, Volume 3, Issue 1, pp 43-50

The molluscan fauna of Chagos (Indian Ocean) and an analysis of its broad distribution patterns

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Abstract

A detailed survey of molluscs in the Chagos Archipelago was made (1) to determine whether this isolated atoll group has a diverse fauna, and (2) to identify broad-scale distribution patterns of molluscs in relation to depth, exposure and substrate type: 384 confirmed species (including 282 gastropods and 99 bivalves) compares with reported diversities from other island and continental reef areas, suggesting that Chagos is not depauperate. Molluscs were sampled from 18 zones, which encompassed all habitats to 40 m deep. Cluster analysis based on species similarity revealed 4 main groups from hard substrate and 1 from soft substrate. On hard substrate, depth or depth-related parameters were a stronger determinant of molluscan distribution than seaward or lagoonal position, and greatest diversity occurred between 10–20 m deep on reefs of all exposures.