Taxonomic Revision of the Genus Pavetta (Rubiaceae) in Indian Sub-Continent

Abstract

Taxonomic revision of the genus PAVETTA(Rubiaceae) in Indian subcontinent results in recognition of 25 species and 8 extratypical varieties. 13 species and 6 varieties described earlier are reduced to synonyms, and 5 species reduced to varietal rank. Two new combinations (P. indica var. glabrescens (Kurz) Deb & Rout and P. minor (Hook.f.) Deb & Rout) have been published. Dichotomous keys have been prepared for identification of taxa of all levels. Critical notes on nomenclature, morphological characters etc. have been provided after description of species wherever necessary. Morphological characters have been studied thoroughly. Special attention has been given on characters like indumentum, colleters, domatia, bacterial leaf-galls, pollen, seed coat, corolla microcharacters etc. The anatomical characters (internode, node, petiole and leaf) of P. indica have been studied. Information available in literature on wood anatomy, chromosome numbers and pollen nuclear numbers have been incorporated.

Morphology of indumentum and bacterial leaf-galls have been studied in all taxa. Colleters have been studied in 28 taxa; domatia found in 13 taxa. Microcharacters of outer surface of corolla tube (8 taxa) and inner surface of corolla lobes (19 taxa) have been studied under SEM in magnification up to 3200. Pollen morphology have been studied both in LM (27 taxa) and SEM (16 taxa). Seed coat morphology has been studied in cross section under compound microscope (13 taxa) and surface under SEM (10 taxa).

Of the species studied, 16 are distributed in India extending to adjoining region, 3 in Myanmar, Bhutan and Bangladesh and 9 species in Sri Lanka. P. indica is most widely distributed, almost throughout the country and extends to its adjoining region ; P. bimahica is endemic to Myanmar; six species are endemic to Tamil Nadu (Nilgiri and hills), Kerala and Andhra Pradesh and one species is distributed in Andaman and Nicobar Islands.