Pruning the polyphyletic genus Polyalthia (Annonaceae) and resurrecting the genus Monoon

Abstract

The highly polyphyletic status of the species-rich genus Polyalthia (Annonaceae) remains one of the most significant impediments to revisionary and floristic taxonomic research in the family. Although Polyalthia has recently been reduced in taxonomic scope, the remaining species in the genus still form a phylogenetically disparate and morphologically heterogeneous assemblage. We use maximum parsimony, maximum likelihood and Bayesian phylogenetic reconstructions based on chloroplast DNA sequence data (matK, rbcL, trnL-F) to show that the remaining Polyalthia species segregate into three clades: a clade sister to Miliusa; a clade that also includes all Enicosanthum and Woodiellantha species sampled, sister to Neo-uvaria; and a clade that also includes all Haplostichanthus species sampled, inferred (based on previous research) to be sister to Popowia. Diagnostic morphological and anatomical characters are evaluated for the latter two clades, and diagnostic leaf and seed characters identified. Based on these results, the generic name Monoon is resurrected for the clade that includes Enicosanthum and Woodiellantha, following the transfer of 37 species from Polyalthia s.l., 18 species from Enicosanthum and the single Woodiellantha species. The generic name Haplostichanthus is furthermore synonymised with Polyalthia s.str., necessitating nine nomenclatural changes, including six new combinations and three replacement names.