Narrator: This is Science Today. A recent study of Hawaiian spiders documents how 16 species descended from a common ancestor about five million years ago. Biologist Rosemary Gillepsie of the University of California, Berkeley says studying the evolution of spiders on the Hawaiian Islands was particularly nice, since there's a built-in, chronological system there.

Gillepsie: You've got the oldest island at Kaui at five million years and then progressively younger islands, so you've got this whole progression of islands at different ages and you can see communities at different ages.

Narrator: Gillespie conducted DNA detective work to follow the radiation of the Hawaiian Long Spider from a single ancestor.

Gillespie: The whole phenomenon depends on very few colonists ever reaching the islands. So you get one animal getting there and there's nothing else there. So, it diversifies into multiple species to fill the empty niches in the communities there.

Narrator: For Science Today, I'm Larissa Branin.