Biogeographical and Evolutionary Relationships Among Central American Small-Eared Shrews of the Genus Cryptotis (Mammalia: Insectivora: Soricidae)

Abstract

Small-eared shrews of the genus Cryptotis have a distribution that extends from southernmost Ontario and across much of the eastern half of the United States south to the northern Andean highlands. The genus attains its greatest diversity in Mexico and Central America, where eight species generally have been recognized. My studies of geographical and elevational distribution and correlated morphological variation indicate that Cryptotis is much more diverse and speciose than previously considered. I recognize 19 species in this same region, and I suggest that there is potential for even greater species-level diversity. This is mostly a result of prehistoric isolation of populations in restricted highland areas, subsequent morphological divergence, and speciation. This brings the total number of species of Cryptotis to 25; there is a total of 3 6 monotypic species and subspecies. Phylogenetic analysis of the genus Cryptotis using a matrix of 19 transformation series indicates three wellsupported lineages occur within the genus: the C. parva group, consisting of C. parva and all of its subspecies; the C. niarescens group, which includes C. magna in addition to species once considered subspecies of C. nicrrescens; and the C. thomasi group, which now includes C. gracilis, C. endersi , and members of the C. mexicana group, as well as most South American species. Relationships among the three lineages are uncertain, but the C nigrescens most likely shares a sistergroup relationship with either the C. parva group or the C. thomasi group. Within the C. nigrescens group C. magna has a sister group relationship with C. mayensis and C. merriami. Biogeography of the genus Cryptotis is complex, and it appears that ancestral patterns of divergence have been obscured by subsequent expansion and contraction of species ranges.