The difference in the colour morphs is genetically controlled and of interest as a striking example of rapid evolutionary change in a localized area.
The difference between the morphs in B. betularia could also be considered as variation in pattern rather than melanisation per se because the typical form has black patches, which define an underlying pattern, whereas carbonaria is completely black, except for two small white spots where the forewing attaches to the thorax.
The absence of a difference in osmotic pressures between bulgy morph and control tadpoles, despite the significant difference in the total volume of body fluids, suggests the likelihood of differences in ion concentrations between the phenotypes (Fig. 5).
In the current system, NFDS alone is not sufficient to form the cline in morph frequency and the geographic morph cline cannot be expected without the underlying potential fitness difference between the morphs.
Based on sexual conflict theory, we expected to find differences between the morphs in the number of matings received, their ability to reject male mating attempts and the fecundity-consequences of both mating attempts and realized matings.
Studies of polymorphic Plethodon cinereus have shown differences between the morphs in behaviour [ 11, 14, 15, 19], physiology [ 11, 13], and geographic variation in relative abundance [ 10, 20].
The larger the difference in fitness potential between morphs becomes, the more the equilibrium of morph frequency biases.
Thus, the differences in throat color morph frequencies between the geographically close islet populations with similar habitats (Figs. 2A-B) could potentially partly be a result of stochastic processes.
Population was treated as a fixed factor rather than a random factor because we are interested in examining the differences in morph frequencies among our specific populations, and the same populations would be analysed in future studies (Bennington and Thayne 1994; Potvin 2001).
The differences in general colour morph in model 3 are explained by the differences between males and females alone.
