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STRONG ASSORTATIVE MATING BY DIET, COLOR, SIZE, AND MORPHOLOGY BUT LIMITED PROGRESS TOWARD SYMPATRIC SPECIATION IN A CLASSIC EXAMPLE: CAMEROON CRATER LAKE CICHLIDS
Author(s) -
Martin Christopher H.
Publication year - 2013
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/evo.12090
Subject(s) - sympatric speciation , assortative mating , disruptive selection , biology , ecological speciation , cichlid , genetic algorithm , sympatry , adaptive radiation , allopatric speciation , evolutionary biology , pelagic zone , incipient speciation , mating preferences , sexual selection , ecology , mating , selection (genetic algorithm) , natural selection , mate choice , fishery , gene flow , phylogenetics , fish <actinopterygii> , genetic variation , population , artificial intelligence , sociology , computer science , biochemistry , demography , gene
Models predict that sympatric speciation depends on restrictive parameter ranges, such as sufficiently strong disruptive selection and assortative mating, but compelling examples in nature have rarely been used to test these predictions. I measured the strength of assortative mating within a species complex of Tilapia in Lake Ejagham, Cameroon, a celebrated example of incipient sympatric adaptive radiation. This species complex is in the earliest stages of speciation: morphological and ecological divergence are incomplete, species differ primarily in breeding coloration, and introgression is common. I captured 27 mated pairs in situ and measured the diet, color, size, and morphology of each individual. I found strong assortative mating by color, size, head depth, and dietary source of benthic or pelagic prey along two independent dimensions of assortment. Thus, Ejagham Tilapia showed strong assortative mating most conducive to sympatric speciation. Nonetheless, in contrast to a morphologically bimodal Sarotherodon cichlid species pair in the lake, Ejagham Tilapia show more limited progress toward speciation, likely due to insufficient strength of disruptive selection on morphology estimated in a previous study (γ = 0.16). This supports the predicted dependence of sympatric speciation on strong assortment and strong disruptive selection by examining a potentially stalled example in nature.