The effects of inflorescence size and flower position on female reproductive success in three deceptive orchids

Most Mediterranean orchids are deceptive, offering no reward to insect pollinators. In theabsence of a reward, inflorescence size and flower position within inflorescence may be associated with thetiming and the numbers of pollinators attracted, thus influencing the final reproductive success. Pollinationbiology and breeding system were investigated in three deceptive orchids, Orchis italica, O. anthropophora,and Anacamptis papilionacea. Although all examined orchids were self-compatible, bagged inflorescencesproduced no fruits. Artificial pollination resulted in a 76-79% fruit set by induced autogamy, a 70-76% oneby geitonogamous pollination, and a 79-87% one by allogamous pollination. The natural fruit set in the openpollinatedcontrol was 14-16%. Fruit production was neither related to the inflorescence size, nor to thenumber and position of flowers within the flowering spike, suggesting that variation in these floral traits doesnot influence pollinator attraction or female reproductive success.