“First Arrival” Hypothesis in Darwin’s Finches Gets Some Caveats

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“First Arrival” Hypothesis in Darwin’s Finches Gets Some Caveats






By
John Toon | April 26, 2017
• Atlanta, GA








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Georgia Tech Ph.D. student Xian Yang takes a sample of water from Lake Clara Meer in Atlanta’s Piedmont Park. Bacteria from the lake were among those studied as competitors to Pseudomonas fluorescens SBW-25 in the study of adaptive radiation. (Credit: Qianna Xu, Georgia Tech)





Being first in a new ecosystem provides major advantages for pioneering species, but the benefits may depend on just how competitive later-arriving species are. That is among the conclusions in a new study testing the importance of “first arrival” in controlling adaptive radiation of species, a hypothesis famously proposed for “Darwin’s Finches,” birds from the Galapagos Islands that were first brought to scientific attention by the famous naturalist.

Researchers at the Georgia Institute of Technology tested the importance of first arrival with bacterial species competing in a test tube. Using a bacterium that grows on plant leaves, they confirmed the importance of first arrival for promoting species diversification, and extended that hypothesis with some important caveats.

“We wanted to understand the role of species colonization history in regulating the interaction between the rapidly-evolving bacterium Pseudomonas fluorescens SBW-25 and competing species and how that affected P. fluorescens adaptive radiation in the ecosystem,” said Jiaqi Tan, a research scientist in Georgia Tech’s School of Biological Sciences. “The general pattern we find is that the earlier arrival of P. fluorescens allowed it to diversify to a greater extent. If the competing and diversifying species are very similar ecologically, we find a stronger effect of species colonization history on adaptive radiation.”

The research is reported April 26th in the journal Evolution and was supported by the National Science Foundation. The study is believed to be the first rigorous experimental test of the role ...

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