Systematic Implications of Karyotypic and Morphologic Variation in Mainland Peromyscus from the Pacific Northwest

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Abstract
Karyotypic data from a total of 129 deer mice from Washington and coastal British Columbia indicated the presence of two distinct karyotypic groups, a “low FN” group (FN = 74–76) corresponding to P. maniculatus austerus, and a “high FN” group (FN = 85–88) corresponding to P. oreas. The absence of karyotypic intermediates at localities of sympatry is interpreted as verifying the specific status of P. oreas. Banding data indicated the presence of more extensive chromosomal variation within each of these forms than divergence between them. Analyses of standard external measurements were consistent with the karyotypic data and revealed significant differences in total length, length of tail and length of hind foot between these species. Due to overlap in the ranges of these measurements, however, some specimens could not be identified positively to species without karyotypic data. Comparison of the banded karyotype of P. oreas to data available from other P. maniculatus group species suggests that P. oreas and P. sitkensis shared a common ancestor since their divergence from the maniculatus stock.