ABSTRACT
MARGARET WOHLENBERG MILLER Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric
Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA* * Present address: Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami,
FL 33149, USA
Terrestrial communities display latitudinal gradients in quantitative characteristics such as species diversity while remaining qualitatively similar in structure. For example, both temperate and tropical regions have forests that are composed of canopy trees and understory herbs. Marine hard-bottom communities, in contrast, show qualitative variation in community structure over the latitudinal gradient. In tropical latitudes, scleractinian corals construct coral reefs, one of the most diverse communities on earth. However, scleractinian corals are virtually absent from temperate shallow marine hardbottom communities. Those corals that do occur in temperate habitats are usually solitary, colonial but diminutive in size, or restricted to very deep water (e.g. Squires & Keyes 1967, Schuhmacher & Zibrowius 1985, Cairns 1994). Instead, kelps or other large brown
© A.D.Ansell, R.N.Gibson and Margaret Barnes, Editors
UCL Press
seaweeds are commonly the primary occupiers of space and purveyors of physical structure on shallow temperate reefs (Schiel & Foster 1986). In addition to low temperature, competition from these large seaweeds at high latitudes has been suggested to limit corals and coral reef structures to tropical latitudes (Johannes et al. 1983). While the lack of coral reef development in many tropical habitats indicates that natural local factors within the tropics can also restrict corals (e.g. areas of upwelling or severe river runoff), a general latitudinal pattern of largely disjointed distribution of coral-dominated and plant-dominated community types is evident on a global scale (Fig. 1).
