EVOLUTION OF FEMALE CHOICE IN SEAWEED FLIES - FISHERIAN AND GOOD GENES MECHANISMS OPERATE IN DIFFERENT POPULATIONS

The relative contributions of the Fisher process and viability indicator mechanisms to the maintenance of a female mating preference in seaweed flies have been assessed. Both types of mechanism seem to operate, but their effectiveness varies in different populations depending on ecological factors. In stable populations not subject to tidal variation, all females prefer to mate with large males and produce large, 'sexy' sons. In contrast, females from a tidal population, which suffers regular genetic bottlenecks, appear to mate disassortatively with respect to both size and a chromosomal inversion system, thereby increasing the proportion of highly fit, heterokaryotypic offspring. This relation between population stability and female preference suggests that the Fisher process may not operate in populations suffering genetic bottlenecks.