Reproductive biology and pollinator limitation in a deceptive orchid, Serapias vomeracea (Orchidaceae)

Abstract

Deceptive orchid species that offer no floral rewards to pollinators often experience pollinator limitation. Serapias vomeracea is considered a particular example of terrestrial orchids using deceptive strategies because its sepals, petals and the lateral lobes of the hypochile form a small tube imitating a little hole that the insects use to rest. The pollination biology and breeding system were investigated in two populations of S. vomeracea in order to examine the extent of pollinator limitation. Visiting insects were immobile in the Serapias flowers during the early morning and late evening. The main pollinators were Oedemeridae and Lymexylidae (Coleoptera), but Hymenoptera (Ceratina, Eucera, Osmia) were also observed. Fruit set did not vary in response to floral display size, suggesting that variations in flower number per inflorescence and plant height were not responsible for attracting pollinators and thus reproductive success. Although S. vomeracea is self-compatible, bagged inflorescences produced no fruits. Artificial pollination resulted in 95–100% fruit set by induced autogamy, 95–100% by geitonogamous pollination and 90–95% by xenogamous pollination. Fruit set in the open-pollinated control was 13–18%. Fruit production was not related to the size, number or position of flowers. Pollinator observation and supplemented hand-pollination indicated a positive relationship between fruit set and pollinator visitations in this species.