AboutZoos, Since 2008


Bird colour vari­a­tions speed up evolution

pub­lished 14 May 2012 | mod­i­fied 25 July 2012

Researchers have found that bird species with mul­ti­ple plumage colour forms within in the same pop­u­la­tion, evolve into new species faster than those with only one colour form, con­firm­ing a 60 year-​old evo­lu­tion theory.

The global study used pub­licly avail­able infor­ma­tion from bird­watch­ers and geneti­cists accu­mu­lated over decades and was con­ducted by Uni­ver­sity of Mel­bourne sci­en­tists Dr Devi Stuart-​Fox and Dr Andrew Hugall (now based at the Mel­bourne Museum) and is pub­lished in the jour­nal Nature.

The link between hav­ing more than one colour vari­a­tion (colour poly­mor­phism) like the iconic red, black or yel­low headed Goul­dian finches, and the faster evo­lu­tion of new species was pre­dicted in the 1950s by famous sci­en­tists such as Julian Hux­ley, but this is the first study to con­firm the theory.

Gouldian finchGrey goshawk

We found that in three fam­i­lies of birds of prey, the hawks and eagles, the owls and the night­jars, the pres­ence of mul­ti­ple colour forms leads to rapid gen­er­a­tion of new species
Dr Devi Stuart-​Fox »

By con­firm­ing a major the­ory in evo­lu­tion­ary biol­ogy, we are able to under­stand a lot more about the processes that cre­ate bio­di­ver­sity said Dr Devi Stuart-​Fox from the University’s Zool­ogy Depart­ment. “Well known exam­ples of colour poly­mor­phic species in these fam­i­lies include the Aus­tralian grey goshawk which has a grey and pure white form, the North Amer­i­can east­ern screech owl and the Antil­lean nighthawk, each with grey and red forms.”

The team focused on birds because although colour poly­mor­phism occurs in many ani­mals (such as fish, lizards, but­ter­flies and snails), there is a wealth of infor­ma­tion on colour vari­a­tion in birds, as well as on species clas­si­fi­ca­tion (tax­on­omy), partly thanks to bird­watch­ers or ‘twitch­ers’. “We looked at five bird fam­i­lies with a high pro­por­tion of colour poly­mor­phism and com­pared their rates of evo­lu­tion with those with only one colour form,“ Dr Stuart-​Fox said.

By mod­el­ing evo­lu­tion­ary rates using pub­licly avail­able genetic infor­ma­tion accu­mu­lated over a quar­ter of a cen­tury, the study found that colour poly­mor­phism speeds up the gen­er­a­tion of new species. Colour poly­mor­phic species tend to evolve into species with only one colour form (monomor­phic), explain­ing why exist­ing species with dif­fer­ent colour forms are rel­a­tively young and also rare. The study found that colour poly­mor­phic species were younger not only in the birds of prey but in the song­birds, which account for more than half of the world’s bird species.

Using many decades of nat­ural his­tory infor­ma­tion and 25 years of genetic sequence infor­ma­tion we were able to gen­er­ate the mas­sive fam­ily trees, such as a tree of more than four thou­sand song­birds, needed to model rates of bird evo­lu­tion in this study
Andrew Hugall »

Study co-​author Dr Andrew Hugall noted that when sci­en­tists like Julian Hux­ley pro­posed that colour poly­mor­phism speeds up the gen­er­a­tion of new species over half a cen­tury ago, they did not have the huge amounts of data needed to sup­port it.

Now that we’ve iden­ti­fied this pat­tern for the first time, our next step is to test some of the expla­na­tions pro­posed for why colour poly­mor­phism leads to accel­er­ated evo­lu­tion.”

The above news item is reprinted from mate­ri­als avail­able at the Uni­ver­sity of Mel­bourne via Sci­enceAl­ert. Orig­i­nal text may be edited for con­tent and length.

(Source: The Mel­bourne News­room, 10.05.2012)

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