Assortative Mating and Plant Phenology: Evolutionary and Practical Consequences

Abstract

Variation in mating phenology causes assortative mating for phenological traits. Here I show that this assortative mating can be strong, as it is caused not only by periods of non-overlap in flowering, but also by variation in the composition of the mating pool during periods of overlap. Using a one-locus, two-allele model, I show that this temporal assortative mating can: (1) lead to declines in mean fitness under balancing selection, including fixation of one allele; (2) strongly affect the rate of response to directional selection; and (3) determine the boundaries of the basins of attraction under disruptive selection. These results suggest that the evolution of phenological traits – and traits functionally coupled with them – may be more complex than we have generally thought. They also suggest caution in interpreting the results of studies (e.g. quantitative genetic studies) that assume randomly mating populations.