A synopsis of the genus Lepidagathis (Acanthaceae) in India, new taxa and notes on Dalzell's species

Nicolas Alexander Dalzell (1817–1878) described seven species of Lepidagathis (Acanthaceae). Except for Lepidagathis grandiflora, which was later recognized as Calacanthus, all are retained in the genus Lepidagathis. Of these, five are endemic to peninsular India. While exploring Dalzell’s species, we have made field explorations, consulted Lepidagathis collection at different herbaria, and presented here a synopsis of the genus in India. The nomenclature, taxonomy, distribution, and The International Union for Conservation of Nature (IUCN) threat status of Lepidagathis species in India are reviewed. Nomenclature and taxonomic notes on L. cristata and L. cuspidata and the infraspecific taxa in L. pungens, L. incurva are provided. Lepidagathis aristata, a Malaysian species is resurrected; a new name Lepidagathis forskaolii is proposed for the oldest basionym Ruellia aristata. Lepidagathis clavata, L. prostrata, and L. rigida are rare, and only known by a few collections, L. lutea is confined to Konkan and adjoining areas. Lepidagathis cuspidata is collected from its entire geographic range and an overlooked variety, L. cuspidata var. stenostegia is resurrected. Based on live and herbarium collections, a riverine, elliptic-linear-leaved variety elliptica is proposed. Lepidagathis dalzellii, a large flowered new species, allied to L. cuspidata from the United Nations Educational, Scientific and Cultural Organization (UNESCO) World Natural Heritage Site (Kaas plateau, Maharashtra) is also described and illustrated.