Mating and reproductive success are influenced by traits that the transfer of gametes between potential mates. During this process deterministic processes subject to natural selection are important, but so are stochastic, non-deterministic processes. Mating success in plants can depend on plant and flower size but the movement of pollen by third-party vectors of pollination can result in mating events that are disassociated from heritable traits. We aimed to determine the extent to which patterns of mating and siring success could be explained by (potentially heritable) plant traits versus chance. We examined patterns of inter-plant mating distances, clonal intermingling and temporal variation in floral display size using field observations and parentage analysis using molecular markers in two populations with contrasting sexual systems (monoecy versus dioecy). The contributions to mating and reproductive success of plant traits versus chance were examined using multiple regression.
Results/Conclusions
Chance played a large role in mate acquisition in the dioecious population, with only 31% of the variation in mating success attributed to plant traits and the spatial and temporal patterns of flower production. However, in the monoecious population, only 15% of the variation in mating success was unexplained by the regression model. Our results provide a clear demonstration of how the deterministic processes that limit opportunities for natural and sexual selection in plant populations can vary across populations.
