Multilocus Phylogenetics of Tribe Semecarpeae (Family Anacardiaceae) Sheds Light on the Taxonomic Status of Holigarna, and its Palaeo-Dispersal Pathways

ABSTRACT Recent molecular systematics have challenged the traditional classification that relies solely on phenotypic characteristics, prompting a re-evaluation of the taxonomic status of any genus. Indo-Malayan genus Holigarna, known for its ethnomedicinal values, has traditionally been classified within the tribe Semecarpeae of family Anacardiaceae. The present study affirms the taxonomic position of the Holigarna within a phylogenetic framework by the inclusion of molecular sequences of the genus for the first time. The modern leaf samples were collected for four Holigarna species, from their natural habitats in Kerala, India and sequenced for eight gene markers, including two nuclear (ITS and ETS), five plastids (rps16, trnL-trnF, matK, rbcL, and psbA-trnH) and small subunit ribosomal RNA. Molecular topology affirms the taxonomic position of Holigarna within the tribe Semecarpeae, comparable to the traditional taxonomic classification, and supports the monophyletic nature of the genus, suggesting that its species are closely related to each other. Due to scarce fossil evidence of Holigarna, the evolutionary and palaeobiogeographic history is partially understood. The fossils retrieved from the Indian subcontinent indicate that Holigarna might have originated around or before the early Palaeogene in the Old World, and diversified on the Indian subcontinent and later got dispersed to Asia, suggesting the “Out-of-India” dispersal. This dispersal scenario also highlights the significant role of the Indian subcontinent in the diversification of this family.