Unexplored Amazonian diversity: rare and phylogenetically enigmatic tree species are newly collected

Abstract

The Amazon is renowned to hold an unprecedented, yet poorly-known or unexplored plant diversity. This study aimed to report new collections on five rare or little-known and phylogenetically enigmatic trees, Aguiaria excelsa (Malvaceae, Bombacoideae), Hylocarpa heterocarpa (Humiriaceae), and the papilionoid legumes Monopteryx uaucu, Petaladenium urceoliferum, and Uleanthus erythrinoides, that became available after recent fieldwork in the western and central Brazilian Amazon region. All five genera, except for Monopteryx, are monospecific and represented in herbaria by only the type or at most few collections made more than 30 years ago. Comments on morphological affinities, never-seen-before photographs, and a distribution map of all species are given. A lectotype for U. erythrinoides is here designated. We also provide a complete taxonomic description for P. urceoliferum, whose pods until presently were unknown. Since these genera are missing branches in the molecular phylogenetic trees of Leguminosae, Humiriaceae, and Malvaceae, the opportunity to include them in future phylogenetic studies will certainly clarify the evolutionary history and taxonomy of their respective families. The