Floral micromorphology of the genus Restrepia (Orchidaceae) and the potential consequences for pollination

- Restrepia is a small Pleurothallid genus facing habitat loss.
- Floral organs were imaged using SEM and macro-photographic techniques.
- Restrepia exhibits non-nectar rewarding myophily.

Restrepia is a small Pleurothallid genus, comprising 57 species, 44 of which were discovered since 1970. These species are indigenous to Central and South America, where their montane forest habitats are under increasing pressure from changes in land use. With resulting increasingly fragmented habitats and dwindling numbers, the pollination systems of obligate out-breeding genera, such as Restrepia, may no longer function efficiently which could potentially lead to their extinction. As such, the main aim of the current study was to perform an in-depth investigation of floral structures in the genus, using SEM and photographic technology to formulate a putative pollination mechanism for these species.The floral micromorphology of dorsal sepal and lateral petal osmophores, synsepal, labellum, cirrhi and calli were investigated by scanning electron microscopy (SEM), macro-photography and quantitative analyses of some floral proportions.The secretory nature of the labellum, synsepal and osmophore papillae were established and the calli were shown to possess a unique papillate, non-secretory structure. A pollination mechanism for the genus was proposed which includes the role of the scent trails produced by the osmophores and the 'trapping' role of the cirrhi. A 'functional fit' between the flower and the pollinator is suggested. In conclusion, we consider Restrepia to represent a non-nectar rewarding and 'deceptive' orchid genus and that this pollination mechanism may be directly linked to the breeding system (gametophytic self-incompatibility) in this genus.