Jacarandás in Focus: Integrative Taxonomy of the Machaerium acutifolium Complex (Leguminosae, Papilionoideae) Reveals Two New Species from Brazil
Abstract
Abstract— The neotropical jacarandá species of the Machaerium acutifolium complex (Leguminosae, Papilionoideae) are among the most widely distributed in the genus, occurring in six countries of South America, where it displays great ecological and economic importance. Across its distribution in almost all Brazilian biomes, M. acutifolium presents an evident phenotypic plasticity, mainly in the shape and size of the leaflets, that led to the description of different taxonomic entities over the years. However, the significant morphological variation observed within the complex’s species prompts consideration for further studies. Here, we re-evaluate the taxonomic delimitation within the M. acutifolium species complex using morphometric and bioclimatic data. A nomenclatural review and morphological assessment of M. acutifolium and related species were carried out to support morphometric analyses of 23 vegetative and 27 reproductive characters, from a total of 99 specimens as well as eco-geographic features of 131 specimens. To expand the sampling, which was mostly based on the measurement of herbarium specimens, we also carried out fieldwork in the Brazilian Caatinga and Cerrado phytogeographic domains with focus to collect some poorly known, yet morphologically unusual populations. Our results reveal three morphologically well delimited entities with distinct habitat preferences and/or geographic ranges. Based upon these discoveries, we describe and illustrate two new species from Brazil comprising material previously assigned to M. acutifolium : M. lewisianum and M. paganuccii . We provide complete descriptions and line drawings for these new taxa, also an updated species description of M. acutifolium , as well as information on habitat, distribution, phenology, taxonomic comments, and photographs alongside its conservation status based on IUCN red list categories. Keywords —Bioclimatic variables, Dalbergieae, endemism, Fabaceae, IUCN Red List, multivariate analysis, principal component analysis.