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

## TL;DR

A new cryptic spider species, A. ramirezae, was discovered in California coastal dunes using genomic and morphological data.

## Contribution

The discovery of a new cryptic spider species using integrative species delimitation methods.

## Key findings

- Phylogenetic analysis identified three lineages within Aptostichus simus.
- A novel cryptic species, A. ramirezae sp. nov., was validated through genetic and morphological analyses.
- The species are endemic to threatened coastal dune habitats in California and Baja California.

## Abstract

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.

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
. The species validation step supported the discovery of a novel cryptic species, A. ramirezae sp. nov., and potential incipient species.