Wind pollination was experimentally demonstrated in Linanthus parviflorus (Polemoniaceae), a predominantly beeflypollinated, self-incompatible annual. Seed set in plants enclosed in mesh tents that excluded pollinators but allowed airborne pollen flow provided evidence for wind pollination, and the extent of seed set due to wind pollination was compared to that in open-pollinated controls and pollen-supplemented treatments. Additional controls were included to test for possible confounding effec
ts of the mesh tent. Mean seed number in open-pollinated plants was 72.8–81.1% of that in pollensupplemented plants, while wind pollination alone produced 49.5–52.2%, a smaller but substantial proportion of seed set with pollen supplementation. Further evidence for wind pollination was found in a comparison of sites differing in the extent of wind exposure in two populations of L. parviflorus. Airborne pollen counts were higher in exposed sites than in protected sites, and the difference was marginally significant. Seed set was significantly pollen limited in protected sites, but not in exposed sites. Taken together, the data suggest that wind pollination provides some reproductive assurance in this obligately outcrossing species. Wind pollination is hypothesized to represent an alternative to selfing as an evolutionary solution to the problem of temporal or spatial variation in pollination visitation.
Reduced allocation to structures for pollinator attraction is predicted in selfing species. We explored the association between outcrossing and floral display in a broad sample of angiosperms. We used the demonstrated relationship to test for bias against selfing species in the outcrossing rate distribution, the shape of which has relevance for the stability of mixed mating. Relationships between outcrossing rate, flower size, flower number and floral display, measured as the product of flower s
ize and number, were examined using phylogenetically independent contrasts. The distribution of floral displays among species in the outcrossing rate database was compared with that of a random sample of the same flora. The outcrossing rate was positively associated with the product of flower size and number; individually, components of display were less strongly related to outcrossing. Compared with a random sample, species in the outcrossing rate database showed a deficit of small floral display sizes. We found broad support for reduced allocation to attraction in selfing species. We suggest that covariation between mating systems and total allocation to attraction can explain the deviation from expected trade-offs between flower size and number. Our results suggest a bias against estimating outcrossing rates in the lower half of the distribution, but not specifically against highly selfing species.