ECOLOGICAL FACTORS IN SPECIATION OF PEROMYSCUS

Autor: W. Frank Blair
Rok vydání: 1950
Předmět:
Zdroj: Evolution. 4:253-275
ISSN: 0014-3820
Popis: Mice of the American genus Peromyscus are among the several kinds of animals that are particularly useful for study of the factors involved in speciation. This genus is widely distributed over North and Central America, and one or more of the fifty-five named species occurs in almost every part of these areas. Representatives of the genus occupy a wide variety of environments, and a wide range of ecological preferences is found even within a single, widely distributed species. This genus comprises sixteen or more species groups, or groups of species with close phylogenetic relationships. The species groups of Peromyscus, as arrailged on morphological resemblance by Osgood (1909) are important evolutionary categories. Members ofthe same species group, tested in the laboratory, are at least partially interfertile,, while members of different groups fail to cross (Dice, 1933a). The species groups of Peromyscus have been called cenospecies by Blair (1943a) following Turesson (1922) because of their apparent inability to interchange genetic materials. The species within the groups that have been studied show a wide range of difference in the degree of differentiation. The species within a group, in other words, represent varying stages in speciation, which permits reconstruction of the possible course of evolution of a new species. Other advantages of Peromyscus for evolutionary studies are numerous. Osgood's (1909) revision of the genus, based on more than 27,000 specimens, is outstanding among mammalian monographs that have used the methods of museum taxonomy. Most species of Peromyscus are readily adaptable to laboratory life, and consequently to breeding experiment. This fact was first recognized by Sumner (1932, summary), who pioneered in hybridization experiments and in the analysis of intraspecific geographic variation. It was exploited by Dice (numerous papers) principally in analyzing geographic variation in several wide-ranging species. An additional advantage of Peromyscus for evolutionary research results from the comparative ease with which the ecological relations of these mice may be determined. The ecological distribution and the habitat preferences of several species are fairly well known. Population densities and social behavior in natural populations of several species have been determined in recent years, following the lead of Burt (1940) and Blair (1940). Major disadvantages of Peromyscus for evolutionary studies are: (1) cytological investigations are not profitable because of the large number (forty-eight to fifty-two) and the small size of the chromosomes (see Cross, 1931), (2) the genetic bases of most wild phenotypes are difficult and laborious to analyze because of the presumably large number of genes with minor additive effects that are usually involved in coat color and in size of body parts. These difficulties, of course, are not limited to Peromyscus. My purpose here is to summarize what is presently known about geographic differentiation and speciation in Peromyscus and to indicate some major evolutionary problems to which work in this group may offer an eventual solution. Excluding museum studies, the history of Peromyscus as a medium for the study of evolutionary processes traces back some thirty-seven years to the beginning of Sumner's work. Most of the work with variation and speciation in this genus
Databáze: OpenAIRE
Externí odkaz: