THE EVOLUTIONARY DYNAMICS OF THE DESERT WOODRAT, NEOTOMA LEPIDA.

Abstract

Neotomla lepida shows a great amount of intraspecific phenotypic variation. Hall and Kelson (1959) list 30 subspecies. There is, furthermore, a great deal of variation within each subspecies, and in particular the subspecies investigated here, N. lepida lepida. As these animals construct permanent dwellings, some of which may have been inhabited intermittently for thousands of years (XVells and Berger, 1967), it is assumed that under most circumstances the distance they wander is limited, causing the fine-scaled structure of partial isolation, without marked environmental differences which Wright (1951) mentions. The woodrats used in this study were collected at Pisgah and Nemo Lava Flows in Lavic Valley, California, in ecotonal areas of black lava and white sand. The distribution and selection of coat color phenotypes due to geographical and historical events as well as stochastic processes and immigration is the subject of this paper. Another function of this paper is to present a new combination of techniques for use in the analysis and interpretation of coat color characteristics. Formerly analyses of mammalian coat color characteristics have been performed with respect to both the genetic peculiarities of coat color (Searle, 1968) and the distribution of coat color phenotypes (Benson, 1933; Blair, 1947; Stodart, 1965); however, quantitative measurements of coat color have been lacking. The perfection of continuously scanning spectrophotometers capable of measuring coat reflectance has made possible the detailed analysis here of the microgeographic distribution of small mammals in terms of coat pigment.