American Journal of Botany 93(2): 226–233. 2006. EFFECT OF FLOWERING PHENOLOGY ON POLLEN FLOW DISTANCE AND THE CONSEQUENCES FOR SPATIAL GENETIC STRUCTURE WITHIN A POPULATION OF

To evaluate the effects of flowering phenology on pollen flow distance and spatial genetic structure in a population of a bumblebee-pollinated herb, Primula sieboldii, we investigated the flowering phenology of 1712 flowers of 97 genets in a population in Nagano Prefecture, Japan, and constructed a mating model based on the observed mating pattern, which was revealed by paternity analysis using 11 microsatellite markers. The effects of flowering phenology were inferred by comparing estimated pollen flow distance and the level of heterozygosity in the next generation between two scenarios. In the first scenario, both the intergenet distance and flowering phenology influenced mating opportunity, while in the second scenario only intergenet distance influenced mating opportunity. Although the frequency distribution of pollen flow distance at the population level did not differ significantly between the two scenarios, the mean pollen flow distance of several flowers increased by more than 10 m as a result of variation in flowering phenology. Furthermore, accounting for flowering phenology predicted change in heterozygosity in the next generation from 20.04 to 0.07. The results showed that flowering phenology can affect pollen flow distance and spatial genetic structure. Key words: bumblebee; flowering time; heterostyly; mating model; microsatellite; Nagano Prefecture; paternity analysis; Pri-mulaceae. Knowledge of effective pollen flow distance has great im-portance in evolutionary and conservation genetics, because pollen flow distance can strongly affect spatial genetic struc