Evolution: Not Only the Fittest Survive
ScienceDaily (Mar. 27, 2011) — Darwin's notion that only the fittest survive has been called into question by new research published in the journal Nature. A collaboration between the Universities of Exeter and Bath in the UK, with a group from San Diego State University in the US, challenges our current understanding of evolution by showing that biodiversity may evolve where previously thought impossible.
Bacteria growing on a Petri plate. (Credit: iStockphoto/Monika Wisniewska)
The work represents a new approach to studying evolution that may eventually lead to a better understanding of the diversity of bacteria that cause human diseases.
Conventional wisdom has it that for any given niche there should be a best species, the fittest, that will eventually dominate to exclude all others.
This is the principle of survival of the fittest. Ecologists often call this idea the `competitive exclusion principle' and it predicts that complex environments are needed to support complex, diverse populations.
Professor Robert Beardmore, from the University of Exeter, said: "Microbiologists have tested this principle by constructing very simple environments in the lab to see what happens after hundreds of generations of bacterial evolution, about 3,000 years in human terms. It had been believed that the genome of only the fittest bacteria would be left, but that wasn't their finding. The experiments generated lots of unexpected genetic diversity."
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Metabolic trade-offs and the maintenance of the fittest and the flattest
Robert E. Beardmore, Ivana Gudelj, David A. Lipson, & Laurence D. Hurst
AffiliationsContributionsCorresponding author
Nature (2011) doi:10.1038/nature09905Received 01 December 2010 Accepted 07 February 2011 Published online 27 March 2011
How is diversity maintained? Environmental heterogeneity is considered to be important1, yet diversity in seemingly homogeneous environments is nonetheless observed2. This, it is assumed, must either be owing to weak selection, mutational input or a fitness advantage to genotypes when rare1. Here we demonstrate the possibility of a new general mechanism of stable diversity maintenance, one that stems from metabolic and physiological trade-offs3. The model requires that such trade-offs translate into a fitness landscape in which the most fit has unfit near-mutational neighbours, and a lower fitness peak also exists that is more mutationally robust. The ‘survival of the fittest’ applies at low mutation rates, giving way to ‘survival of the flattest’4, 5, 6 at high mutation rates. However, as a consequence of quasispecies-level negative frequency-dependent selection and differences in mutational robustness we observe a transition zone in which both fittest and flattest coexist. Although diversity maintenance is possible for simple organisms in simple environments, the more trade-offs there are, the wider the maintenance zone becomes. The principle may be applied to lineages within a species or species within a community, potentially explaining why competitive exclusion need not be observed in homogeneous environments. This principle predicts the enigmatic richness of metabolic strategies in clonal bacteria7 and questions the safety of lethal mutagenesis8, 9 as an antimicrobial treatment.
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NOTA CAUSTICANTE DESTE BLOGGER:
Gente, nós estamos falando de bactérias, e os menos aptos sobrevivem e evoluem, contrariando a hipótese de Darwin de que somente os mais aptos são os que sobrevivem. Mas isso é pura tautologia, e tautologia não é ciência, é pensamento circular.
As bactérias dão dor de cabeça a Darwin não é de hoje. Vide o flagelo bacteriano que os processos evolucionários gradualistas darwinianos não explicam.
Darwin, cara, nem bactéria??? O que dizer então de formas biológicas 'superiores'???
