Evolutionary branching under slow directional evolution

Ito HC & Dieckmann U (2014). Evolutionary branching under slow directional evolution. Journal of Theoretical Biology: 290-314. DOI:10.1016/j.jtbi.2013.08.028.

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Evolutionary branching is the process by which ecological interactions induce evolutionary diversification. In asexual populations with sufficiently rare mutations, evolutionary branching occurs through trait-substitution sequences caused by the sequential invasion of successful mutants. A necessary and sufficient condition for evolutionary branching of univariate traits is the existence of a convergence stable trait value at which selection is locally disruptive. Real populations, however, undergo simultaneous evolution in multiple traits. Here we extend conditions for evolutionary branching to bivariate trait spaces in which the response to disruptive selection on one trait can be suppressed by directional selection on another trait. To obtain analytical results, we study trait-substitution sequences formed by invasions that possess maximum likelihood. By deriving a sufficient condition for evolutionary branching of bivariate traits along such maximum-likelihood-invasion paths (MLIPs), we demonstrate the existence of a threshold ratio specifying how much disruptive selection in one trait direction is needed to overcome the obstruction of evolutionary branching caused by directional selection in the other trait direction. Generalizing this finding, we show that evolutionary branching of bivariate traits can occur along evolutionary-branching lines on which residual directional selection is sufficiently weak. We then present numerical analyses showing that our generalized condition for evolutionary branching is a good indicator of branching likelihood even when trait-substitution sequences do not follow MLIPs and when mutations are not rare. Finally, we extend the derived conditions for evolutionary branching to multivariate trait spaces.

Item Type: Article
Uncontrolled Keywords: Frequency-dependent selection; Speciation; Adaptive dynamics; Two-dimensional traits; Multi-dimensional traits
Research Programs: Evolution and Ecology (EEP)
Bibliographic Reference: Journal of Theoretical Biology; 360:290-314 (7 November 2014) (Published online 5 September 2013)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:50
Last Modified: 24 Feb 2016 15:15
URI: http://pure.iiasa.ac.at/10857

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