Variance in pollen carryover in animal-pollinated plants: Implications for mate choice

Abstract

We used analytical and simulation models to explore the effect of variance in pollen carryover on the diversity of donors contributing pollen to recipient flowers. The analytical model illustrated that as carryover rate drops, fewer donors can be sampled by any pollen recipient, and that this reduction in diversity is highly non-linear. Simulations of variable pollen carryover were carried out for two kinds of plant pollinator systems: (a) those in which little pollen on average is removed from a vector during a flower visit, and (b) those in which a large fraction of the available pollen is removed. In both cases, realized carryover is reduced as variance in carryover of pollen from one flower to the next increases. However, the reduction is disproportionately large in case (b). Introducing simulation results in the analytical projection of donor diversity suggests that in the extreme, variance in carryover can reduce the diversity of pollen “seen” by a flower by up to 70%. Thus, insofar as female choice is an adaptive process in flowering plants (and male fitness is enhanced by multiple opportunities for mating), natural selection should favor floral characters that stabilize pollen carryover rates.