Taxonomic updates to Artocarpus subgenus Artocarpus (Moraceae) and allied taxa with a particular focus on the species native to Singapore

The breadfruit genus Artocarpus J.R.Forst. & G.Forst. (Moraceae) has sixteen species in Singapore, fourteen of them native. In this precursory study to the treatment of Artocarpus for the Flora of Singapore, we present updated phylogenomic analyses of Artocarpus subgenus Artocarpus based on 517 nuclear genes. The following taxonomic changes based on recent phylogenetic analyses, review of herbarium specimens, and field observations, are proposed. Artocarpus subg. Cauliflori (F.M.Jarrett) Zerega is reduced to a section within Artocarpus subg. Artocarpus, and Artocarpus sect. Glandulifolium F.M.Jarrett is raised to subgenus status. The new monotypic subgenus Artocarpus subg. Aenigma E.M.Gardner & Zerega is proposed for Artocarpus sepicanus Diels, whose phylogenetic position remains uncertain and may be of ancient hybrid origin. Artocarpus elasticus Reinw. ex Blume, A. scortechinii King and A. corneri Kochummen are recognised as distinct species. Artocarpus clementis Merr. is reinstated as distinct from A. lanceifolius Roxb. Artocarpus calophyllus Kurz and A. melinoxylus Gagnep. are reinstated as distinct from both A. chama Buch.-Ham. and A. rigidus Blume. Artocarpus nigrescens Elmer is reinstated as distinct from A. treculianus Elmer. Keys to the subgenera, the sections of Artocarpus subg. Artocarpus and to the species found in Singapore are presented. A nomenclatural synopsis of subgenera Artocarpus, Aenigma and Glandulifolium is presented with taxonomic notes to aid in identification. Seventeen lectotypes, six of them in a second step, and two neotypes are designated.