Species Delimitation and Diversification History in Rhinoceros Beetles: How Many and Why So Many Species?

[摘要] I address two grand challenges in biology – species delimitation and speciation process. Additionally, I attempt to bridge the gap between macro- and micro-evolutionary studies. The characteristics of two groups of rhinoceros beetles (genus Dynastes and Xylotrupes) make them ideal for addressing these questions – geographically widespread taxa with local morphological forms – also make them challenging to study. These groups exhibit inconsistency in taxonomic designations and their geographic distributions imply complex historical processes in their diversification process. My research highlights both the power, but also the necessity, of an integrative framework that considers different data types, as well as quantitative approaches to test different hypotheses about species boundaries and the diversification process. For example, my first chapter revealed the arbitrariness in taxonomic decisions, even between closely related taxa from the same lineage, by demonstrating that species boundaries were statistically equivalent among taxa even though some were assigned as subspecies. By establishing this taxonomic foundation, my studies on the effects of ecological and geographic isolation on species diversification in the following chapters avoid the biases introduced by taxonomic ambiguity and inconsistency. In my second chapter, I show that the effects of habitat stability/instability outweighs the contributions of geological events that connect previously isolated biotas in promoting rapid diversification in Hercules beetles. Following the general theme of the contribution of different barriers to divergence, in Chapter 3 I test whether their effects are similar across different levels of biological organization – that is, in the structuring of patterns of genetic diversity among population, species, and faunal communities. This work shows that oceanic barriers between landmasses in the Indo-Australian Archipelago delineates zoological regions by structuring distinct faunal communities and promotes population subdivision in Xylotrupes beetles. However, the rate of species diversification is associated with shifts in forest fragmentation across geological times. As such, this work highlights the decoupling of processes contributing to micro- and macroevolutionary patterns, which only became evident because of my integrative approach that involves consideration of alternative mechanisms and study of divergence at multiple levels of biodiversity.

[发布机构] University of Michigan

[效力级别] diversification

[关键词] Species delimitation;diversification;microevolution;macroevolution;niche modeling;beetle;Ecology and Evolutionary Biology;Science;Ecology and Evolutionary Biology