Floral volatile profile in Pleurothallidinae, an orchid subtribe pollinated by flies: ecological and phylogenetic considerations

The Pleurothallidinae are recognized as the largest orchid group pollinated by Diptera. This subtribe has been focus of ongoing phylogenetic studies, in which the floral biology and mating systems of their representatives have been recently assessed and some synapomorphies pointed out, all of them regarding features or processes occurring in flowers. Data about the flower volatiles are still scarce, although it may offer valuable information about the floral biology of this subtribe. Here, we collected and analyzed the volatiles emitted from flowers at anthesis. We selected seven Brazilian species representing both late and early-divergent clades of Pleurothallidinae aiming to describe the chemical profile of flower volatiles and relate the identified compounds to the reproductive biology of the selected species. The outstanding feature regarding the floral scent profile is the ubiquitous occurrence in remarkable concentrations of alkanes, a situation not found in Laellinae, a closed subtribe of Pleurothallidinae. We also present a discussion concerning the ecological aspects of the flower volatiles and their pollinators.