Genetic Compatibility of Peromyscus maniculatus and Peromyscus melanotis, as Indicated by Breeding Studies and Morphometrics

Abstract

Reproductive compatibility, skull morphometrics, color of pelage, and size and structure of bacula and sperm were compared in nine populations of Peromyscus maniculatus and P. melanotis from the southwestern United States and Mexico. Breeding data indicated that there is no conspicuous reduction of fertility between populations of P. maniculatus , or of P. melanotis. However, no P. maniculatus × P. melanotis hybrids were produced. In most instances, patterns of morphometric variation corroborated genetic affinities revealed by breeding, chromosomal, and electrophoretic studies; however, it is unlikely that the same conclusions would have been drawn without the supporting breeding, chromosomal, and electrophoretic data—it is possible that the two species would have been considered conspecific if only morphometric data were used. Pelage color, and size and structure of bacula and sperm proved of little value in separating P. melanotis and P. maniculatus . Based on cranial morphology, certain individuals of P. maniculatus rufinus from Otero County, New Mexico, and P. melanotis from near El Salto, Durango, are difficult to distinguish to species. This similarity in morphology is probably due to convergent evolution resulting from adaptations to similar habitats. That P. maniculatus and P. melanotis are sibling species is substantiated by the fact that certain populations of the latter from southern Arizona previously were referred to as P. maniculatus rufinus. Breeding, electrophoretic, and chromosomal data clearly reveal that these populations are P. melanotis; however, when these populations are compared with others of P. melanotis , no basis for subspecies distinction can be found. Therefore, P. melanotis remains a monotypic species.