Evolution of Ovenbird Species Is Driven By Isolation, Not By Need To Differentiate

on December 22, 2013 1:02 PM EST

ovenbird
A study has found that it's not because of competition that birds' songs evolve differently, but because the birds evolve isolated from one another, subsequently meeting other birds of the same species millions of years later. (Photo: bmajoros, CC BY-SA 2.0)

The theory of evolution holds that species living together either evolve differently to avoid competition, or perish in the competitive struggle for survival. A new study, however, seems to challenge this thesis, finding that species of ovenbirds living together do not need to evolve differently in order to survive.

A team of Oxford University researchers analyzed the processes involved in causing the species-wide differences among ovenbirds. Although they found that species of ovenbirds living together were more different than those living apart, they claimed it was just a superficial observation. A closer examination that took into account variations in the age of different species revealed that co-existing species were more similar than species evolving separately. The findings, published in the journal Nature, appear to overturn the widespread Darwinian thesis.

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However, before actually debunking Darwin's theory, the researchers were cautious enough to generalize their claim. "'It's not so much a case of Darwin being wrong, as there is no shortage of evidence for competition driving divergent evolution in some very young lineages," study leader Dr. Joe Tobias, of Oxford University's Department of Zoology, said in a press release. "But we found no evidence that this process explains differences across a much larger sample of species"

This study appears to support the theory that speciation is more likely to occur when through geographic isolation, which leads to an emergence of differences - as originally propounded by Ernst Myers. The study team used genetic sequencing techniques to establish the age of different ovenbird lineages, and came to the conclusion that most ovenbird species evolved separately over millions of years in different geographical locations - such as Central America and South America - before they flocked together again.

The highly ambitious decade-long study looked at genetic sequences from 350 lineages of ovenbirds, in over 20 countries where their songs were recorded, and included over 90 percent of the ovenbird species. The researchers compared their beaks, legs, and songs. Their beaks and legs showed no comparable differences, regardless of whether they were living together or not. It surprised the researchers, however, that the birds' songs were remarkably alike when living together, which contradicts the long held view that bird species living together must evolve different songs to avoid confusion.   

Darwin's theory needs a fresh reinterpretation, because "'be different or die' doesn't appear to explain evolution," Dr. Tobias said in the press release. Competition doesn't exactly explain the species' differences, according to the researchers. The differences, "a wide variety of beaks, from long and hooked, to short and straight," seem to emerge when they live in isolation.

The evolution of similar songs challenges the dominant thesis held for so long, and it would require further studies to unfold this intriguing observation. The researchers, however, hypothesized that the development of similar songs benefits them against territorial incursions from rivals, whether from their species, or from other species co-existing, and competing for the same space and resources. 

This study distinguishes itself from the other studies by taking evolutionary age of species into account, according to Dr. Nathalie Seddon, co-author of the study. In the absence of this specific differentiator, this study appears to endorse Darwinian evolution. 

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