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12 OCCASIONAL PAPERS MUSEUM TEXAS TECH UNIVERSITY Veracruz, oaxacensis the highlands in Oaxaca and Chiapas where the Sierra Madre Oriental and Sierra Madre del Sur meet, evides the Sierra Madre del Sur region of Oaxaca and Guerrero, and hylocetes the Cordillera Transvolcanica zone of Jalisco. If one assumes a southern origin for this species (see Carleton, 1977 and 1979, for further discussion) and an oaxacensis-like ancestor (the most wide-ranging taxon), then dispersal northward along the Sierra Madre Oriental could have given rise to the aztecus type, and dispersal to the west along the Sierra Madre del Sur and Cordillera Transvolcanica ranges could have produced evides and hylocetes. Alternatively, if one assumes that El aztecus forms the ancestral stock for the remaining three subspecies, then theaztecus- oaxacensis-evides-hylocetes relationship would result from a clockwise radiation into these mountain ranges of central and southern MCxico. Obviously, a cladistic analysis of G-band chromosomes is needed to determine which taxon possesses the primitive karyotype necessary for testing the origin of these subspecies. As a result of a lack of congruence among data sets, it is difficult to resolve the taxonomic relationships of the four subspecies ofll aztecus. First, the qualitative and quantitative data are incom- patible, although the qualitative data herein support the phylogenetic study of Bradley and Schmidly (1987). The qualitative data (this study; Bradley and Schmidly, 1987) show a close relationship of aztecus to oaxacensis and evides to hylocetes. The quantitative data, on the other hand, depict aztecus as being distinct from the other three subspecies. The incongruence of the qualitative and quantitative data sets herein is suggestive of that found in a similar study of phallic characters in El boylli, Lq beatae, and 19 levipes (Bradley et al., 1989). Second, neither data set is congruent with Carleton's (1979) hypothesis of elevation zones being correlated with morphological variation. Third, the phallic data set is not concordant with the chromosomal variation reported by Smith et al. (1989). The difficulty in resolving the taxonomy of I? aztecus is similar to the situation that has existed in El boylii, 19 beatae, and El levipes (Houseal et al., 1987; Rennert and Kilpatrick, 1986, 1987; Schmidly et al., 1988; Bradley and Schmidly, 1987; Bradley el al., 1989). Complete and independent data sets will be needed for further taxonomic resolution of this group.
BRADLEY ET AL.-GLANS PENES AND BACULA OF PEROMYSCUS 13 We thankT. W. Housed, S. A. Smith, K. M. Davis, J. Ensink, M. W. Allard, D. Werbitsky, P. D. Rennert, C. W. Kilpatrick, I. F. Greenbaum, and D. W. Hale for their assistance in obtaining specimens. We also are indebted to A. C. Carmichael, The Museum, Michigan State University, and P. Myers and L. R. Heaney, University of Michigan Museum of Zoology, for allowing us to borrow specimens. Special thanks to H. Sittertz-Bhatkar for preparing the scanning electron microscope photomicrographs, and to the Texas Agriculture Experiment Station for supporting that aspect of the research. We also thank J. N. Derr, K. L. Bowers, and L. C. Bradley for comments and assistance during various stages of this manuscript. The research was supported by the National Science Foundation through grants DEB 81-17447 (I. F. Greenbaum and D. J. Schmidly) and DEB 81-18966 (C. W. Kilpatrick). We thank the Direcci6n General de Flora y Fauna Silvestres for granting permission to collect in MCxico, and the numerous faculty and students at Universidad Nacional Aut6noma de MCxico who aided our work in Mexico. This paper represents contribution number TA-25156 of the Texas Agricultural Experiment Station. BRADLEY, R. D., AND D. J. SCHMIDLY. 1987. The glans penes and bacula in Latin American taxa of the Pmmyscus bqlii species group. J. Mamm., 68:595-616. BRADLEY, R. D., D. J. SCHMIDLY, AND R. D. OWEN. 1989. Variation in the glans penes and bacula among Latin American populations of the Peromyscus bylii species complex. J . Mamm., 70:712-725. CARLETON, M. D. 1977. Interrelationships of populations of the Peromyscus boylii species group (Rodentia: Muridae) in western Mexico. Occas. Papers Mus. Zool., Univ. Michigan, 675: 1-47. . 1979. Taxonomic status and relationships of Peromycus bqlii from El Salvador. J. Mamm., 60:280-296. HAMILTON, W. J., JR. 1946. A study of the baculum in some North American Microtinae. J. Mamm., 27:378-387. HOOPER, E. T. 1958. The male phallus in mice of the genus Pmmyscus. Misc. Publ. Mus. Zool., Univ. Michigan, 105: 1-24. . 1968. Classification. Pp. 27-74, in Biology of Pmmyscus (Rodentia) (J. A. King, ed.), Spec. Publ., Amer. Soc. Mamm., 2:l-593. HOUSEAL, T. W., I. F. GREENBAUM, D. J. SCHMIDLY. S. A. SMITH. AND K. M. DAVIS. 1987. Karyotypic variation in Peromyscus bqlii from Mexico. J. Mamm., 68:281-296. LEE, M. R., AND E F. B. ELDER. 1977. Karyotypes of eight species of Mexican rodents (Muridae). J. Mamm., 58:479-487. LIDICKER, W. Z., JR. 1960. The baculum of Dipodomys ornatus and its implication for superspecific groupings of kangaroo rats. J. Mamm., 41 :495-499. RENNERT, P. D., AND C. W. KILPATRICK. 1986. Biochemical systematics of populations of Peromyscus bvlii. I. Populations from east-central Mexico with low fundamental numbers. J. Mamm., 67:481-488. . 1987. Biochemical systematics of populations of P'myscus boylii. 11. Chromosomally variable populations from eastern and southern Mexico. J. Mamm., 68:799-811.