Environmental variation in a fossil scleractinian coral

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Abstract
Sample populations of Solenastrea fairbanksi, collected from different environments in the Pliocene Imperial Formation, can be distinguished by measurements of linear dimensions of the coenosteum and thickness of septal structures. In these characters, magnitudes of intercolony variance components are lower than interpopulation or intracolony components, suggesting that the variation is largely caused by environmental factors. Three patterns of mean variation exist between populations: highest means occur in shallow, offshore (high energy) environments; highest means occur in shallow environments with low turbidity (high light intensity); and highest means occur in clear, deeper offshore environments (favorable nutrient supply). The distance between adjacent corallites and the inverse of coenosteal porosity follow the 1st pattern, measures of thickness of vertical corallite structures follow the 2nd, whereas estimates of annual growth rate follow the 3rd. Corallite diameters and columella thicknesses do not vary between populations. Comparisons with modern species [Montastraea annularis and Siderastrea siderea] show that many characters in S. fairbanksi respond to environmental factors in a manner different from similar characters in other scleractinian species. In fact, inflexible characters in S. fairbanksi are highly flexible in other species.