Interações entre as espécies: poderosa força diretriz por detrás da evolução?

sexta-feira, fevereiro 26, 2010

Interactions Between Species: Powerful Driving Force Behind Evolution?

ScienceDaily (Feb. 25, 2010) — Scientists at the University of Liverpool have provided the first experimental evidence that shows that evolution is driven most powerfully by interactions between species, rather than adaptation to the environment.

Computer rendering of virus particles. In a new study, researchers used fast-evolving viruses to observe hundreds of generations of evolution. They found that for every viral strategy of attack, the bacteria would adapt to defend itself, which triggered an endless cycle of co-evolutionary change. (Credit: iStockphoto/Martin McCarthy)

The team observed viruses as they evolved over hundreds of generations to infect bacteria. They found that when the bacteria could evolve defences, the viruses evolved at a quicker rate and generated greater diversity, compared to situations where the bacteria were unable to adapt to the viral infection.

The study shows, for the first time, that the American evolutionary biologist Leigh Van Valen was correct in his 'Red Queen Hypothesis'. The theory, first put forward in the 1970s, was named after a passage in Lewis Carroll's Through the Looking Glass in which the Red Queen tells Alice, 'It takes all the running you can do to keep in the same place'. This suggested that species were in a constant race for survival and have to continue to evolve new ways of defending themselves throughout time.

Dr Steve Paterson, from the University's School of Biosciences, explains: "Historically, it was assumed that most evolution was driven by a need to adapt to the environment or habitat. The Red Queen Hypothesis challenged this by pointing out that actually most natural selection will arise from co-evolutionary interactions with other species, not from interactions with the environment.

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Nature advance online publication 24 February 2010 | doi:10.1038/nature08798; Received 8 September 2009; Accepted 23 December 2009; Published online 24 February 2010

Antagonistic coevolution accelerates molecular evolution

Steve Paterson1,5, Tom Vogwill1,5, Angus Buckling2, Rebecca Benmayor2, Andrew J. Spiers3, Nicholas R. Thomson4, Mike Quail4, Frances Smith4, Danielle Walker4, Ben Libberton1, Andrew Fenton1, Neil Hall1 & Michael A. Brockhurst1,5

1. School of Biological Sciences, Biosciences Building, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK

2. Zoology Department, University of Oxford, South Parks Road, Oxford OX1 3PS, UK

3. SIMBIOS Centre, Level 5 Kydd Building, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, UK

4. Pathogen Genomics, The Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK

5. These authors contributed equally to this work.

Correspondence to: Michael A. Brockhurst1,5 Correspondence and requests for materials should be addressed to M.A.B. (Email:


The Red Queen hypothesis proposes that coevolution of interacting species (such as hosts and parasites) should drive molecular evolution through continual natural selection for adaptation and counter-adaptation1, 2, 3. Although the divergence observed at some host-resistance4, 5, 6 and parasite-infectivity7,8, 9 genes is consistent with this, the long time periods typically required to study coevolution have so far prevented any direct empirical test. Here we show, using experimental populations of the bacterium Pseudomonas fluorescens SBW25 and its viral parasite, phage Φ2 (refs 10, 11), that the rate of molecular evolution in the phage was far higher when both bacterium and phage coevolved with each other than when phage evolved against a constant host genotype. Coevolution also resulted in far greater genetic divergence between replicate populations, which was correlated with the range of hosts that coevolved phage were able to infect. Consistent with this, the most rapidly evolving phage genes under coevolution were those involved in host infection. These results demonstrate, at both the genomic and phenotypic level, that antagonistic coevolution is a cause of rapid and divergent evolution, and is likely to be a major driver of evolutionary change within species.


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