Mangrove biogeography of the Indo-pacific

Abstract

Studies on biogeography are useful to understand the present and past distribution patterns of biological diversity and their underlying environmental and historical causes. The mangrove realm, largely confined to sheltered tropical and subtropical coastlines within latitudes of around 32°N and 38°S, is divided longitudinally into an Atlantic realm and an Indo-Pacific realm. Because of the relatively recent closure of the Central American Isthmus, a small incursion of the Atlantic realm species has occurred into the Indo-Pacific realm along the tropical and subtropical American Pacific coast and spread north and south since the last glaciation. Although the biogeography of mangroves has been widely discussed, recent investigations of mangrove floristics and genetic diversity using molecular studies warrant a further comprehensive account of the biogeography of mangroves. Considering these facts, the biogeography of the Indo-West Pacific (IWP) mangroves has been examined in detail, and the Atlantic East Pacific mangrove region (AEP) has only been briefly discussed. The difference in species richness between the IWP and the AEP is evidence of the effectiveness of the African land mass and the East Pacific Ocean barriers. Within the IWP, two trends in relation to mangrove species richness can be identified: first, maximal species richness which occurs along the shorelines of Makassar Strait, between Borneo and Sulawesi in Indonesia, and second, the marked attenuation of species numbers with increasing latitude generally related to limiting temperatures. The contemporary and historical processes leading to these trends are summarized and discussed. Finally, the threats to the mangroves of the various regions within the IWP are subsequently briefly reviewed, and given the ecological and economic values of mangroves, the potential of mangrove restoration/rehabilitation to offset mangrove losses is also evaluated.