Posted by: Dan | November 19, 2009

Birth of a New Species

It’s pretty rare that biologists find an instance where speciation appears to have occurred right in front of their very eyes, but it appears that Peter and Rosemary Grant have looked closely enough over the course of a few decades to have seen it. As Allen writes on The EvolutionList, A New Species of Finch may have Evolved in the Galapagos:

Peter and Rosemary Grant have been studying the finches of Daphne Major, a small island in the Galapagos archipelago since 1973. In PNAS, they have proposed that a population of finches on Daphne Major may be on the verge of becoming a new species of finch. Here’s how their proposal was reported at Nature.com News:

“It was in 1981, that the Grants spotted an unusually heavy medium ground-finch (Geospiza fortis). At 29.7 grams, the male was more than 5 grams heavier than any they had seen on Daphne Major before. Genetic analysis showed that it probably came from the neighbouring island of Santa Cruz.

The Grants numbered the bird 5110 and followed it and all its known descendants over seven generations. Many of its descendants stuck out from the other G. fortis on Daphne Major: they had unusually shaped beaks and their songs differed from those of the other finches.

In the fourth generation, a severe drought hit the island and 5110’s descendants were reduced to one male and one female — a brother and sister. From then on the immigrant lineage isolated itself, breeding with no other G. fortis on the island….

Go check out the rest of Allen’s post for his analysis, and check out the article in PNAS as well. The Grants present the take-home message there in the final part of the abstract: “The study reveals additional stochastic elements of speciation, in which divergence is initiated in allopatry; immigration to a new area of a single male hybrid and initial breeding with a rare hybrid female.”


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