EVOLUTIONARY RELATIONSHIPS OF POCKET GOPHERS (CRATOGEOMYS CASTANOPS SPECIES GROUP) OF THE MEXICAN ALTIPLANO.

The Southern Coahuila Filter-Barrier (SCFB) effectively subdivides the mammalian fauna of the Mesa del Norte, the northern and most extensive section of the Mexican Altiplano. Pocket gophers of the genus Cratogeomys north and south of this filter-barrier have been informally recognized as 2 distinct species, C. castanops and C. goldmani, respectively. Support for species recognition derives from early morphological comparisons and recent chromosomal and ectoparasite studies. Contradictory conclusions based on the only comprehensive morphometric study have prevented formal recognition of C. goldmani. A morphometric reevaluation based on ratiotransformed data reveals that the previous analysis was unduly biased by size, an ecophenotypically plastic character. When this factor is removed, morphometric variation is fully concordant with chromosomal diploid number and sequence data of mitochondrial and nuclear DNA. We provide synonymies and descriptions for C. goldmani apart from C. castanops, and revise the number of subspecies from a total of 26 to 2 subspecies in each species. The SCFB is most effective in its central portion (Desierto Mayán), and least effective in its western portion (Río Nazas), which should be geographically broadened to include the neighboring Río Aguanaval. [ABSTRACT FROM AUTHOR]