Genetic variation among Halophila ovalis (Hydrocharitaceae) and closely related seagrass species from the coast of Tamil Nadu, India – an AFLP fingerprint approach

Abstract

Among the seagrass species, Halophila ovalis, H. ovalis subsp. ramamurthiana, H. ovata, H. major and H. minor complex, leaf morphological characters overlap. Previously, plastic and nuclear sequences were successfully applied to resolve genetic variation among all the members within this genus. However, Halophila ovalis, H. ovalis subsp. ramamurthiana and the H. ovata complex have not yet been fully resolved. This leads to the hypothesis that the genetic differences of H. ovalis and H. ovata are not at the loci we were studying. In this study, AFLP analysis based on 49 demes of four Halophila ovalis, one H. ovalis subsp. ramamurthiana and two H. ovata populations collected along the coast of Tamil Nadu, India, were carried out to find the genetic distance within and among populations. Results from a band-based approach showed that H. ovalis and H. ovata are definitely clustered into two clades with 100% bootstrap value. Principal Coordinate Analysis (PCoA) clearly depicts the genetic relationship among the subspecies, lagoon clone and open sea clone of H. ovalis. Results from allele frequency-based approaches including matrix of genetic distances (FST) and AMOVA showed significant differences among populations. Based on the results it is concluded that H. ovalis and H. ovata are distinct species. Halophila ovalis collected at lagoon, estuary and open sea and H. ovalis subsp. ramamurthiana are genetically different.