Taxonomic studies on the genus Leea L Vitaceae in India

Abstract

The present study deals with the taxonomic revision of the genus Leea L. (Vitaceae) in India. This tropical genus comprises 38 species worldwide restricted to the Indo-Malayan region extending to Australia and some parts of Africa and Madagascar. This study recognized 17 species in India with two endemics, mainly distributed in Northeast India, Peninsular India and Andaman and Nicobar Islands. The genus Leea was earlier recognized at the rank of family, but now included under the subfamily Leeoideae Burmeister of Vitaceae according to the APG system of classification. They are mostly shrubs, trees or creeping herbs, and some species possess prickles on their stems. Leea is distinguished by the presence of a conspicuous petiolar stipule, well-developed floral disc, syngenecious stamens, one ovule in each locule and ruminate endosperm. A combined approach of morphology, anatomy, micromorphology and molecular data were used since for species delimitation in this genus is often quite challenging. An illustrated taxonomic account of the genus has been made and a taxonomic key was also prepared. Two new species have been described from the study area and three names, Leea sundaica Miq., Leea latifolia Wall. ex Kurz, Leea trifoliata M.A.Lawson were reinstated from Leea indica (Burm.f.) Merr., Leea macrophylla Roxb. ex Hornem., and Leea compactiflora Kurz respectively. Leea talbotii King ex Talbot was reduced into the synonymy of Leea setuligera C.B.Clarke and Leea aequata var. villosissima Hochr. was synonymized under Leea aequata L. Lectotypificaton of 41 names were also carried out. The conservation status of all the species was assessed according to the IUCN criteria (Version 15.1, 2022). Among the 17 species, eight species were assessed as Endangered (EN), two species as critically endangered (CR) and seven species as Least Concern (LC). Ex-situ conservations of 50 accessions of 15 species were maintained in Calicut University Botanical Garden (CUBG). The foliar anatomical study of Leea in India was also carried out, and the leaf anatomy of most of these species has never been described before. The result showed that, among the anatomical characters, the number of palisade parenchyma, the thickness of leaves, shapes of adaxial and abaxial surfaces of midrib and rachis, number of vascular bundles in the midrib, types of stomata, outlines of anticlinal walls of epidermal cells, presence of hypodermis, and accessory vascular bundles in the midrib region provide additional information for delimitation of species. An identification key using anatomical characters was also provided to distinguish the specie The seeds in Leea were studied through both light microscopy (LM) and scanning electron microscopy (SEM) to facilitate the identification of species based on seed characters. The seeds are wedge-shaped, triangular in cross-section, endosperm is ruminate with a long or linear dorsal chalaza. Seed coat ornamentation varied among species based on SEM analysis. The palynological studies showed the pollen grains in Leea were stenopalynous and consist of trizonocolporate radially symmetrical isopolar pollen grains. Most of the species have microreticulate exine ornamentation except in two spiny species, Leea angulata Korth. ex Miq. and Leea adwivedica K.Kumar, where it was foveolate type. This is the first phylogenetic study on Indian Leea. The present molecular study based on nrITS showed that the tropical genus Leea is monophyletic and resolved into four major clades in both maximum-likelihood and Bayesian analysis. The clade I consisted of a single species L. asiatica (L.) Ridsdale, having the free stamens. clade II consisted of species with prominent bracts, clade III consisted of species having prominent persistent bracts and the rest of the Indian species were nested in clade IV, which was further resolved into four subclades (a-c). The current work also supports the resurrection of the three species, L. latifolia, L. trifoliata, and L. sundaica and also support the establishment of new species in this genus.