Nectar-mediated avian pollination in Cattleya (Orchidaceae: Laeliinae).

Abstract

Orchids are notable for the variety of rewards produced for their pollinators. Nevertheless, many species are rewardless and pollinated by food-deceptive strategies. This is the case for Cattleya, a Neotropical genus of more than 100 species supposedly pollinated by food-deception. Here, I studied a member of the clade Sophronitis (Cattleya cernua) in forest areas of southeastern Brazil. The study included analyses of floral morphology, light microscopy of secretory tissues, histochemistry of flower resources, and measurements of nectar volume and concentration. Data on pollinators and mechanisms of pollination were collected in the field by means of film records, while breeding systems were studied using experimental treatments applied to cultivated specimens. The flower traits of Cattleya cernua show strong adaptation to avian pollination. Flowers produce 1-7 μl of a moderately concentrated nectar (17-50%). A secretory tissue at the distal portion of the cuniculus is responsible for nectar secretion. Secreted nectar is stored in the nectar chamber. Pollinaria deposition on the apex of bird beaks allows both short- and long-billed birds to pollinate the flowers. Plants from the studied population were fully self-compatible but pollinator-dependent. Pollinator frequency was higher than in food-deceptive Cattleya. As far as is known, this is the first record of nectar production in Cattleya. The discovery of a reward-producing species (C. cernua) within a genus entirely pollinated by food-deception strategies (Cattleya) provides clues and new insights into understanding the diversification of Laeliinae across the Neotropics.