Habitat driven diversification in small mammals of tropical east Asia

Abstract

Tropical east Asia is a major biodiversity hotspot with a complex geological and climatic history, providing an excellent system to study evolution. In this thesis I combine material collected in the field with genetic samples and morphometric data from museum specimens in order to evaluate the role of geological and environmental changes in the diversification of small mammals in tropical east Asia. In Chapter 1, I assess phenotypic variation across tropical elevational gradients in the mountain treeshrew Tupaia montana, a Borneo endemic. In Chapter 2, I estimate the diversification timing of Sunda squirrels (Sundasciurus), correlate it with paleogeographic and paleoclimatic evidence and review the taxonomy of the Sundasciurus lowii species complex. In Chapter 3, I study the diversity and diversification of Sundaland’s Crocidura shrews, with an emphasis on the species of Borneo. In Chapter 4, I evaluate patterns of genetic and phenotypic divergence across the biogeographic break of the Isthmus of Kra in four small mammals with different life-history traits. My results reveal an important role for ecology in driving diversification in Sundaland, suggest a strong east-west differentiation in Indochina, support Borneo as a centre of in situ diversification, and indicate that the pattern observed in the distributions of so many species -turnover at the Isthmus of Kra s. l.- are mirrored in others at the intraspecific level. Finally, this thesis highlights an important Linnean shortfall in tropical east Asian small mammals and the necessity of additional specimen collection and taxonomic revisions.