Functions of staminate flowers in andromonoecious Pseudocymopterus montanus (Apiaceae, Apioideae)

The pollen donor and pollinator attractor hypotheses are non‐exclusive alternative explanations for the functions of the staminate flowers of andromonoecious plants. We tested assumptions and predictions of both hypotheses using the andromonoecious perennial Pseudocymopterus montanus (Apiaceae, Apioideae), in which staminate flowers are approximately one‐third as massive as perfect ones and sequentially blooming umbels bear varying proportions of staminate flowers. We confirmed that larger umbels receive more visits than smaller ones. We demonstrated that fluorescent dye is a suitable analog of P. montanus pollen and that larger umbels donate more dye to nearby recipient umbels than do smaller ones. We showed that experimental removal of staminate flowers lowers fruit set only in primary umbels. We used stepwise multiple regressions to examine the effects of staminate flowers on xenogamous pollination, overall (xenogamous and geitonogamous) pollination and fruit set. The regressions revealed significant effects of staminate flowers only for cross pollination of primary umbels. We concluded that in P. montanus, staminate flowers function primarily as pollen donors.