Progress, problems and patterns in the biogeography of reef corals and other tropical marine organisms

Abstract

This first part of this paper summarizes the descriptive biogeography of reef corals, with mention of other tropical marine organisms, in terms of present-day latitudinal and longitudinal patterns, and stratigraphical patterns (mostly Cainozoic). Present-day generic distributions are well known but species distributions may be a much more complex mosaic than is generally recognized. In particular, further work is needed on geographical population dynamics, possible disjunctions and larval biology. Knowledge of stratigraphical history is currently hindered by insufficient systematic work on Cainozoic corals. The second part reviews current theories for explaining the distribution of reef corals. Biogeographical ideas can be conveniently discussed in terms of a biogeoraphical system in which there are three groups of processes: maintenance, distributional change and origination. These are not necessarily mutually incompatible. There is considerable confusion generated by different meanings of "dispersal" but they can be clarified with respect to this scheme. Maintenance theories are broadly ecological, and, for reef corals, more work is needed to test ideas about distributional dynamics, thermal ecophysiology and effects of georaphical differences in sea water nutrients. Theories of origination and distributional change are largely historical. There are at least thirteen current historical theories for reef corals. These are discussed with respect to the limited amount of empirical analysis that is available. This points to the importance of geotectonic events, and possibly glacio-eustasy, both of which appear to have had considerable influence in the Miocene. Newer ideas reflect a search for testable alternatives to the older idea of an Indo-West Pacific centre of origin. In particular, hypotheses about vicariance amongst oceanic islands, early Cainozoic isolation of Pacific basin regions, late Cainozoic convergence of Indo-Pacific faunas, and vicariance due to a possible land barrier between S. E. Asia and Australia all merit further testing, especially by endemicity analysis, cladistic methods and speciation rate studies. © 1988 Biologische Anstalt Helgoland.