Human impacts altering Darwin's famous finches
Man-made changes to the environment of the Galapagos Islands, where Charles Darwin began to formulate his theory of evolution, are now affecting a famous embodiment of that theory, says a new study.
Darwin's finches are a classic example of adaptive radiation, having split from a single colonizing species into 14 different species having beak sizes and shapes best suited for feeding on different food types. Human activities appear to be blurring the distinctions among these alternative resources, thus increasing the survival of birds with intermediate beaks and causing diverging species to fuse back together.
The study, "Possible human impacts on adaptive radiation: beak size bimodality in Darwin's finches," set to be published May 3 in the online issue of the British journal Proceedings of the Royal Society B: Biological Sciences, was led by Andrew Hendry, a McGill professor in the Department of Biology and the Redpath Museum, and also involved a team of scientists from the UK, USA and Australia.
The researchers studied populations of finches within one species that show early signs of splitting into two species, perhaps providing a glimpse of how the entire adaptive radiation proceeded. The split the researchers documented was manifested as a division of the population into either small or large-beaked birds, with few intermediates.
But Professor Hendry's team found that when one of these populations came into contact with a rapidly expanding human population, the frequency of birds with intermediate beak sizes increased, thereby halting the apparent process of ongoing speciation.
Human activity has long been known to reduce biological diversity by precipitating extinctions. Research by Professor Hendry's team shows that humans may also slow or reverse the evolution of diversity.
For more information:
McGill University
Proceedings of the Royal Society of London B: Biological Sciences
