O fluxo de aptidão e a ubiquidade da evolução adaptativa

quarta-feira, fevereiro 10, 2010

Fitness flux and ubiquity of adaptive evolution

Ville Mustonen1 and Michael Lässig2

-Author Affiliations

Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany

↵1Present address: Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, United Kingdom.

Edited by Curtis G. Callan, Princeton University, Princeton, NJ, and approved December 14, 2009 (received for review July 26, 2009)

Abstract

Natural selection favors fitter variants in a population, but actual evolutionary processes may decrease fitness by mutations and genetic drift. How is the stochastic evolution of molecular biological systems shaped by natural selection? Here, we derive a theorem on the fitness flux in a population, defined as the selective effect of its genotype frequency changes. The fitness-flux theorem generalizes Fisher’s fundamental theorem of natural selection to evolutionary processes including mutations, genetic drift, and time-dependent selection. It shows that a generic state of populations is adaptive evolution: there is a positive fitness flux resulting from a surplus of beneficial over deleterious changes. In particular, stationary nonequilibrium evolution processes are predicted to be adaptive. Under specific nonstationary conditions, notably during a decrease in population size, the average fitness flux can become negative. We show that these predictions are in accordance with experiments in bacteria and bacteriophages and with genomic data in Drosophila. Our analysis establishes fitness flux as a universal measure of adaptation in molecular evolution.

adaptive evolution    fitness landscapes    fluctuation theorems in statistical physics 

fundamental theorem of natural selection

Footnotes

2To whom correspondence should be addressed. E-mail: lassig@thp.uni-koeln.de.

Author contributions: V.M. and M.L. designed research, performed research, analyzed data, and wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/cgi/content/full/0907953107/DCSupplemental.

+++++

PDF gratuito do artigo aqui.