The evolution of colour patterns in the western rainbowfish, Melanotaenia australis

[Truncated abstract] When the relative strengths of sexual selection and natural selection by predators differ among populations of a species, their interaction is thought to result in phenotypic variation across the range of that species. Where predation intensity is low and sexual selection is the more powerful agent of selection, total selection is expected to favour conspicuous male phenotypes. Where predation intensity is high, conspicuousness can be a liability despite its advantages under sexual selection, and total selection may therefore favour cryptic male phenotypes. My thesis tests this model using the western rainbowfish Melanotaenia australis, a freshwater fish endemic to north-western
Australia which exhibits striking variation in male phenotype across populations. I
hypothesized that in this species, variation in male phenotype is associated with
variation in predation regime, variation in male phenotype represents adaptive genetic divergence among populations, and male phenotype is under sexual selection.