title: The one-third law of evolutionary dynamics.
abstract: Evolutionary game dynamics in finite populations provide a new framework for studying selection of traits with frequency-dependent fitness. Recently, a "one-third law" of evolutionary dynamics has been described, which states that strategy A fixates in a B-population with selective advantage if the fitness of A is greater than that of B when A has a frequency 13. This relationship holds for all evolutionary processes examined so far, from the Moran process to games on graphs. However, the origin of the "number"13 is not understood. In this paper we provide an intuitive explanation by studying the underlying stochastic processes. We find that in one invasion attempt, an individual interacts on average with B-players twice as often as with A-players, which yields the one-third law. We also show that the one-third law implies that the average Malthusian fitness of A is positive.
authors.affiliation: Program for Evolutionary Dynamics, Harvard University, Cambridge, MA 02138, USA. ohtsuki@fas.harvard.edu
authors.forename: Hisashi
authors.initials: H
authors.lastname: Ohtsuki
authors.forename: Pedro
authors.initials: P
authors.lastname: Bordalo
authors.forename: Martin A
authors.initials: MA
authors.lastname: Nowak
mesh_terms: D000818:Animals; D005075:Biological Evolution; D005716:Game Theory; D008957:Models, Genetic; D011156:Population Density; D011157:Population Dynamics; D012641:Selection, Genetic; D013269:Stochastic Processes