Coalescent-Based Species Delimitation in Herbaceous Bamboos (Bambusoideae, Olyreae) from Eastern Brazil: Implications for Taxonomy and Conservation in a Group with Weak Morphological Divergence Coupled with Low Genetic Diversity

Species delimitation in herbaceous bamboos has been complex and, in some genera, a great part of its diversity has been confirmed only based on genetic information, as is the case of the genus Raddia. It includes nine species, all occurring in Brazil, but only R. portoi predominates in dry forests of the Northeast associated with the Caatinga phytogeographic domain. This species is morphologically close to R. angustifolia, which is known for a single location in the Atlantic Forest in Southern Bahia, and is considered to be threatened by extinction. Besides problems with taxonomic focus, actions for its conservation are complicated because it is not certain if it must be considered an independent species or included in the more widespread R. portoi. In this study, we used coalescent multispecies (MSC) theory approaches combined with genetic structure analyses in an attempt to delimit these two species. Different analyses were congruent and the species delimitation using MSC inferred distinct lineages supporting their recognition as two species. These results solved the taxonomic doubts and also showed the power of these approaches to delimit species as lineages, even in groups with weak morphological divergence and low genetic variability, and also impacting our knowledge for conservation purposes.