The discovery of a new giant legume tree species in a severely fragmented landscape underscores the alarming threats to the biodiversity of the Brazilian Atlantic Forest

Abstract The Brazilian Atlantic Forest domain has one of the highest levels of plant species endemism, but the intense historical fragmentation across the coastal Atlantic tropical rain forest has reduced the original vegetation to < 10% and an island-like, patchy landscape. Despite such unprecedented vegetation loss, biogeographically and phylogenetically interesting discoveries in different angiosperm families have been newly reported for the Atlantic Forest in recent years. Here, we show that species discovery in the legume family (Fabaceae) across the Atlantic Forest has counter-intuitively been increasing. Since 1850, more than half of the legume species described for the domain are endemic, and the total number of endemic species has since increased almost four-fold, resulting in the current record of 442 endemic legumes. One such endemic is a new papilionoid legume, only known from a few giant trees that remained misidentified for 70 years since it was first collected. This new species, described here under the name Dipteryx hermetopascoaliana, based on morphological, geographical and molecular evidence, represents the first endemic species to the genus in the Atlantic Forest. We provide a complete morphological description, distribution map, preliminary conservation status and illustration of the new species. The phylogenetic isolation of D. hermetopascoaliana as sister to all other species of the genus and its restricted distribution in a severely fragmented landscape isolated by sugarcane monocultures in north-eastern Brazil are a signature of how critically endangered the biodiversity of the Atlantic Forest is.