The phenology, floral morphology, pollination mechanisms and reproductive biology of Grobya amherstiae Lindl. were studied in two populations located in altitudinal forests at Serra do Japi, Jundiaí, São Paulo State, Brazil. The flowering occurs in summer and lasts about one month (part of February and March). The flowers of an inflorescence open almost simultaneously, in the morning, and each lasts about seven to eight days. The flowers release a honey-like fragrance. At both populations G. amherstiae was pollinated by Paratetrapedia fervida Smith (Anthophoridae) bees, which collect floral oils produced by trichomatic elaiophores at the apex of the lip and the column basis. At one of the populations, besides bees individuals of a Curculionid beetle of the genus Montella were recorded, which perform self-pollination on the majority of the flowers. Grobya amherstiae is self-compatible but pollinator dependent. The females of Montella sp. oviposit in the ovary and their larvae consume the seeds. However, the number of fruits parasitized by the larvae is low when compared with the amount of fruits produced. Since natural fruit set is low, the beetles contribute positively for the reproductive success of G. amherstiae at least in one of the populations.
floral biology; Grobya; Orchidaceae; pollination; reproductive biology
