Evolution in Sundaland: insights from comparative phylogeography of Rattus and Sundamys rats

Abstract

The tropical bioregion of Sundaland, Southeast Asia, is a major hotspot of world biodiversity. Its complex geological history lays out an excellent scenario to study evolution. However, the interpretations of Sunda biogeography patterns for mammals has been limited due to (1) the uncertain taxonomy for most small mammals and (2) biased or incomplete sampling of certain regions (e.g. Sumatra). I combined a taxonomic approach followed with extensive sampling in the field and from zoological collections for well-represented groups of rats (Sundamys and Rattus) as models to evaluate the interplay of Plio-Pleistocen changes in the diversification patterns of mammals in Sundaland. I use genetics in combination with morphology and ecology to look at diversification both within and between species in these two genera to test biogeographic and other evolutionary hypotheses. Chapter 1, Introduction, I describe the theoretical framework of my study, introduce the biological study models, set the hypotheses underlying my research and overview the methodological approach to tackle these questions, including methodological challenges and outcomes. Chapter 2, I study the role of tropical mountains as interglacial refugia. I use genetics to evaluate the effect of post-Last Glacial Maximum (~21 Kya) changes on the demographic history of Rattus baluensis, a rat endemic to mountains above 2000 m in northern Borneo. Chapter 3, I discuss the phylogenetic relationships of Sundaic endemic Rattus with focus on the evolution of montane lineages. Chapter 4, I generate a complete phylogeny of the genus Sundamys, reclassify Rattus annandalei as Sundamys annandalei, and discuss its evolutionary implications. Chapter 5, I construct a comprehensive phylogeographic study of Sundamys, a rat genus endemic to Sundaland, as a model to evaluate Plio-Pleistocene changes on vertebrate diversification in this region.