Integrative taxonomic assessment reveals a new species of Sigmoidotropis (Leguminosae) from northeastern Brazil

Integrative analyses combining nrITS and trn K/ mat K phylogenetic analyses, palynology, ecological niche modelling, and morphology were conducted to reassess species limits within the Neotropical genus Sigmoidotropis (Leguminosae). Our phylogenetic framework recovered well-supported clades that clarify previously ambiguous relationships and revealed a distinctive lineage endemic to humid forest enclaves in northeastern Brazil. Palynological traits, together with diagnostic morphological features, provide additional evidence for its separation from closely related taxa. Ecological niche modelling further supports the ecological isolation of this lineage, indicating distribution restricted to cooler and moister upland refugia embedded within the seasonal Caatinga domain. The integration of multiple data sources consistently confirms the uniqueness of this taxon, here described as a new species, S. carolinae . Our results highlight the underestimated diversity within Sigmoidotropis and underscore the evolutionary and biogeographical significance of humid forest refugia in shaping species diversification across northeastern Brazil.