July 24, 2012 How quickly can new species arise? In as little as
6,000 years, according to a study of Australian sea stars.
"That's unbelievably fast compared to most organisms," said Rick
Grosberg, professor of evolution and ecology at UC Davis and
coauthor on the paper published July 18 in the journal
Proceedings of the Royal Society B. Grosberg is interested in
how new species arise in the ocean. On land, groups of plants
and animals can be physically isolated by mountains or rivers
and then diverge until they can no longer interbreed even if
they meet again. But how does this isolation happen in the wide-
open ocean? Grosberg and colleagues studied two closely related
"cushion stars," Cryptasperina pentagona and C. hystera, living
on the Australian coast. The animals are identical in appearance
but live in different regions: Hystera occurs on a few beaches
and islands at the far southern end of the range of pentagona.
And their sex lives are very, very different. Pentagona has male
and female individuals t