Scientists at the University of California, Davis have identified a new species of trapdoor spider in California’s coastal sand dunes. The species, named Aptostichus ramirezae, is closely related to Aptostichus simus, which ranges from Monterey to Baja California, Mexico.
The research was published in Ecology and Evolution. Senior author Jason Bond, a professor in the UC Davis Department of Entomology and Nematology, stated: “While there are over 50,000 species of spiders worldwide, there are probably hundreds of thousands left to be discovered, even along the coast where new spider species may be hiding just underfoot of California beachgoers.”
Trapdoor spiders are small and secretive relatives of tarantulas. Females spend their lives underground in silk-lined burrows with camouflaged doors. They emerge only when prey comes close enough.
“There are now four known species of trapdoor spiders in California that live exclusively in coastal dune habitats,” said Emma Jochim, corresponding author and doctoral student at UC Davis. “The one we were looking at as part of this study was the most widespread, ranging from Moss Landing near Monterey down to Baja California — which is a pretty wide range for a trapdoor spider, given that they don’t easily leave their burrows to disperse.”
Jochim and colleagues analyzed genomic DNA from specimens across this range. According to Bond’s long-standing suspicion, what appeared as one species actually consisted of cryptic species—organisms that look similar but are genetically distinct.
Researchers also examined the distribution patterns and reproductive isolation between these groups. Jochim explained: “Based on what we know about their natural history and lifestyles, they’re not going to be able to disperse to different coastal dunes to reproduce and ‘mix’ with each other.”
Jason Bond named the newly discovered brown spider Aptostichus ramirezae after Martina Giselle Ramirez, dean at California State University Stanislaus and former biology professor at St. Norbert College. Ramirez has contributed significantly to early research on trapdoor spider genetics and promoted diversity among STEM students.
Both Aptostichus simus and Aptostichus ramirezae inhabit shrinking coastal dune habitats due to development, erosion, wildfire, and sea-level rise. Some populations also exist on the Channel Islands.
“They’re definitely at risk, especially the lineage Aptostichus simus,” Jochim said. “The new species has a much wider range, but Aptostichus simus is now really only found in San Diego, and projections for sea-level rise in that area are very grim. These spiders are not really able to adapt that quickly to new habitats.”
Understanding genetic differences helps scientists prioritize conservation efforts for vulnerable populations. Jochim noted: “If we don’t know how many species are in an area or understand the patterns of genetic diversity between populations, we don’t really know what areas would be most important for conservation efforts.”
James Starrett and Hanna R. Briggs from UC Davis also contributed as authors on this study. The National Science Foundation supported the research.
