Case studies and mathematical models of ecological speciation. 1. Cichlids in a crater lake.

Sergey Gavrilets, Aaron Vose, Marta Barluenga, Walter Salzburger, and Axel Meyer

Departments of  Ecology and Evolutionary Biology, Mathematics, and Computer Science, University of Tennessee, Knoxville, TN 37996 Department of Biology, University of Konstanz, D-78457 Konstanz, Germany. Department of Ecology and Evolution, University of Lausanne, UNIL Sorge, Le Biophore, CH-1015 Lausanne, Switzerland.

The study of a pair of sympatric species of cichlids in Lake Apoyo in Nicaragua published by Barluenga et al. (2006a) is viewed as providing probably one of the most convincing examples of sympatric speciation to date. Here, we describe and study a stochastic, individual-based, explicit-genetic model tailored for this cichlid system. Our results show that relatively rapid (< 20,000 generations) colonization of a new ecological niche and (sympatric or parapatric) speciation via local adaptation and divergence in habitat and mating preferences are theoretically plausible if (1) the number of loci underlying the traits controlling local adaptation and habitat and mating preferences is small, (2) the strength of selection for local adaptation is intermediate, (3) the carrying capacity of the population is intermediate, and (4) the effects of the loci influencing nonrandom mating are strong. We discuss patterns and time-scales of ecological speciation identified by our model. We highlight important parameters and features that need to be studied empirically to provide information that can be used to improve the biological realism and power of mathematical models of ecological speciation.