The major fruit fly attractant component in the floral fragrance of
Bulbophyllum cheiri (fruit fly orchid) is methyl eugenol (ME). In the lowland rain forest of Malaysia, the solitary and nonresupinate flowers of the fruit fly orchid attract only males of the ME-sensitive fruit fly species (
Bactrocera carambolae,
B. papayae, and
B. umbrosa. During the morning, the fruit fly orchid flower is visited by many fruit flies, which can sometimes cover the whole flower. The number of visitors dwindles in the afternoon. Headspace analysis of the flower shows a high ME peak in the morning, a small one between 12:00 and 14:00 hr, and no detectable ME peak after 14:00 hr. The process of pollination in the wild is initiated by attraction of fruit flies to floral ME. The flower, with the aid of its specialized hinged see-saw lip (labellum), temporarily traps (<1 min)="" a="" fruit="" fly="" pollinator="" between="" its="" lip="" and="" column.="" just="" prior="" to="" this,="" the="" fly="" is="" rewarded="" by="" the="" opportunity="" to="" feed="" on="" the="" floral="" attractant="" found="" on="" surfaces="" of="" petals,="" sepals,="" and="" lip.="" the="" pollinaria="" borne="" by="" two="" wild="">1>
B. papayae males (caught on and near the fruit fly orchid flower) are identical in morphology and structure with those obtained from the flower. Many of the
B. papayae males (17 of 22 analyzed) attracted to the fruit fly orchid already possessed both ME metabolites,
trans-coniferyl alcohol and 2-allyl-4,5-dimethoxyphenol, in their rectal glands, indicating that they had previously consumed ME. In this orchid–fruit fly association, both organisms gain direct reproductive benefits: the orchid flower gets pollinated without having to offer nectar, while the fruit fly boosts its pheromone and defense system, as well as its sexual competitiveness by feeding on the ME produced by the flower.
Bulbophyllum cheiri
- fruit fly orchid - Orchidaceae - fruit flies - Tephritidae Bactrocera spp. - methyl eugenol - floral scent - pheromone - synomone - pollination - coevolution