UC Davis researchers discover new species of coastal spider, just in time for Halloween

Emma Jochim knew she wanted to study how arachnids evolve as part of her Ph.D. She decided to study trapdoor spiders because they live at the beach.

In the course of her field work, she said, “I’ve been to every coastal dune system on the coast of California to collect … It’s a wonderful time.”

In the dunes between Monterey and Mexico’s Baja California, Jochim and her coauthors discovered a new species of spider that until now has been hidden in plain sight: Aptostichus ramirezae. The new species was announced in Ecology and Evolution.

Previously, these spiders — brown, cute and around the size of a quarter — were thought to be Aptostichus simus, a close relative and lookalike. Researchers suspected they might be distinct, so they analyzed genetic material to distinguish between the two species.

“We knew that these lineages across the coast of California were really different from each other and had been separated for a very long time,” said Jochim, a researcher in the Department of Entomology and Nematology at UC Davis.

The species share similar life histories and ecological roles — preying on arthropods like beetles in coastal dunes — but they don’t interbreed, partly because they rarely move far from their burrows.

“The females never leave their burrows, only the males do,” Jochim said.

Partially because moving from one beach to another would be almost impossibly hard.

“Especially because there’s a lot of rocky coastline in between the different populations,” Jochim said. The spiders can’t live on the rocks, only in sandy dunes.

To locate them, she looks for slopes covered in native plants. The spiders don’t care for European beachgrass or iceplant, originally from South Africa.

“We start digging at the bottom of the hill and as the sand falls down, the burrow — if it’s present — will kind of flop over,” Jochim said. “It looks like a sand-covered sock.”

These elusive spiders are related to tarantulas, which also make burrows. But trapdoor spiders take the engineering a step further, camouflaging the entrances to their burrows.

The hinge of the door, Jochim explained, is made of silk. The door helps regulate temperature and humidity in the burrow.

“It works opposite of what you would imagine a trap door to do,” she said. “Prey doesn’t fall into the burrow from the door, but the spider lunges out from it to capture prey and then goes back in the burrow.”

The spiders pose no risk to humans, Jochim said. Though our activities can pose a risk to them.

“These spiders are not scary,” she said. “They mind their own business and [generally] stay in their burrows … They live in a really important and fragile ecosystem — the coastal dunes of California. So, it’s really important to protect their habitat.”

Development, erosion and sea level rise threaten dunes. Knowing which species are in an area can help conservationists focus their efforts on preserving habitat.

Professor Jason Bond, who heads Jochim’s research group, chose the spider’s name. He’s named several species after celebrities, musicians and politicians, including Aptostichus stephencolberti or Myrmekiaphila neilyoungi and Aptostichus barackobamai.

This new species is named for Martina Giselle Ramirez, dean of the College of Science at California State University, Stanislaus and formerly dean of natural sciences and biology professor at St. Norbert College.

“Ramirez is a highly regarded arachnologist who pioneered early works on trapdoor spider population genetics and has championed underrepresented students in STEM disciplines,” UC Davis said in a statement.