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Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila Mexico   By: (1916-2007)

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~University of Kansas Publications~ ~Museum of Natural History~

Volume 7, No. 12, pp. 591 608

March 15, 1955

Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México

BY ROBERT J. RUSSELL AND ROLLIN H. BAKER

~University of Kansas~ ~Lawrence~ 1955

~University of Kansas Publications, Museum of Natural History~

Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Robert W. Wilson

Volume 7, No. 12, pp. 591 608 Published March 15, 1955

~University of Kansas~ ~Lawrence, Kansas~

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1955

25 5679

Geographic Variation in the Pocket Gopher, Cratogeomys castanops, in Coahuila, México

By

Robert J. Russell and Rollin H. Baker

The plateau pocket gopher, Cratogeomys castanops , inhabits open lands from southeastern Colorado southward onto the Mexican Plateau as far south as southern San Luis Potosí and southeastern Zacatecas and southeastward to the Coastal Plain of northern Tamaulipas. This species occurs at elevations from as low as 26 feet at Matamoras in Tamaulipas to as high as 8700 feet in valleys of south eastern Coahuila. In 1934, Nelson and Goldman (Proc. Biol. Soc. Washington, 47:135 154, June 13, 1934) revised the genus Cratogeomys and decided that six subspecies of C. castanops occurred in Coahuila. In the present account, we describe four previously unknown subspecies from Coahuila, exclude from the state two others recorded from there by Nelson and Goldman, and show that three others named previously from adjacent Mexican states do occur in Coahuila. This makes eleven subspecies now known from that state. From Coahuila Nelson and Goldman had 35 study specimens of C. castanops from seven localities and we have had 234 specimens from 63 localities. Consequently we have been able to define with greater certainty, than formerly was possible, the geographic distribution of C. castanops in this Mexican state and similarly analyze more completely the geographic variation.

Coahuila is near the center of the geographic range of C. castanops . The occurrence of 11 subspecies within the state seems to be the result of partial or perhaps, in some cases, total isolation of populations of C. castanops because of the highly dissected topography and the variability of the soil. Cratogeomys castanops is a sedentary animal preferring open plains mantled by suitable soils, preferably sandy in texture, in which the animals can dig their elaborate underground systems of runways. Thin soils of hard texture and rocky soils do not offer optimum habitat for C. castanops , and the animals usually are absent or uncommon in such situations. Desert mountains with their thin rocky soils, elevated passes, perpendicular rocky cliffs, and stands of oaks and conifers at higher elevations present impassable barriers for pocket gophers of this species. The Río Grande, bordering Coahuila to the north, in many places flowing through steep walled cañons, also seems to be a barrier that this fossorial rodent does not cross; distinct subspecies occur on the two sides of the river directly opposite each other (also see Nelson and Goldman, op. cit. : 143). Smaller streams, such as the Río Salado, Río Nazas and Río Salinas, seem to be unimportant barriers to the passage of these pocket gophers. The food supply of C. castanops seems adequate in most situations and consequently food is unimportant in governing the distribution of this species. Principal foods of C. castanops are fleshy tuberous roots of well distributed desert shrubs, but in the valleys of the high mountains of southeastern Coahuila, where desert shrubs are absent, roots and leaves of low growing forbs are eaten... Continue reading book >>




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