Shark Bait Blog

Environment.. and Scuba Diving.

Monday, December 07, 2009



Evolution.. and anthropogenic forcings

A study recently caught my attention that incorporated evolution, climate change and an anthropogenic forcing.. of particular interest was how rapidly this appeared to have occurred under suitable conditions.

'Researchers have discovered that the enthusiasm of many Britons for feeding birds in winter and the gradual warming of the British Isles due to climate change have helped change the appearance of the blackcap, a warbler as commonly recognized in European gardens as robins are in North America.

The differences have been modest, involving a slightly altered beak size and wing shape, according a paper on the finding published online in the journal Current Biology, but they've occurred in just a few decades, a pace that has stunned scientists.

“What's really catching people's attention with this paper is the speed at which evolution can manifest itself in short periods of time,” said Keith Hobson, a research scientist in Saskatoon with Environment Canada who helped with the study. Mr. Hobson said it was like seeing evolution “happening before our eyes.”

Scientists have been able to detect natural selection at work in the blackcaps because one population group of the birds began changing its annual migration route in the 1960s, appearing in Britain in significant numbers during the winter.

Until then, all blackcaps breeding in southern Germany and Austria each summer migrated south to the warmer Mediterranean areas of Spain to escape the central European winter.

The first blackcaps wintering in Britain were reported in 1959, and then with increasing frequency in later years, indicating the change in migratory route is a relatively new development.

The practice of putting suet and other rich foods in feeders and relatively warm winters in recent years allowed a British migratory population to evolve separately from its Spanish kin. Researchers believe the birds ended up in Britain, about 1,200 kilometres north of their regular winter grounds, because they flew off course from their usual migration routes.

If winters had been colder and bird feeders didn't exist, these wayward birds would have soon died due to starvation and inhospitable weather, but they thrived and now amount to about 10 per cent of the blackcap population.

“The British are very avid bird watchers and so I think we can be fairly certain … [the northward migration] only started in the 1960s,” said Martin Schaefer, a professor in the department of evolutionary biology at the University of Freiburg in Germany and lead researcher of the study.

The British blackcaps don't have as far to migrate to get back to southern Germany each summer, only about two-thirds of the distance of those that travel from Spain, so they arrive in the breeding grounds about 10 days earlier. This has created a condition known as reproductive isolation that is helping to maintain the different populations.

The birds have begun to look different because the British birds have evolved to have rounder wings better adapted for manoeuvrability and not as good for long-distance flying. They also have developed longer, thinner beaks because they no longer need an adaptation for eating large fruits, like olives, as they do in Spain.'
http://www.theglobeandmail.com/news/technology/science/british-birds-rapid-evolution-signals-human-impact/article1387804/


(photo courtesy of Jakub Stančo)

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