New canopy legume species highlight liana gap sampling across Amazonian and Atlantic rain forests

Abstract Lianas are a key component of the Neotropical flora, accounting for 10% of angiosperm richness and playing important ecological roles. However, the canopy preference of some species often leads to their underrepresentation in herbarium collections, thereby exacerbating Linnaean, Darwinian, and Wallacean shortfalls. The papilionoid legume genus Macropsychanthus exemplifies this challenge, with 37% of its species documented from 10 or fewer herbarium collections. In this study, we describe two new species represented by only one or two collections made during the early to mid‐20th century and assess their phylogenetic position within the genus. Additionally, we compiled a preliminary list of Brazilian legume liana species documented from five or fewer collections and modeled their potential niche distributions to assess whether these species could be distributed more broadly. We identified a total of 55 liana species with five or fewer collections, representing 20% of Brazilian legume liana species. Of these, 28 species are from the Amazon, 23 from the Atlantic Forest, 2 from the Cerrado and 2 from the Caatinga. Species from the Amazon, Caatinga, and Cerrado tend to have broader potential distributions across their respective biomes, whereas those from the Atlantic Forest are generally more narrowly restricted. Our findings highlight the urgent need for comprehensive botanical surveys in Neotropical humid forests to address critical knowledge gaps in plant diversity.