The influence of deer browsing on the reproductive biology of Canada yew (Taxus canadensis marsh.) : II. Pollen limitation: an indirect effect.

Hand-pollination significantly increased seed production in a Canada yew (Taxus canadensis) population that had been browsed previously by white-tailed deer (Odocoileus virginianus) indicating that pollen availability limited seed production in this population. Handpollination did not significantly increase seed production in a population never browsed by deer. Deer-browsing significantly reduces yew density and pollen production, which in turn results in reduced pollination and seed production. Pollen limitation of yew seed production is an indirect effect of deer browsing on Canada yew and results from an interaction between the direct effect of deer browsing and the pollination syndrome of Canada yew. Artificially created female yews had lower seed set than monoecious yews when yew seed production was pollen-limited, but not when pollen did not limit seed production.