Chromosomal variation and differentiation among insular populations of Peromyscus from the Pacific Northwest

Abstract

Karyotypic data from 561 deer mice (Peromyscus spp.) from populations on islands off British Columbia and Washington indicate the presence of two distinct karyotypic groups, a low fundamental number (FN) group (FN = 74–78) and a high FN group (FN = 85–92). The absence of karyotypic intermediates at nine localities of sympatry is interpreted as demonstrating that the two FN groups represent distinct species. Based on data from comparable mainland forms, the low FN form is considered to represent Peromyscus maniculatus and the high FN form is suggested to be conspecific with Peromyscus areas. Chromosomal banding data indicate extensive chromosomal variation within each of these species and provide discrete karyotypic characters unique to each species. The inclusion of the high FN insular forms with P. oreas does not affect the chromosomally determined cladistic placement of P. oreas as a laxon derived from P. maniculatus.

Cytogenetic nomenclature of deer mice, <i>Peromyscus </i>(Rodentia): revision and review of the standardized karyotype

“…A peri centric-inversion polymorphism of Chr 14 occurs in some pop ulations of P. maniculatus (Gunn, 1988).…”

“…6, and 7 in northwestern populations of spe cies in the maniculatus species group (Pengilly et al, 1983;Gunn and Greenbaum. 1986;Hale, 1986;Gunn. 1988).…”

Morphological variation and taxonomy of chromosomally differentiated Peromyscus from the Pacific Northwest

“…The geographic region of the Pacific Northwest, including northern Washington and southern coastal British Columbia, encompasses 13 insular subspecies of P. maraiculams (Cowan and Suiguet 1965;Hall 198 1). Based on patterns of variation in the number of arms in the autosomal complement (fundamental number, FN), recent studies have suggested the need for systematic revision of Peromyscus manicuIatus from the Pacific Northwest (Thomas 1973;Sunn and Greenbaum 1986;Gunn 1988). Nondifferentially stained and banded chromosomal dab and the analysis of standard external measurements of deer mice from mainland Washington and coastal British Columbia (Gunn and Greenbaum 1986) deinonstrated discrete karyotypic and morphologic differences between P. oreas (FN = 85 -88) and the partially sympatric P. rn.…”

“…A karyotypic study of Peromyscus from Vancouver Island and associated islands in the waterways specific rearrangements that closely parallels that of mainland P. oreas and P. m. austerus (Gunn and Greenbaum 1986). Based on these data, Gunn (1988) suggested that for the insular deer mice, only the low FN (FN = 74-78) forms represent P. maniculatus and that the high FN (FN = 85-92) forms are conspecific with P. oreas of the adjacent mainland. One other northwestern form of Peromyscus, P. sitkensis, is known to have karyotypes (Bengilly et al 1983) indistinguishable from those of P. oreas (Sunn and Greenbaum 1986;Gunn 1988).…”

Brief communication. Systematic implications of chromosomal data from two insular species of Peromyscus from the Gulf of California

“…Recent analyses, however, have raised questions concerning the circumscriptions of some of the inclusive species and stimulated reconsiderations of the systematic affinities and composition of this group. Analyses of genetic and morphologic characters resulted in the recognition of P. keeni, subsuming P. sitkensis and including most of the subspecies of P. maniculatus from the Pacific northwest (Allard et al 1987;Allard and Greenbaum 1988;Calhoun and Greenbaum 1991;Gunn 1988;Gunn and Greenbaum 1986;Hogan et al 1993;Sullivan et al 1990). Chromosomal data have also pro- vided support for specific differentiation of the historically recognized grassland (short-tailed) and forest ( long-tailed) ecophenotypes in the northeastern range of P. maniculatus (Myers Unice et al 1998).…”