Cushion plants in the alpine of British Columbia, Canada: Systematic review, trophic facilitation, and pollen limitation

The overarching hypothesis tested is that cushion plants are foundation species in the alpine, contributing to ecosystem structure and function. This thesis provides a systematic review of cushion plant ecology literature, then quantifies the effect of cushions on higher trophic levels, and finally assesses pollen limitation with a manipulative experiment. The majority of cushion species in many locations have never been studied. Community level trophic effects of cushions are unknown. From extensive observations, cushions have a significant positive effect on community diversity of arthropods and pollinators. No evidence of pollen limitation and low rates of selfing, indicate that pollination rates are high. Hence, cushions are foundation species or module hubs in the ecological network and pollinators, critical for the reproduction of alpine plants. The loss of either cushions or pollinators in the alpine would therefore have significant community wide implications to the structure and function of the ecosystem.