On the Galapagos Islands, where Charles Darwin’s observations led to his evolutionary theory, scientists are now reporting that they’re witnessing a single species splitting into two, according to a new paper in the Proceedings of the National Academy of Sciences.
A husband and wife team, Peter and Rosemary Grant of Princeton University, have spent the past 36 years studying Darwin’s finches, technically know as tanagers. Darwin‘s observations of the birds during his voyage to the Galapagos on the HMS Beagle helped him arrive at the idea of evolutionary divergence: when different populations of a single species become geographically isolated, and evolve in different directions. The Grants have pushed that work further, with decades of painstaking observations providing a real-time record of evolution in action. In the PNAS paper, they describe something Darwin could only have dreamed of watching: the birth of a new species [Wired.com]. The process has been taking place with the help of a little bit of chance and a special song.
The split began in 1981 when an unusually large male finch from Santa Cruz island arrived on the island where the Grants were based, Daphne Major. The biologists tagged the bird number 5110, and followed him and his offspring through seven generations total. In the fourth generation a drought killed off all the descendants except one male and one female. These offspring became isolated because they have the avian equivalent of a strange accent. These finches learn their songs from their father, and the Grants suggest that 5110 sang the songs from his birth home of Santa Cruz then modified his come-hither ballad by roughly copying the Daphne Major birds’. This imperfect copying, they suggest, has over time acted as a barrier to interbreeding [Nature News]. So the immigrant bird’s descendants have bred only with each other for three generations.
The Grants say there’s no clear rule for when to declare a reproductively isolated population a new species, and also note that the birds descended from 5110 could still die out. But whatever happens, their legacy will remain: New species can emerge very quickly — and sometimes all it takes is a song [Wired.com].
The Grant’s are currently in Japan accepting the Kyoto Prize in basic science for their life’s work.
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Image: flickr / putneymark