Taxonomic revision of Mussaenda wallichii (Rubiaceae): two new synonyms from Southeast Asia

Mussaenda wallichii G. Don (Rubiaceae) is a widespread species distributed from northeastern India to Southeast Asia, but its taxonomic delimitation has remained uncertain due to overlapping morphological characters and incomplete assessment of type materials. Based on extensive herbarium examinations, including type specimens, and critical evaluation of protologues, we reassessed the taxonomic identities of M. intuspilosa Jayaw. and M. lancipetala X.F. Deng & D.X. Zhang. Morphological comparisons revealed that both taxa are conspecific with M. wallichii and cannot be distinguished from it by consistent diagnostic characters. Therefore, they are treated as heterotypic synonyms of M. wallichii . Lectotypification of historical names is also discussed. This study furthers our understanding of morphological variation, species diversity, and distribution patterns within Mussaenda in Southeast Asia.