Molecular Systematics and Historical Biogeography of the Tree Shrews (Tupaiidae).

Abstract

This dissertation examined the molecular systematics and historical biogeography of tree shrews (Tupaiidae). Comparison of cytochrome b sequences and DNA hybridization data suggests that cytochrome b sequences evolved 7.9 to 13.4 times faster than single-copy nuclear DNA. These two data sets are taxonomically congruent. They indicate that the Mindanao tupaiid Urogale everetti is a member of Tupaia, and that there is lineage-based variation in rates of evolution among the tupaiids. A new species of Tupaia from Sarawak (Malaysia), T. stuebingi, was described using morphological, ecological, and cytochrome b sequence data. This lowland species is generally similar in size to the montane species, T. montana. Its coat coloration and fur texture resembles the common species, T. glis. Cytochrome b comparisons show that it is most closely related to T. montana at a proportional distance of 11.1%. Intrafamilial phylogenetic analyses placed the smooth-tailed Dendrogale as the outgroup of Tupaia, and the bushy-tailed Urogale everetti and the pen-tailed Ptilocercus lowii as members of Tupaia. All five taxa in the T. glis species group---belangeri, chinensis, glis, longipes , and salatana---should be recognized as full species based on their large degree of genetic and morphological differentiation, and their geographic separation. Maximum likelihood comparisons yielded three distinct tupaiid clades: a basal clade consisting of Asian mainland taxa, a middle clade of Philippine taxa, and a distal clade of Bornean taxa. This pattern suggests that the Bornean tupaiids originated on the Asian mainland, On Borneo, two phylogeographic patterns---one deep and one shallow---were found, suggesting that the island was colonized repeatedly. Based on cytochrome b data, the sister group of tupaiids is a clade consisting of rabbits, hedgehog, and elephant shrew. However, this sister relationship is likely the result of random long branch attraction between ingroup and distant outgroups. Thus, cytochrome b data cannot resolve the interordinal relationships of tupaiids, and their sister group remains unclear.