Despite Extensive Pollinator Sharing, Invasive Blackberry has Negligible Impacts on Reproductive Success of a Rare Native Wildflower

Abstract

Abstract Plant invasions have the potential to disrupt community dynamics and impair essential ecosystem services, including the pollination of native flowers. Invaders most likely to invoke pollinator competition are characterized by conspicuous, resource-rich blooms and long flowering periods, while the natives most likely to be impacted are obligate out-crossers that are sensitive to disturbance or locally rare. We investigated the effects of a widespread showy invader of the Pacific Northwest, Rubus armeniacus (Himalayan blackberry), on an imperiled endemic wildflower, Sidalcea hendersonii. We observed pollinators, quantified pollen deposition and conducted pollen-supplementation experiments on S. hendersonii plants growing at three distances (1 m, 15 m and 50 m) from well-established blackberry patches in five adjacent field plots. Individual R. armeniacus flowers received more than three times as many total visits as S. hendersonii inflorescences; however, there was minimal overlap between the polli...