GENOTYPIC VARIATION AND CLONAL STRUCTURE IN CORAL POPULATIONS WITH DIFFERENT DISTURBANCE HISTORIES

Genotypic diversity in six populations of the endemic Hawaiian reef co ral, Porites compressa, was directly related to habitat-disturbance hi story. The highest diversity (lowest amount of clonal proliferation) w as found in populations that had been intensely or recently disturbed. In these populations, space was not limited and mean colony size was small (< 500 cm(2)), suggesting early stages of recolonization. In an undisturbed, protected habitat, lower genotypic diversity was a result of a significant degree of clonal replication of established genotype s. Unoccupied substratum was rare in this habitat, and average colony size was large (> 2500 cm(2)). Populations in intermediately disturbed habitats showed intermediate levels of diversity and clonal structure as a result of the combined contributions of sexual and asexual repro duction. Individual clones were distributed over small areas (< 4 m(2) ) or distances (< 1 m) in young populations, and more broadly (> 256 m (2)) and over longer distances (> 90 m) in the older, undisturbed popu lation. Interpretations of life-history parameters and estimates of to tal genetic variability in species that have the potential to reproduc e asexually are dependent upon an assessment of the overall clonal str ucture of populations. The power of genotypic assays to reliably detec t clonal versus unique colonies, as well as the spatial scales over wh ich clonal populations are sampled, are critical to such assessments.