Combined-evidence phylogeny, habitat evolution, and biogeography of the trapdoor spider genus Aptostichus (Araneae: Mygalomorphae: Euctenizidae)

The trapdoor spider genus Aptostichus comprises forty-one species, most of which are primarily restricted to the California Floristic Province (CAFP), a known biodiversity hotspot; however, four species inhabit Nevada, Arizona, and one ostensibly known from Oaxaca, Mexico. Aptostichus species range widely in size and coloration as well as occupy a variety of habitats ranging from arid deserts, coastal dunes, and high elevation alpine habitat. Additionally, Aptostichus has a relatively high amount of species diversity when compared to other euctenizid genera and many other mygalomorph taxa. High species and habitat diversity underscore a putative pattern of an adaptive radiation in the genus, making them ideal taxa for investigating speciation pattern and process, character evolution, and adaptation. A previous revisionary study reconstructed evolutionary relationships based on morphological data and, although a fully resolved phylogeny was proposed, much uncertainty in interspecific relationships remain. Building on this previous study, we increased taxon sampling and used a sequence capture method (i.e., ultraconserved elements, UCEs) to generate subgenomic phylogenetic data. We were also successful in sequencing UCEs from historical ethanol-preserved museum specimens; thus, we were able to include a few rare and presumed extinct Aptostichus species in both molecular and morphological datasets. From our datasets we established a robust ‘combined-evidence’ phylogeny to provide a framework for exploring evolutionary diversification across the CAFP landscape, specifically evaluating the evolution of different habitat types.