PROC. BIOL. SOC. WASH. 105(4), 1992, pp. 841-866 SYSTEMATICS AND BIOGEOGRAPHY OF THE NEW ENGLAND COTTONTAIL, SYLVILAGUS TRANSITIONALIS (BANGS, 1895), WITH THE DESCRIPTION OF A NEW SPECIES FROM THE APPALACHIAN MOUNTAINS Joseph A. Chapman, Kenneth L. Cramer, Nico J. Dippenaar, and Terence J. Robinson Abstract. —Multivariate statistical analyses of 19 cranial and toothrow mea-surements of 274 adult cottontails, hitherto referred to as Sylvilagus transi-tionalis, were undertaken. Our results provide clear evidence of two mor-phometrically distinct taxa within what has conventionally been regarded as a single species, S. transitionalis, and thus support previous investigations which had revealed two discrete karyotypes (2N = 46; 2N = 52). We consider the congruence in data sets to support the recognition of two sibling species in S. transitionalis. As here defined, the New England cottontail, S. transitionalis (2N = 52), is restricted to boreal habitat in Maine, New Hampshire, Vermont, Massachusetts, Connecticut, Rhode Island and New York as far west as the Hudson River. The new Appalachian cottontail species, Sylvilagus obscurus, is generally an inhabitant of higher elevations and is restricted to the Appa-lachian Mountains and their associated mountain balds from the Hudson River through New York, Pennsylvania, Maryland, West Virginia, Virginia, Ten-nessee, North Carolina, South Carolina, Georgia and Alabama. The two species are phenotypically very similar but subtle differences in cranial shape, partic-ularly in the anterior and medial portions of the skull, allow for their delineation. Diagnostic cranial ratios, indicated by multivariate procedures, in conjunction with the results from discriminant function analysis, provide a reliable and practical means of species identification in the absence of chromosomal data. In addition we speculate on the possible biogeographic processes in the New York area that may have contributed to the evolutionary divergence of these taxa during the Wisconsinan glaciation. As currently understood, the New En-gland cottontail, Sylvilagus transitionalis, is primarily an inhabitant of dense woodland and boreal environments (Chapman & Pa-radiso 1972, Chapman 1975, Chapman et al. 1982, Chapman & Ceballos 1990). The species is reported to range from south-eastern New England south, along the Ap-palachians, to Alabama (Hall 1981, Chap-man & Stauffer 198 1). Within this region it has a mosaic distribution that is thought to reflect, in part, gradual climatic change since the last glaciation and the concomitant re-invasion of lowland areas by the more ubiq-uitous eastern cottontail, S. floridanus. These factors prompted Chapman & Stauf-fer (1981) to propose that S. transitionalis exists only as a refugial relict within the southern parts of its range. More recently, however, the taxonomic status of S. transitionalis has been ques-tioned by the finding of two distinct chro-mosomal races within its presumed geo-graphic range; a northern race characterized
Systematics and biogeography of the New England cottontail, Sylvilagus transitionalis (Bangs, 1895), with the description of a new species from the Appalachian Mountains
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