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Systematic and ecological relations of Peromyscus oreas and P. maniculatas Sheppe, Walter Alvin

Abstract

Systematic analysis of 2500 Peromyscus specimens from Washington and British Columbia shows that P. oreas is largely reproductively isolated from P. maniculatus, and it is raised to specific status. These species maintain their identities over large areas in which they are sympatric. Some specimens may be hybrids, and a few samples may be from intergrade populations. P. m. austerus and P. m. artemisiae produced fertile hybrids in the laboratory, but P. oreas failed to breed. Field studies revealed that oreas and maniculatus are in part ecologically isolated in areas where both occur. Both species have more restricted habitat distribution in the presence of the other, and interspecific competition is suggested as a cause. Greatest reproductive activity was in spring and early summer; there was no breeding in late summer. Oreas ceased to breed earlier than maniculatus. In June adults outnumbered young of the year in the catch, but by July this was reversed. Young males were caught more often than young females, but adult females were caught more often than adult males, suggesting that females live longer than males. Oreas probably developed partial reproductive isolation when separated from other Peromyscus stocks by Pleistocene glaciation. It has remained distinct from maniculatus through a combination of geographical, ecological, temporal, psychological, and genetic isolation.

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