Media Releases

New song about evolution, from the world’s sexiest birds

December 7, 2010

TORONTO, ON – While the trop­ics are home to the vast major­i­ty of plant and ani­mal species on Earth, new research on song­birds sug­gests evo­lu­tion actu­al­ly hap­pens faster in places that are locat­ed far away from the equa­tor.

Jason Weir, assis­tant pro­fes­sor of evo­lu­tion­ary biol­o­gy at the Uni­ver­si­ty of Toron­to Scar­bor­ough (UTSC), mea­sured the dif­fer­ences in length and com­plex­i­ty of song in more than 100 close­ly relat­ed pairs of song­bird species, in order to esti­mate how fast evo­lu­tion might be occur­ring between each pair.
Con­ven­tion­al wis­dom has held that speciation—the process by which new species are created—occurs in trop­i­cal regions at high­er rates than any­where else, explain­ing why the trop­ics are such a hotbed of bio­log­i­cal diver­si­ty.

But when Weir and his col­league, David Wheat­croft at the Uni­ver­si­ty of Chica­go, plot­ted their results against the loca­tions where the birds are found, they dis­cov­ered the far­ther away a species was from the equa­tor, the faster the evo­lu­tion­ary change.
“Our results show the fastest rates of song evo­lu­tion in places where diver­si­ty is rel­a­tive­ly low,” says Weir. “This is sur­pris­ing, because it sug­gests that a fast evo­lu­tion­ary pace does not dri­ve high bio­di­ver­si­ty. We are going to have to rethink why places like the Ama­zon have so many species.”

One expla­na­tion may lie with the sex­u­al behav­iour of female birds. In high­er lat­i­tudes, breed­ing sea­sons become short­er, and females must select their mates much faster than they do at the equa­tor. This means there is a great deal of pres­sure on the males to evolve high­ly dis­tinct and com­plex songs in order to attract these high­ly moti­vat­ed females.

“Females are always look­ing for the sex­i­est singers,” says Weir. “But at high­er lat­i­tudes, with short­er breed­ing sea­sons, females may not have time to eval­u­ate the males’ oth­er qual­i­fi­ca­tions as they do in the trop­ics. This pres­sure would like­ly dri­ve the rapid evo­lu­tion of com­plex­i­ty in bird­song. The high­er the lat­i­tude, the sex­i­er the singers have to be.”

The study is cur­rent­ly pub­lished online in the Pro­ceed­ings of the Roy­al Soci­ety B.


For more infor­ma­tion, please con­tact:

Jason Weir, lead author

Karen Ho
Media and com­mu­ni­ca­tions assis­tant
Uni­ver­si­ty of Toron­to Scar­bor­ough