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Assortative mating and the genic view of speciation
Author(s) -
Bridle J. R.,
Ritchie M. G.
Publication year - 2001
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1046/j.1420-9101.2001.00344.x
Subject(s) - biology , assortative mating , evolutionary biology , reproductive isolation , epistasis , genetic algorithm , ecological speciation , mating , adaptation (eye) , ecological selection , character displacement , sympatric speciation , genetic divergence , disruptive selection , sexual selection , selection (genetic algorithm) , genetics , natural selection , sympatry , genetic diversity , genetic variation , population , gene flow , gene , demography , neuroscience , sociology , artificial intelligence , computer science
4 We welcome Wu's (2001) review of speciation from a genic perspective, and in particular its focus on the adaptive processes underlying the generation of new species, rather than the nature of the species themselves. However, we wish to stress that even from this perspec- tive, the evolution of assortative mating should continue to be seen as a process of special importance in speciation. Although adaptive divergence in mating behaviour or habitat preference is implicitly incorporated into a genic perspective, we believe that assortative mating should have particular emphasis because it can cause dramatic changes in the fitness landscape, as the behaviour of different genotypes rapidly generates many epistatic interactions that did not exist under conditions of random mating. Such selection on multilocus geno- types could rapidly create the holes in the fitness landscape envisaged by recent models of speciation (Gavrilets, 1999). These increased levels of epistasis will further increase the size of the genomic regions where linkage disequilibria can be maintained by selection, and where new epistatic alleles can spread to fixation, eventually contributing to post as well as further pre- mating isolation. However, in contrast to the generation of such post-mating incompatibilities, behavioural or signalling traits may evolve rapidly under direct selec- tion, in particular during adaptation to divergent habi- tats, under sexual selection, or under direct selection for increased assortment (reproductive character displace- ment or reinforcement). A key divergence in our viewpoint is illustrated by Wu's comments on transformed Drosophila lines 5 (p. 856). In our view, once behaviourally isolated these are indeed species because they are free to evolve independently, and to substitute different mutations at any part of the genome. This means they can diverge more quickly than genomes diverging under conditions of continued gene flow, where the substitution of such mutations is limited to regions where selection is strong relative to recombi- nation. By contrast, according to Wu's genic view, these hypothetical Drosophila lines are not species because they have not yet diverged at more than one (introduced) locus. In nature, however, there may be real examples of