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 indicat or mechanisms to the maintenance of a female mating preference in seaw eed 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 variati on, all females prefer to mate with large males and produce large, 'se xy' sons. In contrast, females from a tidal population, which suffers regular genetic bottlenecks, appear to mate disassortatively with resp ect to both size and a chromosomal inversion system, thereby increasin g the proportion of highly fit, heterokaryotypic offspring. This relat ion between population stability and female preference suggests that t he Fisher process may not operate in populations suffering genetic bot tlenecks.