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

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