Macroevolution of Australian blindsnakes

Abstract

How have different life forms come to be the way they are? Why are some groups remarkably diverse in morphology and ecology while others are not? These are persistent questions in evolutionary biology. Much of the taxonomic richness on our planet is a result of evolutionary radiations, a process by which members of a phylogenetic lineage diversify into many species. In adaptive radiations, species diverge into a variety of forms that allow them to exploit different environment like in the famous radiations of Caribbean anoles, Galapagos finches and African cichlids. On the other hand, in nonadaptive radiations, species diverge with little differentiation in morphology and environment, as exemplified in species with low dispersal abilities such as snails, stick insects, and salamanders. However, cases of nonadaptive radiations on a continental scale have rarely been documented or studied.

Continental Australia is home to many evolutionary radiations from both ancient endemic Gondwana ancestors and more recent immigrants of Asian origin. The island's vast size and diversity of biomes make it a good place to study diversification across a range of habitats over time. Squamate reptiles (lizards and snakes) are a particularly successful group on this continent with over 1000 species described. Some of the most iconic clades show dramatic eco-morphological differentiation, but a few other clades have also diversified in more subtle ways. Blindsnakes in the genus Anilios are a group of morphologically and ecologically conserved fossorial snakes that is distributed across the Australian landscape. However, little is known about their natural history and evolutionary history.

In this thesis I present three empirical studies spanning from phylogenetics to morphology of Australian blindsnakes to understand evolutionary dynamics of this radiation. I compiled molecular, morphological, and environmental data for all Australian blindsnake species and analysed them using a combination of comparative methods to tackle important questions about diversification patterns in Australia. In the first chapter I used molecular data and divergence time estimation methods to infer the phylogenetic relationship between all species and estimate when species diverged from each other. I also identified potential divergent lineages and provide recommendations for further taxonomic investigations. In the second chapter I revisited the historical biogeography of the radiation and used various phylogenetic comparative methods to identify macroecological factors that influenced diversification rates of the radiation. Finally, in the third chapter I examined the eco-morphological variation among Australian blindsnakes and used phylogenetic-based models to infer the dominant mode of speciation. In all these chapters I presented new data and combined currently available methods to extend our understanding of Australian blindsnakes, and provide a series of studies that can be compared to other groups of organisms on our planet. Show more