POLLINATION, CAPSULE DAMAGE, AND THE PRODUCTION OF SEEDS IN SALIX SETCHELLIANA (SALICACEAE), AN ALASKAN GLACIAL RIVER GRAVEL BAR WILLOW

Salix setchelliana, a clonal prostrate willow. is a dominant species o f glacial river gravel bars in Denali National Park, Alaska. This habi tat, which is located between migrating river channels, is unpredictab le in time, patchy in space, and essentially alpine in nature. The spe cies takes advantage of both entomophily and anemophily, thus perhaps improving its success under these conditions. It is dependent primaril y on insect pollination, carried out by a variety of species, but wind pollination accounted for 7-25% of seed production. The number of see ds per capsule was much below the potential maximum. Seed predation, a nd probably insufficient pollination, influenced seed production. Pred ation accounted Tar a 70% reduction in seed production per capsule in an open pollination treatment (P = 0.005). There were significant diff erences in number of seeds per capsule between collection sites (P = 0 .0022). An inverse relationship was observed between seed predation le vels and seed numbers in both insect-damaged and undamaged capsules.