Mangrove floristics of the Andaman and Nicobar Islands: critical review and current scenario

Abstract

The mangroves of the Andaman and Nicobar Islands (ANI) are recognized as the best in the country in terms of density and growth. However, considerable disparities still exist in the species composition and classification of mangrove species in the ANI. Further, taxonomical identity and occurrence of certain mangrove species in the ANI remain imprecise. Considering these facts, the present study was carried out to provide an updated checklist of true mangrove species of the ANI based on the extensive field surveys and perusal of the existing literature. Surveys were carried out in eight regions of the ANI and in each region, specific sites were selected based on representativeness, importance, and accessibility. Altogether, 51 sites were surveyed during 2009–2014. The results show that the mangroves of the ANI consist of 38 true mangrove species belonging to 13 families and 19 genera, which account for about 50 % of the global true mangrove species. The Andaman Islands have 35 and the Nicobar Islands have 21 true mangrove species. Among the eight regions, the mangrove diversity is high in South Andaman, followed by Middle Andaman, Mayabunder, Diglipur, Nicobar, Little Andaman, Havelock, and Baratang. Given their limited geographical area, the high similarity index values between the regions (>0.6) indicate the homogenous nature of mangrove diversity in the ANI and absence of impassable dispersal barriers. The Nicobar region exhibited low similarity with other regions (0.61–0.69). The changes in species numbers compared to earlier studies could mainly be attributed to the lack of extensive field survey in the past. Thus, periodical information on the extent and status of mangroves in the islands is imperative not only to improve our understanding of phytogeography, but also for better management and conservation.