Generalized food-deceptive pollination in four Cattleya (Orchidaceae:Laeliinae) species from Southern Brazil

Abstract

We studied the breeding system and pollination biology of Cattleya coccinea, C. intermedia, C. purpurataand C. tigrina in native populations from Rio Grande do Sul, Southern Brazil. At the State level, the threelatter species are considered under risk of extinction and this work is intended to be a contributiontowards their conservation and management. To date, their pollination needs and breeding system remainunknown.Breeding system was elucidated through controlled pollinations applied to isolated plants. Pollinationwas studied in the field, by means of photographic and filmic records. Cattleya purpurata, C. intermediaand C. tigrina are pollinated by large native Apidae bees of the genera Bombus, Xylocopa and Epicharisthat bear the pollinaria on the scutellum and mesonotum. In spite of their differences in colour andperianth size, bee-pollinated species share a number of flower features which are absent in C. coccinea. Thelatter species is pollinated by the hummingbird Chlorostilbon lucidus (Trochilidae). In agreement, flowersof C. coccinea present a set of flower features normally associated to ornithophily. All studied specieslack rewards and deceive their food-seeking pollinators. All species are self-compatible but pollinator-dependent. Fruiting success following manual self-pollination and cross-pollination did not differ, exceptin C. coccinea. However, in all species fruit from cross-pollinations yielded significantly higher numbersof viable seed. All studied species displayed low visitation rates, low natural fruit set (ranging from 0.5to 14%) and Nilsson’s male efficiency factor of less than one, indicating that less than one flower waspollinated per pollinarium removed.All these features are consistent with those of other orchid groups pollinated through generalizedfood-deception.