Prominent hallmarks of the widely distributed, mainly tropical marine snail genus Conus are: (1) its unusually high species diversity; it is the largest genus of animals in the sea, with more than 800 recognized species; and (2) its specialized feeding behavior of overcoming prey by injection with potent neurotoxic, paralytic venoms, and swallowing the victim whole. Including the first report of a human fatality from a Conus sting nearly 350 years ago, at least 141 human envenomations have been recorded, of which 36 were fatal. Most Conus species are quite specialized predators that can be classified in one of three major feeding guilds: they prey exclusively or nearly so on worms, primarily polychaete annelids, other gastropods, sometimes including other Conus species, or fishes. These differences are shown to relate to the severity of human envenomations, with the danger increasing generally in the order listed above and a strong likelihood that all of the known human fatalities may be attributable solely to the single piscivorous species C. geographus.

Extrinsic and intrinsic factors, physical and biological factors, and the interactions of all these are hypothesised to affect the diversity of coral reef-associated faunas. Extrinsic factors include environmental change at large spatial (regional) and temporal (geological) scales, and small (local or landscape) scale variation over ecologically relevant time. The latter also impinge on aspects intrinsic to the organisms, e.g. ecological specialisation, key innovations and life-history attributes, especially larval biology of sedentary benthic invertebrates. Certain species-rich genera and families of invertebrates and fishes contribute importantly to high species diversity of Indo-Pacific coral reefs. Naturally occurring gradients in diversity, ecology and life-history within these taxa can serve as dependent variables to test hypotheses of diversification. Gradient analyses of the most diverse genus of Indo-Pacific reef invertebrates, the gastropod Conus, support the ecological determinism and life-history hypotheses of diversity. The data do not refute other hypothesised mechanisms, which probably also operate. Broader application of gradient analysis to diverse taxa in the future may sharpen understanding of processes leading to modern patterns of diversity. Introduction Although geographically restricted to tropical seas and occupying only 0.1% of the earth's surface, coral reefs have globally important implications for marine biodiversity. Reefs support unusually diverse animal communities with distinctive taxonomic structure and geographical distribution patterns. Coral reefs are oases of high primary productivity in barren tropical seas, and reef-building organisms have changed the face of the earth by creating entire archipelagoes of islands and, over geological time, landforms that have become incorporated in continents.

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