An Analytically Tractable Model for Competitive Speciation

Pennings, P.S., Kopp, M., Meszena, G., Dieckmann, U. ORCID: https://orcid.org/0000-0001-7089-0393, & Hermisson, J. (2008). An Analytically Tractable Model for Competitive Speciation. IIASA Interim Report. IIASA, Laxenburg, Austria: IR-08-046

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Abstract

Several recent models have shown that frequency-dependent disruptive selection created by intraspecific competition can lead to the evolution of assortative mating 4 and, thus, to competitive sympatric speciation. However, since most results from these 5 models rely on limited numerical analyses, their generality has been subject to considerable debate. Here, we consider one of the standard models, the so-called Roughgarden model, with a simplified genetics where the selected trait is determined by a single diallelic locus. This model is sufficiently complex to maintain key properties of the general multilocus case, but still simple enough to allow for a comprehensive analytical treatment. By means of invasion fitness analysis, we describe the impact of all model parameters on the evolution of assortative mating. Depending on (1) the strength and (2) shape of stabilizing selection, (3) the strength and (4) shape of pairwise competition, (5) the shape of the mating function, and (6) the type of assortative mating, which may or may not lead to sexual selection, we find five different evolutionary regimes. In one of these regimes, the evolution of complete reproductive isolation is possible through arbitrarily small steps in the strength of assortative mating. Our approach provides a mechanistic understanding of several phenomena that have been found in previous models. The results demonstrate how, even in a simple model of competitive speciation, results depend in a complex way on ecological and genetic parameters.

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