Scientists have discovered a new trapdoor spider species lurking beneath California’s sandy coastal dunes. This elusive arachnid, found in areas frequented by beachgoers, belongs to a hidden world of spiders that remain largely unknown to science. The discovery offers a fascinating glimpse into the biodiversity that thrives in these fragile dune ecosystems. The study, published in Ecology and Evolution, reveals how much remains to be uncovered—right beneath our feet.
Hidden Hunters Beneath The Sand
The new research, featured in Ecology and Evolution, brings attention to a previously unknown species of trapdoor spider living along California’s coast. Unlike the more familiar web-building spiders, these ground-dwelling predators dig burrows lined with silk and topped with a camouflaged lid, from which they ambush prey. “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 senior author Jason Bond, professor in the UC Davis Department of Entomology and Nematology.
Figure 01: Maximum likelihood phylogram based on minimum 75% locus occupancy concatenated dataset. Shaded boxes correspond to major phylogenetic clades. Bootstrap support values < 100% are labeled, otherwise node support is 100%. Black circles indicate nodes with 100% support from consensus species trees generated with ASTRAL-III with bootstrap resampling run with 100 pseudoreplicates in ASTRAL v5.7.8 Outgroup not shown for display purposes. Acronyms in parentheses next to specimen codes correspond to localities. (see Figures 2 and S1). Subset image shows live Aptostichus ramirezae sp. nov. (BME101034). ( Ecology and Evolution)
The study identifies four known trapdoor spider species native to California’s coastal dunes, each uniquely adapted to its environment.
“There are now four known species of trapdoor spiders in California that live exclusively in coastal dune habitats,” explained Emma Jochim, corresponding author and doctoral student at UC Davis.
The newly described species exhibits an unexpectedly wide distribution, extending from Moss Landing near Monterey down to Baja California.
“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.”
Figure 02: Distribution map of California and Baja California (partial) with localities (and their acronyms) included in genetic analyses. Colors correspond to major phylogenetic clades (see Figure 1). Map made with ArcGIS Online (Esri 2025). ( Ecology and Evolution)
Fragile Web Of Survival
While their range might seem broad, these spiders face a narrowing future. “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 said. This lack of mobility could make them particularly vulnerable to environmental change. Rising sea levels and coastal development threaten their already limited dune habitats.
“They’re definitely at risk, especially the lineage Aptostichus simus,” she added. “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.”
The study emphasizes that these secretive species, while rarely seen, play an integral role in dune ecosystems by maintaining insect populations and supporting biodiversity. Yet, because they are so rarely encountered, their ecological importance has been largely overlooked. The loss of such species could have cascading effects that extend well beyond the dunes themselves.
Mapping The Unknown
Beyond the immediate discovery, the researchers highlight a broader message about biodiversity. “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,” Jochim said. Cataloging such hidden species provides a clearer map of the planet’s biodiversity and reveals which habitats are most at risk.
These insights reinforce a growing call among biologists to study and preserve the world’s lesser-known creatures before they vanish. The coastal dunes of California, though seemingly familiar, remain one of the most mysterious landscapes in the state—where the secrets of evolution lie buried just beneath the sand.