Pollination efficacy in the dioecious Coprosma spathulata was investigated in eight 900-m2 study plots. The mean fruit set was generally high ( 75% in six of eight populations), aided by male-biased populations, male floral abundance, and extended female receptivity in unpollinated flowers. However, pollen receipt and fruit set were both susceptible to reduction by dense understory vegetation, low abundance of males at the plot scale, and in isolated females. There was a steep reduction in fruit set when females were 7 from the nearest male, suggesting Allee effects in isolated females and in low-density populations. Although C. spathulata lives in an unpromising habitat for wind pollination, floral characteristics and flowering behavior ensure it is surprisingly successful.
