Abstract
Abiotic forces such as climate and geology often exert an influence on the evolution of organisms, the extent to and manner in which they do so being an intriguing question in evolutionary biology. Such a question is broad and would encompass many differing lines of approach, as well as employ a taxonomic study system that facilitates such inquiry.Such a study system would ideally be a group of related lineages that are old enough to span a variety of geological events and changes, strongly conserved in niche space to limit variability among lineages, be dispersal limited and thus be more affected by changes over generation time, and have a close association with the environment within the niche. Antrodiaetus is a genus of Mygalomorph spider (Antrodiaetidae, Mygalomorphae) whose species possess such qualities, and is thus an ideal taxonomic group for answering questions about how abiotic forces influence evolution. Antrodiaetus is a relatively old genus believed to date back to the Cretaceous Period, and consists of morphologically conserved species that possess strong habitat fidelity. These spiders are believed to be poor natal dispersers, as like most Mygalomorph spiders they do not balloon. Finally, this lineage possesses a disjunct, Holarctic distribution that is typical of other dispersal-limited, old genera from the Holarctic that are restricted in niche space.
The primary goal for this dissertation was to understand the role abiotic forces play in the evolutionary process using Antrodiaetus as a study system. This was done specifically by asking three questions: What are the relationships among species using genomic data? Does cryptic diversity exist within the species-rich Pacific Northwest? How old are the divergences among lineages within Antrodiaetus? With answers to these questions I aimed to resolve long-standing hypotheses about the group and inform our understanding of the role abiotic forces play in the evolutionary history of species.
Overall I have found that the evolutionary history of Antrodiaetus is closely associated with a changing landscape over geological time, and that many of these environmental changes are likely responsible for generating the diversity and distributions within the genus that we see today; an example of which is seen in the “smoking gun” system of “pacificus WEST” and “pacificus SE” which has a vicariant event maintained by the rain shadow of the Coastal and Cascade Ranges. More generally, mountain building in the western Nearctic over time (such as the Laramide Orogeny) likely has created much of the current species diversity. Certainly more work is to be done with this unique and fascinating group, and this dissertation should provide a solid platform upon which to further explore the biology a useful study system.