Experimental analysis of mating patterns in a clonal plant reveals contrasting modes of self-pollination

Hermaphrodite plants commonly practice self-fertilization (selfing), but the mechanisms responsible vary depending on the mode of self-pollination, pollinator behavior, and degree of clonality. Whether selfing occurs within (autogamy) or between flowers (geitonogamy) is of evolutionary significance because their fitness consequences differ. We used floral manipulations and genetic markers to determine the relative contribution of autogamy and within- versus between-ramet geitonogamy to the selfing rate of the bumblebee-pollinated, clonal herb Aconitum kusnezoffii. Data on flowering phenology and bumblebee foraging were also collected to determine opportunities for different modes of self-pollination. Autogamy accounted for only 12% of the selfing rate with the remainder resulting from geitonogamy. Whole-ramet emasculation of clones with multiple ramets reduced selfing by 78%, indicating that within-ramet geitonogamy contributed significantly (68%) to total selfing. Selfing of single-ramet plants was 44% less than multiple-ramet plants, indicating that the contribution of between-ramet geitonogamy was substantially less (20%) than within-ramet geitonogamy, probably because of bumblebee foraging behavior. Our results demonstrate for the first time in a clonal plant that within-ramet geitonogamy is substantially greater than between-ramet geitonogamy and highlight the importance of considering the influence of clonal architecture and pollinator foraging on modes of self-pollination.