Recent empirical evidence suggests that individuals use genetic compatibility (or genetic dissimilarity) as a criterion when choosing mates. Heterozygote offspring should have a fitness advantage compared with homozygotes and therefore females choose the m ales that share the fewest alleles across loci with the female - the genetically compatible males. We propose to study the effect of genetic incompatibility on fitness and female choice for genetic compatible males in selection experiments using the beetle Callasobruchus maculatus. We will create different homozygote genotypes through selection of replicated female isolines and test the different genotypes for incompatibility on standard nuclear genetic backgrounds. Females will be given the possibility to mate with males of different compatibility relative to their own genotype in choice experiments. Pre- and post mating female choice will be examined through paternity analyses and fitness will be determined in bioassays. Understanding the role of choice for genetic dissimilarity is a major challenge to the prevailing concepts of mate choice and sexual selection.
The criterion of choice for genetic dissimilarity is based on the relative difference between particular genomes rather than an absolute quality criterion such as heterozygosity per se or a fixed trait, such as a condition-dependent male signal. We will establish whether females make use of both absolute and relative criteria and will strive to resolve the apparent paradox that is inherent in simultaneous mate choice of these two types of male traits. Preliminary studies of this system have shown that both types of male traits are important in mate choice. By using standard fitness assays, we will for the first time be able to relate the mate choices females make with the fitness consequences of these choices. This research will be fundamental for understanding evolutionary processes of reproductive isolation, genetic divergence and parapatric speciation.
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