Conspecificity of Two Pocket Mice, Perognathus Goldmani and P. Artus

Part 1

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UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 9, No. 18, pp. 513-518, 1 map January 14, 1960

Conspecificity of two pocket mice, Perognathus goldmani and P. artus

E. RAYMOND HALL AND MARILYN BAILEY OGILVIE

UNIVERSITY OF KANSAS LAWRENCE 1960

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch, Robert W. Wilson

Volume 9, No. 18, pp. 513-518, 1 map Published January 14, 1960

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED IN THE STATE PRINTING PLANT TOPEKA, KANSAS 1960

28-1243

Conspecificity of two pocket mice, Perognathus goldmani and P. artus

E. RAYMOND HALL AND MARILYN BAILEY OGILVIE

Perognathus goldmani Osgood and Perognathus artus Osgood from southern Sonora, northern Sinaloa and adjoining parts of Chihuahua and Durango, are two named kinds of the Perognathus intermedius group of pocket mice, of the subgenus Chaetodipus. Until now the two kinds have been treated in the literature as two species. In both goldmani and artus the upper parts are Ochraceous-Buff (capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) having a strong admixture of black. The lateral line is Ochraceous-Buff, and the underparts are white. P. goldmani is larger than P. artus (see measurements beyond) and has more inflated tympanic bullae and a relatively narrower (transverse to long axis of skull) interparietal bone.

Specimens from a transect of southeastern Sonora show intergradation between Perognathus goldmani and P. artus. From northwest to southeast the specimens are as follows: one mile east of Buena Vista, on Río Yaqui Reservoir, 1000 feet (2 specimens, K. U.); Alamos, 1200 feet (7, U. S. B. S.); four and a half miles southeast of Alamos, 1000 feet (5, K. U.); nine miles southeast Alamos, 1000 feet (5, K. U.). The specimens (P. goldmani) from Río Yaqui Reservoir are largest. Those from nine miles southeast of Alamos (P. artus) are smallest. Those from Alamos proper are P. goldmani. Those from four and a half miles southeast of Alamos (80051-80055 K. U. collected by Robert L. Packard and here referred to goldmani) include two as large as goldmani from Alamos, one as small as artus from nine miles southeast of Alamos, and two that are intermediate in size. Features other than size, considered geographically, also suggest intergradation.

Six specimens (61409-61413, 61415 K. U. collected by J. R. Alcorn), including five adults (permanent fourth premolar of full height and having cusps worn but not so much as to make a lake of dentine), from four miles north of Terrero, Sinaloa, also seem to be intergrades between Perognathus goldmani and Perognathus artus. As compared with adults of P. goldmani from 10 miles north-northwest of Los Mochis, Sinaloa, and P. artus from one mile south of Pericos, Sinaloa, the specimens from four miles north of Terrero are almost exactly intermediate in length of hind foot, width of interparietal, and width of tympanic bullae. Intermediacy is shown also in total length of animal (slightly nearer that of artus) and length of tympanic bullae (slightly nearer that of goldmani). In lack of inflation laterally of the mastoidal bullae the specimens agree with artus. In occipitonasal length and mastoidal breadth the specimens from four miles north of Terrero average even larger than goldmani from 10 miles north-northwest of Los Mochis but not so large as specimens of goldmani from the type locality, which is still farther north. The uninflated mastoidal bullae "tip the balance" slightly in favor of artus to which the specimens from four miles north of Terrero are here referred. The degree of inflation of the mastoidal bullae elsewhere varies geographically. For example, the mastoidal bullae of the 25 specimens of goldmani from two and a half miles north of El Fuerte, Sinaloa, are intermediate in size as between those of goldmani and artus.

The morphological intermediacy of the specimens from four and a half miles southeast of Alamos and of those from four miles north of Terrero, along with the geographic intermediacy of the two localities where the specimens were obtained constitute basis for arranging artus as a subspecies of goldmani that has one page of priority.

1. P. g. artus

2. P. g. goldmani]

~Perognathus goldmani goldmani~ Osgood

Perognathus goldmani Osgood, N. Amer. Fauna, 18:54, September 20, 1900, type from Sinaloa, Sinaloa.

Range.--See map 1.

Measurements.--Average of five topotypes (Osgood, op. cit.:55): total length, 202; tail vertebrae, 112; hind foot, 28; occipitonasal length, 27.7; mastoidal breadth, 14.5; greatest width of interparietal, 7.4.

Records of occurrence (in each state the localities are listed from north to south).--Sinaloa: 2-1/2 mi. N El Fuerte, 25 K. U.; Sinaloa (Osgood, N. Amer. Fauna, 18:55, September 20, 1900); 10 mi. NNW Los Mochis, 18 K. U. Sonora: 1 mi. E Buena Vista, on Río Yaqui Reservoir, 1000 ft., 2 K. U.; Camoa, 7 (U. S. N. M.); Tesia (Burt, Miscl. Publ. Mus. Zool., Univ. Michigan, 39:46, February 15, 1938); Alamos, 7 (U. S. N. M.); 4-1/2 mi. SE Alamos, 1000 ft., 5 K. U.; Chinobampo (Burt, loc. cit.); 3 mi. NNW Bacarachi [= Bacavachi], 2 K. U.

~Perognathus goldmani artus~ Osgood

Perognathus artus Osgood, N. Amer. Fauna, 18:55, September 20, 1900, type from Batopilas, Chihuahua.

Range.--See map 1.

Part 2

Measurements.--Average of five adult topotypes (Osgood, op. cit.:55, 63): total length, 191; tail vertebrae, 106; hind foot, 24.6; occipitonasal length, 25.4; mastoidal breadth, 12.4; greatest width of interparietal, 7.1.

Remarks.--Considerable individual variation has been noted in each of several populations of Perognathus goldmani artus. For example, in 14 adults from Culiacán, Sinaloa, the variation is 25.0 to 27.9 in occipitonasal length and in mastoidal breadth is 12.6 to 14.0. Ten specimens (83122-83131 Univ. Mich.) labeled as from Carimechi, Río Mayo, Chi[huahua], were recorded by Burt and Hooper (Occas. Papers Mus. Zool., Univ. Michigan, 430:6, May 27, 1941) as from "near Carimechi." They identified the two largest (83130 and 83131) as Perognathus goldmani and the others as Perognathus artus. These identifications were reasonable in the light of knowledge available in 1941, but in the light of information presently available from the now more abundant material it is clear that all 10 of the specimens are P. g. artus. Examination (by Hall) of the specimens reveals that the differences relied upon by Burt and Hooper to differentiate the two species are well within the range of individual variation. For example, the variation (5.3 to 5.6 mm.) in width of the supraoccipital is less than in each of some other series of specimens of equal age of P. g. artus from other localities.

Also, there is geographic variation in the mice here assigned to the subspecies P. g. artus; skulls are smaller in the northern part of the geographic range and become gradually larger toward the south. In five adults from the northern part (Batopilas 3, and 26 mi. NE Choix 2) the mean of 12.6 of the mastoidal breadth of the skull is significantly smaller than the corresponding mean of 13.3 in 21 adults from the southern part (32 mi. SSE Culiacán 14, and El Dorado 7). The pelage of individuals from one and a half miles southwest of Tocuina is notably dark both above and below; the venter is dusky rather than white. We suppose that the darker color is a response to a dark-colored substrate--lava and soils derived from dark lava.

Records of occurrence (in each state the localities are listed from north to south).--Chihuahua: Carimechi, Río Mayo, 10 U. Mich.; 1-1/2 mi. SW Tocuina [Tocuina is a construction camp, in 1959, on NW bank of the Río Septentrión, and is not the Tacuina shown on some maps SE of that River], 10 K. U.; Batopilas, 6 U. S. N. M. Durango: Chacala (Osgood, N. Amer. Fauna, 18:55, September 20, 1900). Sinaloa: Rancho Rosalita, 26 mi. NE Choix, 3 K. U.; 4 mi. NE Terrero, 6 K. U.; 1 mi. S Pericos, 20 K. U.; 12 mi. N Culiacán, 29 K. U.; 32 mi. SSE Culiacán, 20 K. U.; 6 mi. N, 1/2 mi. E El Dorado, 41 K. U.; El Dorado, 2 K. U. Sonora: Río "Cuchahaque," 11.3 mi. E Alamos, 5 Univ. Arizona; 9 mi. SE Alamos, 1000 ft., 5 K. U.

We have not seen any specimens that are intergrades between P. goldmani and Perognathus intermedius (subspecies intermedius or lithophilus), nor between P. goldmani and Perognathus nelsoni (subspecies nelsoni or canescens), nor between P. intermedius and P. nelsoni. Collecting and studying specimens from geographically appropriate places to test for intergradation between these three species would be worthwhile as a means of improving our knowledge of the taxonomy of these mice.

We are obliged to J. R. Alcorn and William L. Cutter for collecting many of the specimens used by us, to the Watkins Fund of the Kansas University Endowment Association and to the American Heart Fund for financial assistance with collecting the specimens, to the National Science Foundation for financial assistance with study of the specimens in the Museum, to William H. Burt of the University of Michigan, and to Stanley P. Young, Richard P. Manville and Viola S. Schantz of the Biological Surveys Collection of the United States Fish and Wildlife Service for lending certain specimens.

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