THE EVOLUTION OF INDICATOR TRAITS FOR PARENTAL QUALITY - THE ROLE OF MATERNAL AND PATERNAL EFFECTS

In systems where individuals provide material resources to their mates or offspring, mate choice based on traits that are phenotypically cor related with the quality of resources provided is expected to be adapt ive. Several models have explored the evolution of mating preference w here there are direct benefits to choice, but few have addressed how a phenotypic correlation can be established between a male indicator tr ait and the degree of parental investment. We present a model with thr ee quantitative traits: male and female parental investment and a pote ntial male indicator trait. In our model, the expression of the ''indi cator'' trail in offspring is affected by parental investment. These e ffects are referred to as maternal or paternal effects, or as ''indire ct genetic effects'' when parental investment is heritable. With genet ic variation for degree of parental investment, offspring harbor genes for parental investment that an unexpressed before mating but will af fect the investment that they provide when expressed. Because the in v estment received from the parents affects the expression of the indica tor trait, there will be a correlation between the genes fur parental investment inherited and the degree of expression of the indicator tra il in the offspring. The indicator trait is thus an ''honest'' signal for the degree of paternal investment.