Patterns and Processes Shaping Avian Diversity in the Hawaiian Islands

Abstract

Species are fundamental units of biology. However, the way we define the boundaries between species is a topic of much debate. The process of defining species limits, also known as species delimitation, has historically relied heavily on one factor: reproductive isolation. The importance of reproductive isolation in the history of speciation research is hard to overstate. Most contemporary evolutionary biologist, however, accept that reproductive isolation is not the only thing that matters for species delimitation. Moreover, recognizing that species boundaries are not neatly defined, along with technological and computational advancements, has driven a conceptual shift in our understanding of the formation and maintenance of species boundaries. Researchers are now able to probe the patterns and processes driving speciation in new ways. Among the most important paradigm shifts has been a broad implementation of the Multispecies Coalescent (MSC) framework. Under the MSC conceptual framework we are no longer limited by the strict requirement of reproductive isolation (or any other single factor), but instead aim to understand the genetic history of individuals within populations. In my dissertation, I use MSC-based methods to investigate species delimitation patterns and the speciation processes across different levels of evolutionary divergence and taxonomic breadth. In the first dissertation chapter, I used data from over a century of mating trials in Drosophia flies and contemporary DNA sequence data to determine if species delimited based on reproductive isolation are the same as those identified using a MSC method. In the second dissertation chapter, I obtained DNA sequence data from thousands of genetic markers to and sophisticated phylogenetic methods to determine the evolutionary history for an endemic group of birds known collectively as ‘Elepaio. For the third chapter, I obtained whole genome sequence data from a single species from the Hawaiian honeycreeper radiation, ‘Apapane, to investigate how genomic differentiation may influence the early stages of the speciation process.