In a new paper published in the Jan. 16 issue of Science, University of California, Berkeley, biologist Rosemary Gillespie uses genetic detective work to describe how these spiders, otherwise common streamside inhabitants throughout the world, diversified to fill an entire spectrum of habitats in the Hawaiian Islands. Along the way, she challenges the assumption that the formation of communities through evolutionary processes in the remote Hawaiian archipelago is different from the way communities are assembled through immigration on a large continent.
"The Hawaiian Islands are often considered to be so unusual and remote that what happens there cannot be applied to other places," said Gillespie, professor of insect biology, director of the Essig Museum of Entomology at UC Berkeley and author of the paper. "What I'm showing is that the same kinds of things happen on these islands as elsewhere; it's just that evolution plays more of a role."
Because Hawaii consists of a chain of islands that formed chronologically, Gillespie was able to study the spiders' adaptive radiations over time in what she calls a "natural time-series laboratory" of evolution. The oldest island, Kauai, was formed 5 million years ago, followed in age by Oahu, Molokai, Lanai, Maui and finally the big island of Hawaii, the youngest island at less than 1 million years old.
Gillespie found 16 species of Tetragnatha spiders, all of which have abandoned web building, actively hunt their prey and have long spines along their legs. By examining the spiders' DNA, she determined that the 16 species descended from one commo
Contact: Sarah Yang
University of California - Berkeley