Unravelling the species diversity, phylogeny and biogeography of the mycoheterotrophic Voyrieae (Gentianaceae) and the description of a new species

Abstract

Because different tropical forest regions possess their own species diversity and communities, it is crucial to investigate the diversification history of their biota to understand how biodiversity was assembled. However, this requires reliable species concepts and robust, well-sampled phylogenies. Here we focus on the fully mycoheterotrophic genus Voyria (Gentianaceae) and its diversification history in the Neotropics. We use a likelihood-based approach to test species boundaries in Voyria with a population-level ITS dataset and we build an extensive multigene species-level phylogenetic framework for Voyria, which we use to infer the biogeographic evolution of the genus. We find strong support for the established morphology-based species delimitation in this genus but we also discover a new species, which we describe here. Ancestral area reconstructions place the origin of the Voyrieae in the Guianas. Frequent exchange with other forest regions is inferred to have started from the Oligocene and continued toward the present. In these exchanges, the Guianas appeared to have acted as the most important source, while other regions mainly functioned as sinks. We conclude that well-sampled phylogenies of fully mycoheterotrophic plants, which are ecologically restricted to rainforest habitats, can be instrumental to test hypotheses on rainforest biome evolution.