Cleistes macrantha (Barb. Rodr.) Schltr. is widely distributed in Atlantic rain forests in south and southeastern Brazil, occurring in anthropogenic disturbed areas and in "restinga" vegetation. Aspects of the floral biology of C. macrantha were investigated in the Intervales nature reserve, in the interior of São Paulo state. This species offers nectar as reward and is pollinated principally by bumblebees. The nectar is secreted before the anthesis of the flowers, with no posterior secretion. Hermit hummingbirds can also act as pollinators. A previous visit of a bumblebee, however, is necessary for pollen deposition on their bills. Bumblebees are responsible for most cross-pollinations. The hummingbirds perform mainly self-pollination. Preliminary treatments reveal that C. macrantha is self-compatible, but a pollinator is necessary for successful pollination. In spite of the self-compatibility observed, ecological factors favor cross-pollination in this species. This study makes too, a comparison of the floral biology of C. macrantha with what is known about the genera of the North American-Asiatic clade in Pogoniinae.
Cleistes; floral biology; Orchidaceae; Pogoniinae; pollination
