Vanilla × robusta (Orchidaceae: Vanilloideae), the first natural Vanilla hybrid for South America

Abstract

Hybridization plays a relevant role in the evolution and diversification of flowering plants. Natural hybridization has been recorded in many orchid genera, including Vanilla. During surveys performed in Brazilian biomes, a plant with characteristics intermediary between V. phaeantha and V. pompona was found. The plant corresponds to a natural hybrid between these sympatric species, and is described here as V. × robusta. A morphological comparison with the parental species is presented, along with an illustration based on living specimens, and its geographic distribution. Vanilla × robusta is recognized by its long and asymmetric leaves that are longer than the internodes. The flowers of V. × robusta present characteristics intermediary between V. phaeantha and V. pompona. The shape, the size and the coloration of the labellum of V. × robusta is clearly intermediary between the parental species. The labellum of the nothospecies is discretely 3-lobed, while in V. phaeantha this structure is distinctly 3-lobed. In V. pompona the labellum is 1-lobed to obscurely 3-lobed. To date, V. × robusta is only known from a single locality in southeastern Brazil. Extensive field work, besides accurate morphological analysis of parental species was crucial to elucidate its hybrid origin. Since the occurrence area and the flowering season of V. pompona and V. phaeantha sometimes overlap, they share some Eulaema species as pollinators, and they are inter-compatible, it is plausible that the natural hybridization event documented here is not an isolate case.