Introduced deer and the pollination and reproduction of an animal-pollinated herb

Abstract

We evaluated the hypothesis that the modified population density of Aquilegia formosa Fisch. ex DC. (Ranunculaceae) resulting from the introduction of Sitka black-tailed deer ( Odocoileus hemionus sitkensis ) in the Haida Gwaii archipelago affects the pollination and reproductive performance of this herbaceous species. We compared the population density, pollination, and reproductive success of A. formosa among three small islands colonized by deer and three deer-free islands. Islands with deer had a substantially lower absolute density and a greater relative density of A. formosa than deer-free islands. The presence of deer was associated with higher pollen deposition, which probably resulted from the greater relative density of A. formosa on islands with deer. However, the presence of deer had no significant effect on individual reproductive success. The latter result is likely a consequence of the lack of pollen limitation in this species, as well as of the conflicting relationship between the absolute and relative densities of A. formosa and the presence of deer.