Two regions, two lineages: Untangling two centuries of confusion between Machilus glaucescens and M. macranthus (Lauraceae) through integrative taxonomy.

The Asian genus Machilus (Lauraceae) of the Persea group is widely distributed across South and Southeast Asia. Like many other genera of Lauraceae, Machilus has received limited systematic attention, particularly in India. As a result, the nomenclature and systematic positions of Machilus glaucescens (Nees) Wight and M. macranthus Nees have remained unclear. In this study, we employed an integrative taxonomic approach to disentangle the taxonomy, phylogenetic relationships and distributions of M. glaucescens (restricted to Indo-Burma biodiversity hotspot) and M. macranthus (restricted to Eastern Ghats and Western Ghats-Sri Lanka biodiversity hotspot). We analysed morphological, molecular, and distribution data to elucidate the systematic relationships following the mix-up of taxonomic status. We examined 28 morphological characteristics using cluster analysis and reconstructed phylogenies with two nuclear markers (ITS and LEAFY intron II). Additionally, we studied the distribution range of both species with ecological niche modelling. The combined evidence from nomenclature, morphological clustering, phylogenetic analyses, as well as the species distributional range limits confirms that M. glaucescens and M. macranthus are two distinct species with their current distributions restricted to separate biogeographic regions of Asia.