The pollination ecology of Listera ovata (Orchidaceae)

Abstract

Interactions betweenListera ovata(L.) R. Br. and anthophilous insects were observed on Öland and in Uppland, Sweden, during 1974–1980. The pollen vectors were mainly ichneumons (Hymenoptera Parasitica, Ichneumonidae), saw–flies (Hymenoptera Symphyta) and beetles (Coleoptera). These three groups transported on Oland 56, 28 and 10% and in Uppland 28, 54 and 15% of the pollinia. The most common visitors were Diptera. In the Ichneumonidae, males were on average over three times as frequent as females and carried 81% of the pollinia. Various data indicated anthecological specialization to about 8–12 mm long, relatively strong insects, which show abundance and diversity in the biotopes withL. ovata.They have medium–sized almost hairless heads with short and rather small mouth–parts. Perhaps optimal interaction takes place with ichneumon males. Since floral adaptation to the legitimate group obviously includes generalized chemical attractants and complete accessibility of nectar, the spectrum of visitors reaches that of an umbelliferous plant. The touch–sensitive rostellum has probably induced evolution of the long nectariferous furrow on the labellum surface. The floral fragrance is essentially a terpene–blend. Experiments indicated strict entomogamy.