Seed Dormancy and Frequency Dependent Selection Due to Sib Competition: the Effect of Age Specific Gene Expression

We analyse the evolution of postponed seed germination in temporally and spatially homogenous habitats under the assumption that sibling seedlings compete because of clumped seed dispersal. The seed germination trait is assumed to be affected by two sets of autosomal genes. One set controls a germination factor that is expressed in young individuals, i.e. this factor determines the embryoʹs propensity to delay germination. The other set of genes controls a germination factor that is expressed in the seed coat, which, because this is maternal tissue, represents an adult trait. o germination factors together determine the probability of a seed germinating as a function of time. The corresponding probability density function of germination times represents a seedʹs germination strategy. We investigate the evolutionary stability of such strategies by introducing rare mutant modifier alleles that give rise to small deviations with respect to germination strategies. alysis shows that the coevolution of the two sets of genes leads to a joint ESS which is such that the embryonal trait favours a faster germination regime than does the adult one. We suggest that this joint ESS is best seen as a result of conflicting selection pressures acting upon genes with age-specific expression, rather than as a conflict between parents and their offspring.