Distribution and Abundance of Cheilostome Bryozoans on the Caribbean Reefs of Central Panama

Cheilostome distribution and abundance were surveyed on eight reefs along the Caribbean coast of Panama to determine the extent of local variation in community structure. Communities were sampled from two depths, from several different substrata, and from two reef types defined by degree of exposure to terrigenous influence. Communities differed widely in total cheilostome cover, species richness, and species abundance pattern, but none of these measures were consistently related to reef type, depth or substratum. In all samples, a small number of the species present contributed disproportionately to the spatial cover or population of colonies. Multivariate analyses based on species cover or colony abundance distinguished between communities with a high level of accuracy, but with no consistent grouping by depth or reef type. Among the main space-occupying cheilostome species, local abundance patterns reflecting differences in reef type were rare, but several species showed clear depth-related trends in abundance.

Cheilostomes dominating similar reef habitats in Jamaica and Venezuela are often identical or congeneric with those common in Panama, but some widespread species show inconsistencies in habitat preference. Results from Caribbean reefs suggest a general correlation between cheilostome life history and ecological success on different substrata. We suggest that geographic differences in the relative abundance of reef species probably do not result from a high sensitivity to local conditions, but are more likely to have a stochastic and historical basis.