Abstract

Major regional and local differences in the composition and structure of shallow-water communities in the Indo-Pacific marine province may be related to differences in nutrient availability. Animals in eutrophic environments tend to be fast-growing, with rapid population turnover and generalist habits. Bivalves, for instance, are much more diverse and abundant in eutrophic ‘continental’ environments, than on oceanic, oligotrophic atolls and reefs. Neogastropods with generalist diets include Babylonia, which are restricted to continental shores, and Nassariidae species, which are much more diverse in eutrophic environments. A comparison of food webs, involving predatory gastropods from oligotrophic and eutrophic environments, shows that the oligotrophic webs are based upon benthic algae and detritus, whilst the eutrophic webs are based upon phytoplankton. There is some evidence that rates of evolutionary diversification may be related to nutrient regimes.

Introduction

The shallow-water biota of the Indo-Pacific marine province is characterised both by the very high species diversity, but also by the very broad geographical ranges of many species, some encompassing the entire area of the province (Kohn, 1983; Kohn & Perron, 1994). Considerable attention has been given to the analysis of the biogeographical patterns and origins of this diversity in relation to plate and local tectonic history, dispersal barriers, habitat diversity, temperature, and so on (Kohn, 1983; Kay, 1984; and general review by Rosen, 1988).