Speciation Pattern and Process in the California Coastal Dune Endemic Trapdoor Spider Aptostichus simus (Mygalomorphae: Euctenizidae) and Description of a New Cryptic Species.

The application of genomic and sub-genomic data in species delimitation has facilitated the discovery of cryptic species. As the name implies, cryptic species are difficult, if not impossible, to distinguish based on morphology alone. The integrative species delimitation process employed herein comprises three steps: species discovery, species validation, and species description. Phylogenetic analysis of sub-genomic data revealed three major lineages within the trapdoor spider Aptostichus simus. These lineages identified candidate species that were then tested using further genetic and morphological analyses. The species validation step supported the discovery of a novel cryptic species, A. ramirezae sp. nov., and potential incipient species. Aptostichus simus and A. ramirezae sp. nov., are endemic to coastal dune habitats in California and Baja California, which face many threats such as erosion, human development, habitat fragmentation, coastal squeeze, and sea level rise. Understanding the patterns of genetic diversity in these species is crucial for informing conservation efforts of both the animals and habitat in which they live.