Species diversity and distribution of mangroves in Andaman and Nicobar Islands, India

Despite extensive studies on mangrove ecosys - tems of Andaman and Nicobar Islands since the 1870s, knowledge of exact species composition is far from com- plete, and there is a lack of comprehensive locality data. The present study was designed to review the existing literature and to provide an updated checklist of the true mangrove species of the Islands. Preliminary surveys were carried out in seven regions (four from the Andaman group and three from the Nicobar group), and the specific survey sites for detailed study (n = 51) were selected based on representativeness, importance, and accessibility. Dur- ing 2009-2013, all the selected sites were visited, and mangrove species occurrence was recorded. At present, 25 true mangrove species distributed among 10 families and 14 genera were identified vis-a-vis 17 to 36 species reported in earlier studies. The discernible changes in species num- bers from earlier studies could mainly be attributed to our exclusion of associated littoral vegetation and of species unlikely to be present among the true mangroves of the Islands. Given their limited geographical area, the low similarity index values between the Andaman and Nico- bar Island groups ( ≤ 0.4) indicate a need for periodical surveys, as mangrove biodiversity is usually homogenous in regions where there are no impassable dispersal barri- ers. Further, regular updating of 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.