London, Dec 4 (Inditop.com) Birds can tweak their evolution with the seemingly innocent pastime of feeding, says a new study.
For instance, this feeding habit became instrumental in splitting a single population of blackcaps into two reproductively isolated groups in less than 30 generations, even though they continue to breed side by side in the very same forests.
The reproductive isolation between these populations, which live together for part of the year, is now stronger than that of other blackcaps that are always separated from one another by distances of 800 km or more, the study said.
The split that the researchers observed followed the recent establishment of a migratory divide between southwest- and northwest-migrating blackcap (Sylvia atricapilla) 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 Britain — and faced distinct selective pressures. Under that pressure, the two groups have since become locally adapted ecotypes.
Ecotypes represent the initial step of differentiation among populations of the same species, the researchers explained. If ecotypes continue down that path, they can ultimately become separate species.
“It shows that we are influencing the fate not only of rare and endangered species, but also of the common ones that surround our daily lives,” said Martin Schaefer of the University of Freiburg (U-F) in Germany.
“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,” Schaefer said.
“As a consequence, birds migrating northwest have rounder wings, which provide better manoeuvrability 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.
“This is a nice example of the speed of evolution,” he added. “It is something that we can see with our own eyes if we only look closely enough. It doesn’t have to take millions of years,” said Schaefer.
These findings were published online in Current Biology.
