Scientists at the University of California, Davis have identified a new species of trapdoor spider living in California’s coastal sand dunes. The newly named Aptostichus ramirezae is closely related to Aptostichus simus, which ranges from Monterey to Baja California, Mexico. The discovery was published in the journal Ecology and Evolution.
“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,” said Jason Bond, senior author and professor in the UC Davis Department of Entomology and Nematology.
Trapdoor spiders are small relatives of tarantulas that live underground for most of their lives. Females create silk-lined burrows with camouflaged doors and emerge only to catch prey that comes near. According to Emma Jochim, corresponding author and doctoral student at UC Davis, “There are now four known species of trapdoor spiders in California that live exclusively in coastal dune habitats. 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 her team used genomic DNA analysis on samples collected throughout this range. Bond had suspected for some time that what appeared to be one species might actually represent several cryptic species—species that look nearly identical but differ genetically.
Researchers also studied the distribution patterns of these spiders. Cryptic species tend not to interbreed because they remain isolated from each other by geography and lifestyle. “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,” Jochim explained.
The new species was named by Professor Bond 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 has supported underrepresented students in science fields.
Both Aptostichus simus and Aptostichus ramirezae inhabit shrinking coastal dune environments from central California through northern Baja California—including areas such as the Channel Islands—due to factors like development, erosion, wildfire, and rising sea levels. “They’re definitely at risk, especially the lineage Aptostichus simus,” said Jochim. “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.”
Studying genetic differences among these spiders can help scientists determine which populations require urgent conservation measures. Jochim emphasized: “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 co-authors on this study; funding was provided by the National Science Foundation.
