UC Davis

Spiders placed in the infraorder Mygalomorphae (tarantulas, trapdoor spiders and their kin) are generally recognized as an ancient cosmopolitan lineage that has persisted for over 250 million years. Mygalomorph life history traits that include limited dispersal abilities, habitat specialization, and site fidelity altogether make them ideal organisms for studying speciation pattern and process, phylogeography, and adaptation. Evolutionary studies of mygalomorphs at both shallow and deeper phylogenetic levels have been limited prior to the advent of next generation sequencing approaches, with the majority of such studies relying on morphological characters or limited targeted locus approaches for phylogenetic reconstruction. Thus, it is imperative to implement larger genomic-scale datasets for confident reconstruction of relationships. My dissertation focuses on species delimitation in two trapdoor spider groups, Antrodiaetus unicolor complex and Aptostichus icenoglei sister species complex, and evaluation of interspecific relationships within the genus Aptostichus. To address species boundaries in the A. unicolor species complex, I implemented genomic-scale data (i.e., restriction-site associated DNA sequencing, RADseq) in conjunction with morphological, behavioral, and ecological data to evaluate cohesion species identity (Chapter I). Similarly, assessing species boundaries in the Aptostichus icenoglei sibling species complex involved a target capture approach for subgenomic data (i.e., ultraconserved elements, UCEs) and ecological data to evaluate genetic and ecological exchangeability, as per the cohesion species-based delimitation approach from a previous study (Chapter II). Lastly, to resolve interspecific relationships within Aptostichus, I used a sequence capture method (i.e., UCEs) to generate molecular data in conjunction with morphological data for a combined-evidence phylogeny (Chapter III). These chapters all have the same overarching theme: to understand the forces underlying divergence between units of diversity and how those units are defined.