A Col­lec­tion of News by Moos


Genetic analy­sis of New World birds con­firms the­ory of speciation

pub­lished 24 June 2017 | mod­i­fied 24 June 2017

Biol­o­gists have always been fas­ci­nated by the diver­sity and change­abil­ity of life on Earth and have attempted to answer a fun­da­men­tal ques­tion: How do new species originate?

An implicit assump­tion in the dis­ci­pline of spe­ci­a­tion biol­ogy is that genetic dif­fer­ences between pop­u­la­tions of ani­mals and plants in a given species are impor­tant dri­vers of new species for­ma­tion and are a key to under­stand­ing evo­lu­tion. But that assump­tion has never been rig­or­ously tested, until now, accord­ing to Uni­ver­sity of Michi­gan evo­lu­tion­ary biol­o­gist Michael Harvey.

new world birds tree of life
A cir­cu­lar phy­lo­ge­netic tree of the 173 bird species included in the study and col­ored accord­ing to the rates they pro­duce species over deep time. Sur­round­ing the tree are tri­an­gles depict­ing the rate of pop­u­la­tion dif­fer­en­ti­a­tion within each species.
Image credit: Michael Har­vey, PNAS

Har­vey and col­leagues com­piled and analysed an unprece­dented data set con­tain­ing genetic sequences from 17,000 indi­vid­u­als in 173 New World bird species, rang­ing from ducks and owls to swal­lows and spar­rows. They demon­strated that species show­ing faster rates of genetic dif­fer­en­ti­a­tion between pop­u­la­tions are more likely to pro­duce greater num­bers of species over long evo­lu­tion­ary timescales. The results are pub­lished online on 30 May in the jour­nal Pro­ceed­ings of the National Acad­emy of Sci­ences.

Our results are of fun­da­men­tal sig­nif­i­cance because there are researchers across the world study­ing spe­ci­a­tion, and many of them inves­ti­gate genetic dif­fer­ences between pop­u­la­tions that are in the process of form­ing new species,” said Har­vey, a post­doc­toral fel­low in the Depart­ment of Ecol­ogy and Evo­lu­tion­ary Biol­ogy, in the lab­o­ra­tory of Daniel Rabosky. “These researchers assume those genetic dif­fer­ences are impor­tant for evo­lu­tion, but this has never been shown in a sat­is­fac­tory way.”

We are the first to show that the dif­fer­ences between pop­u­la­tions stud­ied by spe­ci­a­tion biol­o­gists have been fun­da­men­tal deter­mi­nants of the for­ma­tion of the diver­sity of life

Michael Har­vey, lead author, Depart­ment of Ecol­ogy and Evo­lu­tion­ary Biol­ogy, Uni­ver­sity of Michi­gan, Ann Arbor, USA.

The researchers mea­sured the rate at which genetic dif­fer­ences accu­mu­lated between pop­u­la­tions in each of the 173 bird species. They then com­pared the rate of pop­u­la­tion dif­fer­en­ti­a­tion to the prob­a­bil­ity that each bird species would form new species over time. This prob­a­bil­ity was based on the evo­lu­tion­ary track record of each species: How many species did its ances­tors pro­duce over the his­tory of avian diversity?

They found that the rate of genetic dif­fer­en­ti­a­tion within species is pos­i­tively cor­re­lated with the rate of new species for­ma­tion. The two rates were more tightly linked in trop­i­cal species than in tem­per­ate species.

The study pro­vides the first large-​scale test of the link between pop­u­la­tion dif­fer­en­ti­a­tion rates and spe­ci­a­tion rates. The results con­firm the evo­lu­tion­ary impor­tance of pop­u­la­tion genetic differentiation.

How­ever, genetic dif­fer­ences do not guar­an­tee evo­lu­tion­ary suc­cess. Har­vey and his col­leagues found that the cor­re­la­tion between pop­u­la­tion genetic dif­fer­en­ti­a­tion and species for­ma­tion was imper­fect, which sug­gests that other fac­tors besides dif­fer­en­ti­a­tion may be impor­tant in deter­min­ing how many new species are produced.

They also found that the emer­gence of new pop­u­la­tions within a species occurs at least three times faster than new species develop, sug­gest­ing that most dif­fer­ences between pop­u­la­tions will not last long enough to impact species diversity.

Over­all, how­ever, the study con­firms the long-​held assump­tion that the genetic dif­fer­ences between pop­u­la­tions of a given species might pre­dict its prob­a­bil­ity of con­tribut­ing to the diver­sity of life,” Har­vey said.

(Source: Uni­ver­sity of Michi­gan news release, 30.05.2017)

Goal: 7000 tigers in the wild

Tiger range countries map

Tiger map” (CC BY 2.5) by Sander­son et al., 2006.

about zoos and their mis­sion regard­ing breed­ing endan­gered species, nature con­ser­va­tion, bio­di­ver­sity and edu­ca­tion, which of course relates to the evo­lu­tion of species.
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