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,
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.