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

The highly polyphyletic status of the species-rich genus <I>Polyalthia</I> (Annonaceae) remains one of the most significant impediments to revisionary and floristic taxonomic research in the family. Although <I>Polyalthia</I> 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 (<I>matK</I>, <I>rbcL</I>, <I>trnL-F</I>) to show that the remaining <I>Polyalthia</I> species segregate into three clades: a clade sister to <I>Miliusa</I>; a clade that also includes all <I>Enicosanthum</I> and <I>Woodiellantha</I> species sampled, sister to <I>Neo-uvaria</I>; and a clade that also includes all <I>Haplostichanthus</I> species sampled, inferred (based on previous research) to be sister to <I>Popowia</I>. 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 <I>Monoon</I> is resurrected for the clade that includes <I>Enicosanthum</I> and <I>Woodiellantha</I>, following the transfer of 37 species from <I>Polyalthia</I> s.l., 18 species from <I>Enicosanthum</I> and the single <I>Woodiellantha</I> species. The generic name <I>Haplostichanthus</I> is furthermore synonymised with <I>Polyalthia</I> s.str., necessitating nine nomenclatural changes, including six new combinations and three replacement names.