Evidence of floral rewards in Brasiliorchis supports the convergent evolution of food‐hairs in Maxillariinae.

Premise: Angiosperms distributed over a large geographical area may display considerable phenotypic variation that can be recognized at morphological and micromorphological levels. Here, we investigate the pollination biology and the presence of floral rewards in Brazilian populations of the widely distributed orchid, Brasiliorchis picta. Based on the new data presented here this study investigates the evolution of floral rewards in Maxillariinae, and tests for the occurrence of convergent evolution of food‐hairs in this subtribe. Methods: Micromorphological and histochemical analyses of the labellar tissues were conducted, together with chemical analysis of fragrance and experiments involving the use of chemical baits. The evolution of floral rewards in Maxillariinae were addressed. Results: Microscopy revealed that B. picta offers food‐hairs as a reward. Fragrance is produced by abaxially located labellar epidermal papillae. The main compound present in our samples (2‐phenylethanol) also occurs in the aggregation pheromone produced by the mandible glands of pollinators, Meliponini bees. Our analyses indicate a high diversity of flower rewards and pollinators displayed by members of Maxillariinae, and support that edible trichomes evolved independently five times in the subtribe. Conclusions: The high diversity of floral rewards and pollinators displayed by members of Maxillariinae suggests that different pollinator pressures are involved in the evolution of this neotropical subtribe. In addition, the offering of food‐hairs, which are generally infrequently encountered in Orchidaceae, arose by convergent evolution in Maxillariinae. [ABSTRACT FROM AUTHOR]