Mimesis of bellflower (Campanula) by the red helleborine orchid Cephalanthera rubra

Abstract

The spectacular red helleborine orchid (Cephalanthera rubra) is distributed from Iran throughout the Mediterranean region and up to western Europe, reaching southern Scandinavia1. The plant preferably grows on calcareous soils in dry woods2. The elongate, loose inflorescence usually bears 4-10 brilliantly rose-coloured flowers which completely lack nectar or other food for anthophilous insects and thus act by deceit 3. Flower-visitors so far reported are bees4-6, especially males of the solitary bees Chelostoma fuliginosum (Pz.) (= Chelostoma rapunculi (Lep.) = Chelostoma nigricornis (Nyl.)) and Chelostoma campanularum (K.) (Megachilidae). Females of the two Chelostoma species collect pollen for their brood almost exclusively from bellflowers (Campanula)7. Mate-seeking flights, feeding and resting of the males are strongly associated with Campanula flowers. I now report that C. rubra mimics the floral coloration of Campanula in the bee visual system and thereby receives pollination service by the Chelostoma males. Pollination is regularly effected by males of C. fuliginosum. The orchid peaks in anthesis distinctly before Campanula, phenologically matching and efficiently exploiting the male bee population. © 1983 Nature Publishing Group.