Last updated: January 20, 2025
Article
Scientists Solve One Spider Mystery—and Find Another
Bucking the trend for most cave-dwelling animals, one species of cave spider is widely dispersed across the U.S. Scientists wonder how.
By the editors of Park Science magazine
Image credit: Matthew L. Niemiller
Caves can serve as an island-like habitat for the animal species that call them home. Many are troglobionts—species adapted to living in caves. For example, they adapt to darkness through successive generations by going blind. These adaptations restrict their movement, and many species aren’t able to leave the cave. Such isolated populations of the same species often develop distinct genetic differences over time. In the process, they become different subspecies.
But one cave-dwelling spider, Phanetta subterranea, is a remarkable exception. This spider is found in more caves than any other troglobiont in North America. A group of scientists studied the genetic makeup of different populations of P. subterranea. They wanted to find out whether each population was a different subspecies as might be expected. The results of their work were published in the journal, Subterranean Biology, in December 2024.
Between 1998 and 2023, the researchers compared the DNA of specimens of P. subterranea from 40 different caves in seven U.S. states. They found that specimens collected up to 600 kilometers (about 372 miles) apart had surprisingly low genetic diversity. The researchers conclude there are likely no subspecies of P. subterranea. They offer suggestions for solving the mystery of how these cave spider populations came to live in so many geographically widespread caves.
Kennedy and others. 2024. Remarkably low genetic diversity in the widespread cave spider Phanetta subterranea (Araneae, Linyphiidae). Subterranean Biology 50: 105-118.