An evaluation of the taxonomic status of Musa viridis and Musa splendida using high-throughput sequencing data

Abstract

The delimitation of species based on morphological traits can be challenging due to overlapping trait variation. The taxonomic identity of closely related sympatric species with individuals displaying intermediate phenotypes is particularly questionable. However, thorough morphological assessments or traditional molecular analyses often lack resolution to clarify if two species are truly separate taxonomic entities or should be merged. Interestingly, advances in high-throughput sequencing methods and data processing during the last decades enable the use of high-resolution data to tackle taxonomic problems. Several species with an unclear taxonomic status are found in the banana family (Musaceae). In Vietnam, the Musa species M. viridis and M. splendida have very similar morphological trait characteristics. The main difference between the two species is the colour of the male flower bud: M. splendida has red flower buds, whereas M. viridis has pink flower buds. Both species occur sympatrically, and individuals with red and pink male flower buds are found together in some populations. In this study, we used high-throughput (DArT) sequencing data from plants of nine populations to investigate the taxonomic status of these Musa species. Maximum likelihood phylogenetic trees were reconstructed for over 12,000 loci (< 120 base pairs) and one ASTRAL consensus tree was created from all locus trees. The individuals in the ASTRAL phylogenetic tree did not cluster by species identity, but by population, having individuals from different species in the same cluster. Consequently, we propose to merge the species M. viridis and M. splendida into one species named M. splendida according to nomenclatural conventions.