Evolution while you wait

Well, only if you’re not the foot-tapping type.  Those crazy, evolutionary-thought provoking finches are at it again.  Peter and Rosemary Grant, evolutionary biologists at Princeton, authored a study recently published in the Proceedings of the National Academy of Sciences that provides a view into evolution that no one’s really ever had before.  The researchers used Darwin’s finches–thus named for their profound influence on Charles Darwin– as a model system and tracked the descendants of an immigrant finch for 28 years on the Galapagos Island of Daphne Major.

Wikipedia Commons, John Gould

The newcomer, a  large, male Geospiza fortis, had very likely come from the nearby island of Santa Cruz, as determined by genetics.  This particular bird, dubbed 5110 (maybe if they named him Fred, they would’ve gotten attached) , had a slightly different beak and sang a slightly different song than the local Geospiza fortis population. The Grants followed this individual’s offspring, which also sported beaks and songs that resembled their parents’ more than the other finches, for almost the next three decades.  In a later generation, a drought occurred on the island and all but one mating pair (a brother and a sister) perished.  In the generations since, their descendants only began to breed within their population, reproductively isolating themselves.

So why the isolation?  Why no breeding across populations?  Likely, this has to do with the music, according to the Grants.   Finches’ songs aren’t genetically passed down–no finch instinctively sings one song or the other.  They learn songs from their parents.  When 5110 originally came to town, he attempted to copy the local’s songs, but this wasn’t a perfect conversion.  If you’re an I Love Lucy fan, think of Ricky Ricardo slowly developing a New York accent.  He still smugly sings Baba Lu like no native New Yorker.  5110’s kids (and their kids and so on) developed their dad’s song style; and along with ecological factors related to their new beak morphology, this musical difference is perhaps what led to the reproductive isolation.

Isolation of a population via a barrier to interbreeding can lead to speciation, which is  essentially how new species come about–thus, this could be the first step in 5110’s lineage evolving into a new species.   Evolution in action!  Now if only we could figure out when a divergent population becomes a new species… Or what exactly a species should be defined as (the species problem)…

ResearchBlogging.org

Grant, P., & Grant, B. (2009). Inaugural Article: The secondary contact phase of allopatric speciation in Darwin’s finches Proceedings of the National Academy of Sciences, 106 (48), 20141-20148 DOI: 10.1073/pnas.0911761106

(You probably won’t be able to view the article unless you have a PNAS subscription.  But you can snag the abstract here.)

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