the glacier and meltwater Mississippi River in what is now southeastern United States; there it speciated into Zapus hudsonius. Other populations were isolated in the southwestern United States, the Sierra Nevada Mountains, and along the west coast from San Francisco to southwestern British Columbia. These peripheral populations, including Zapus hudsonius, closely resemble each other. As a result of environmental drying, perhaps during the Xerothermic Period (4000-6000 years B. P.), the western and southwestern peripheral populations were isolated. Coincidentally, an interior population speciated, apparently in the central Rocky Mountains; the resulting derived phenotype is that of Zapus princeps in the central portion of its range.;Zapus hudsonius and Z. princeps are sympatric in North Dakota and Minnesota, Colorado, and British Columbia. The two species can be discriminated by the nature of the paracone of the M1 and M2. In Z. hudsonius, it is not connected to the rest of the occlusal pattern; the first primary and first secondary folds are continuous medially. The paracone of Z. princeps, however, is broadly connected; the first primary and first secondary folds do not converge. The two species maintain their integrity in these areas. However, when the derived form (i.e., Z. p. princeps) contacts the southwestern and Pacific coast populations there is extensive intergradation.;The populations in northern New Mexico are a blend of the primitive (i.e., peripheral) and derived forms. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of school.) UMI.;Approximately 20,000 Recent specimens and representatives of fossil taxa were examined. Cranial and postcranial characteristics, colors, and when available bacula, sperms and karyotypes were incorporated into the morphological analyses. In addition, published biological data were summarized and analyzed for evidence of primary and secondary isolating mechanisms. Supplemental data were acquired during collection of 450 specimens in midwestern and western United States, western Canada, and Alaska.