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200923Dec19:24

Feed­ing birds in win­ter speeds up evolution

Infor­ma­tion
pub­lished 23 Decem­ber 2009 | mod­i­fied 29 Decem­ber 2011
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Feed­ing birds in win­ter is a most inno­cent human activ­ity, but it can nonethe­less have pro­found effects on the evo­lu­tion­ary future of a species, and those changes can be seen in the very near term. That’s the con­clu­sion of Schae­fer et al. In their report which shows that what was once a sin­gle pop­u­la­tion of birds known as black­caps (Sylvia atr­i­capilla) has been split into two repro­duc­tively iso­lated groups in fewer than 30 gen­er­a­tions, despite the fact that they con­tinue to breed side by side in the very same forests.

How did this speedy evo­lu­tion come about?

The split that the researchers observed fol­lowed the recent estab­lish­ment of a migra­tory divide between south­west– and northwest-​migrating black­cap pop­u­la­tions in Cen­tral Europe after humans began offer­ing food to them in the win­ter. The two groups began to fol­low dis­tinct migra­tory routes, win­ter­ing in Spain and the United King­dom, and faced dis­tinct selec­tive pres­sures. Under that pres­sure, the two groups have since become locally adapted eco­types. A first step to species dif­fer­en­ti­a­tion which can lead to species sep­a­ra­tion in the end.

The new north­west migra­tory route is shorter, and those birds feed on food pro­vided by humans instead of fruits as the birds that migrate south­west do. As a con­se­quence, birds migrat­ing north­west have rounder wings, which pro­vide bet­ter maneu­ver­abil­ity but make them less suited for long-​distance migra­tion. They also have longer, nar­rower bills that are less equipped for eat­ing large fruits like olives dur­ing the winter.

Although, it is not known if those birds will end up as sep­a­rate species even­tu­ally, it goes with­out say­ing that it pro­vides input to the long-​standing debate about whether geo­graphic sep­a­ra­tion is nec­es­sary for spe­ci­a­tion to occur.

(Source: www​.sci​encedaily​.com)

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