Floral scents affect reproductive success in fly-pollinated Alocasia odora (Araceae)

We evaluated the role of floral scents in the reproductive success of Alocasia odora C. Koch (Araceae). Alocasia odora is pollinated by its specific pollinators, Colocasiomyia alocasiae (Okada) and C. xenalocasiae (Okada) (Diptera: Drosophilidae). These flies use the spadix of A. odora as breeding sites. The appendix, which is at an upper part of the spadix and is the most attractive region, attracted these pollinators by emitting volatiles, although the male zone of the inflorescence was also attractive. The number of flies attracted was positively correlated with appendix size. During the pistillate phase of the protogynous spadix, attracted flies aggregated in the lower part (female zone) to mate, lay eggs, and perhaps obtain nutrients. The flies moved to the upper part (male zone) of the spadix by the tightening of the constriction separating the upper and lower parts, and then the staminate phase started. This movement of the flies on the spadix promotes outcrossing of A. odora. Removal of the appendix or the whole upper part of the spadix resulted in much reduced fruit set, suggesting that the absence of the scent-producing region leads to insufficient pollination because of reduced pollinator attraction.