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This pseudoscorpion is a Portuguese cave superstar.

A. Sofia/Natural History Museum of Denmark

Portugal joins world’s hot spots for cave biodiversity

A decade ago, cave biology was a subject few Portuguese ever talked about. Now, the bizarre creatures that inhabit the dark underworld are becoming a source of national pride, says Ana Sofia P. S. Reboleira, a biologist with the Natural History Museum of Denmark at the University of Copenhagen. That’s in large part thanks to her efforts, which have resulted in a dramatic increase in the number of Portuguese caves surveyed for biological life. She and others have identified so many novel species that call Portugal’s caves home that this tiny Mediterranean country would qualify as a biodiversity hot spot for cave organisms—if the field hadn’t recently changed its criteria. Still, in recognition of the nation’s growing interest in the underworld, Portugal recently built a lab and visitor center over one of its more notable caves.

A Portuguese native, Reboleira traces her love of caves to a trip to a commercial cavern with her parents at age 6. At 14, she took up caving as a hobby. While studying biology in college, she realized that she could blend her passion for deep dark places with her love of animals by becoming a cave biologist. At about the same time, David Culver, a cave expert at American University in Washington, D.C., surveyed the world’s cave literature. With the help of colleagues, he then came up with the first list of cave biodiversity hot spots—those with at least 20 organisms specialized for subterranean life, according to the criteria they settled on. (Caves are much less diverse than most surface ecosystems, where a biodiversity hot spot is defined by the presence of hundreds of species crowded into an area.) With further work, Culver and other cave biologists determined there existed a “ridge” of subterranean biodiversity that extended from the Spanish-French border through Slovenia and other places in the Balkans.

At that time, Portugal didn’t rank high when it came to cave biodiversity, but Reboleira thought her country could do better—almost no one there had worked on cave organisms since the early 1960s. So for her graduate studies, she extensively surveyed organisms in Portuguese caves, and for a decade recruited volunteers and other researchers to her cause. In 2014, the Portuguese government opened a “Troglobiário,” a subterranean laboratory and visitor center built over Algar do Pena, a cave unearthed in a quarry in 1985 in central Portugal. Already about 3500 visitors a year have the chance to see cave animals and learn about the limestone formations, called karst, that form such caves.  

Last week, at the 2016 International Conference on Subterranean Biology meeting in Fayetteville, Arkansas, Reboleira proudly provided an update on Portugal’s subterranean fauna. She noted a cave in southern Portugal that would on its own fit Culver’s definition of a cave biodiversity hot spot—it contains 22 cave-limited species, some occurring nowhere else in the world. One unique species is a quarter-sized pseudoscorpion (see image, above) that is an order of magnitude larger than typical pseudoscorpions. Another, a flattened invertebrate called an isopod, is the largest terrestrial isopod known in Europe. Caves elsewhere around the country were also revealing new organisms, Reboleira reported. “The more we look, the more we describe,” she says.

That’s good, because earning the cave “hot spot” label has become harder, Culver says. Since coming up with the 20 cave organisms standard—one that now scores of caves meet —he and his colleagues now require at least 25 terrestrial cave-specific species in a location or at least the same number of aquatic species. And Portugal has new countries competing for subterranean biology honors. At the meeting, researchers from places such as Oman, the Philippines, and China described rapid progress identifying new cave species in their respective countries. Until 10 years ago, researchers had described just 21 obligate cave organisms from all of Southeast Asia, says Stefano Taiti, a cave biologist from the Institute of Ecosystem Study in Florence, Italy. Now, dozens of cave fish are known from China alone, he notes. And at the meeting, Chinese researchers showed an equally impressive array of newly described cave beetles. Time for Reboleira to head back into Portugal’s caverns.