Taxonomy and Systematic Analysis of the Two Genera Alpinia and Amomum of the Family Zingiberaceae in Sri Lanka

Abstract

Alpinia and Amomum are the largest two genera that list the highest number of endemics offamily Zingiberaceae in Sri Lanka. The family is recognized as a least studied plant group inthe country, justifying the need for a thorough study. Hence, it is timely that the family istaken into consideration of molecular and systematic studies given new techniques areavailable. As a pioneering step, in this study, we addressed several taxonomic issues,phylogenetic relationships and conservational status of Alpinia and Amomum. In order tocollect more morphological data to address species boundaries with better insights, over 130morphological characters were studied and analysed using multivariate statistical methods.Molecular phylogenetic analysis was done using two Chloroplast gene regions (trnL-trnF andtrnS-trnfM). Results of the morphological analysis revealed the segregation of species ratherdepending on both vegetative and floral characters than only on floral characters. Study alsoidentified a group of Amomum with a new character combination which needs to berecognized as a new species or subspecies along with a new addition to genus Alpinia (A.zerumbet) in Sri Lanka. Furthermore, in our efforts to make a field key for easy identificationof species, results of this study also highlighted the difficulty in using only vegetativecharacters to differentiate species. Hence, the study has resulted in identifying a different andan easy set of morphological characters for species identification for Sri Lankan species.Evolutionary analysis of the two genera confirms that the Sri Lankan members of the twogenera Alpinia and Amomum have a monophyletic origin. Although the genus Alpinia has amonophyletic lineage, two members (A. abundiflora and A. fax) show a polytomy within thegenus. This was evident in both phylogenetic analysis and the morphological analysis.According to trnL-trnF and trnS-trnƒM data analysis, all the studied members of the genusAmomum have an exclusive monophyletic origin. Illumination of an immediate need forconservation efforts of these species is another important finding of the current study.