Genetic diversity and population structure of the mangrove lime (Merope angulata) in India revealed by AFLP and ISSR markers

Abstract

The mangrove lime, Merope angulata (Willd.) Swingle (Rutaceae) is a threatened mangrove associate species occurring sporadically in the tidal forests from Papua New Guinea to the east coast of India. It is an underutilized salt tolerant plant related to Citrus. We have applied AFLP and ISSR markers to estimate the extent of genetic diversity among 55 individuals of M. angulata, sampled from two natural populations (Bhitarkanika Wildlife Sanctuary) and one ex situ population (Jharkhali Mangrove Ecological Garden) in India. A combined analysis of both AFLP and ISSR markers revealed low polymorphism (42.93%) and a moderate heterozygosity and Shannon diversity index (H=0.393, I=0.571) in the species. The Jaccard genetic distance among 55 accessions ranged from 0.16 to 0.74 (average 0.43). Analysis of population genetic structure using Bayesian method in STRUCTURE software identified two genetic clusters. FST statistics and AMOVA results indicated low population differentiation with high gene flow. Haplotype indices and mismatch distributions indicated some evidence of expansion in the two natural populations. Outcrossing test revealed a predominantly out-breeding system with high outcrossing rate. The high gene flow detected among the populations indicates that M. angulata does not face any genetic drift, and hence no local genetic differentiation and population divergence. The highly fragmented state of its habitats warrants adequate measures for maintenance of genetic diversity in this species without further depletion. This is the first report on molecular analysis of genetic diversity and population structure of M. angulata from its native distributional range in India.