Taxonomic study of Melastoma L. in Peninsular Malaysia

Abstract

Species identification based on hypanthium structure and herbarium samples were insufficient for Melastoma. Melastoma flowers are very delicate and tend to become incomplete specimens. Therefore, it is impossible to rely solely on flower characteristics and herbarium samples for the identification process. Hence, a comprehensive study was set up to identify varietal differences among Melastoma species found in Peninsular Malaysia. Our objectives can be restated as follows 1) to identify and describe the morphological characteristics of Melastoma species, 2) to identify and describe the anatomical and micromorphological characteristics of Melastoma species and 3) to identify and characterize the gene of Melastoma species. A total of 26 Melastoma accession were collected and given a final of 87 vegetative structures and 144 reproductive structures. This study has identified hypanthium, leaf, and twigs indumentum as important morphological structures for species identification. Meanwhile, 54 anatomical characters were identified and recorded among 20 selected taxa. Besides, 15 types of trichomes were determined to serve as supporting characters for Melastoma in the absence of reproductive structure. DNA analysis conducted on 11 selected taxa of Melastoma were subjected to DNA extraction, PCR with four new primers (triosephosphate isomerase (tpi) gene, photosystem II protein D1, partial cds; chloroplast (psbA) gene, granule-bound starch synthase (gbss) gene and vacuolar invertase (vr) gene), and DNA sequencing to obtain the final result. Nevertheless, only the tpi genes showed a promising result with convincing bootstrap support in the phylogenetic study. Of the eleven taxa, nine proved to be distinct species based on genetic characters. In conclusion, this study identified 14 taxa and seven M. malabathricum accessions. Out of 14 taxa, 6 were newly described, and three were reinstatement as species. These results reinforce the hypothesis that morphological structure will be the most important source of information for the identification of Melastoma.