Competitive Strategies Between Palythoa Caribaeorum and Zoanthus Sociatus (Cnidaria: Anthozoa) at a Reef Flat Environment in Venezuela
The competitive interactions and recolonization processes of two Caribbean zoanthids, Palythoa caribaeorum and Zoanthus sociatus, were studied in the field. Their competitive abilities (i.e., overgrowth capacity or growth inhibition) were evaluated by means of periodical observations of naturally occurring contact margins in 64-cm2 non-disturbed areas. Recolonization and growth rates were assessed through experimental removal (64-cm2 clearings) of different proportions of the zoanthid's initial cover of both species. Interactions were observed during 8 months, whereas a 10-month period was allowed for recolonization. Results showed that contact margins between both species remained unchanged along time, suggesting that stand-off or growth inhibition was the main strategy used. For the removal experiments, the initial proportion cleared for each species within the experimental patches was important for the final cover achieved. For P. caribaeorum, the greater the initial cover removed, the greater the final cover achieved. This tendency was not as evident for Z. sociatus. Growth rates were highly variable, ranging from 0.08 ± 0.20 to 0.12 ± 0.06 cm2˙cm border-1˙month-1 for P. caribaeorum, and from 0.05 ± 0.15 to 0.14 ± 0.51 cm2˙cm border-1˙month-1 for Z. sociatus. In general, we found a reduction of the growth rates through time, and P. caribaeorum exhibits a faster initial growth rate. Because the kind of disturbance applied in this study (cover removal) did not favor Z. sociatus, considered as a weaker competitor compared to P. caribaeorum, another compensatory mechanism that allows the coexistence of these species in this reef platform must exist. Several alternatives are proposed. The importance attributed to disturbances as a mechanism that explains the coexistence of species was not evident in our study, providing the disturbance intensity (patch size and proportion of initial cover removed) did not exceed that tested.
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Document Type: Research Article
Publication date: 1996-11-01
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