Floral synomone components of fruit fly-attracting orchids, Bulbophyllum sinapis and B. hahlianum, in Papua New Guinea

Abstract

Papua New Guinea (PNG) is known as the center of diversification of the largest orchid genus Bulbophyllum . In order to understand the ecological adaptation mechanisms in two closely related Dacini fruit fly-attracting orchids species, B. sinapis and B. hahlianum, their floral synomone components were examined. Flowers of B. sinapis attract males of various agricultural pest fruit fly species, such as Bactrocera musae and Ba. umbrosa, with methyl eugenol (a phenylpropanoid). However, flowers of B. hahlianum, attract fruit fly males belonging to a more diverse group of cue-lure-responsive species, namely, Ba. frauenfeldi, Ba. bryoniae and Zeugodacus cucurbitae with a mixture of phenylbutanoids including anisyl acetone (AA), raspberry ketone (RK) and zingerone (ZN). Contents of the volatiles in floral parts of both species were quantified. The highest contents of floral volatiles were detected in the lateral sepals of both the Bulbophyllum species. Attractant activity of synthetic AA, RK and ZN was examined in a local habitat in East New Britain. Furthermore, male flies attracted to B. hahlianum were found to sequester RK in the body tissues in varying quantities, which suggests its role as a sex pheromonal component to attract conspecific females as in the case of other Dacini fruit fly species through pharmacophagous acquisition of the orchid synomone. • Papua New Guinean orchids attract males of Dacini fruit flies with floral volatiles (83). • Floral synomone possesses either phenylpropanoid or phenylbutanoid male attractants (83). • Consume floral volatiles used by male flies as sex pheromone to attract females (80). • Biochemical and phylogenetic relationships of daciniphilous orchids are examined (80).