FERRELL, DAVID/L; Florida State University: Clonal diversity and agonistic capabilities of the aggregating anemone Anthopleura elegantissima in Barkley Sound, British Columbia

The sea anemone Anthopleura elegantissima, a common inhabitant of northeastern Pacific intertidal environments, proliferates via longitudinal binary fission, thereby generating clonal aggregations. Conspecific encounters result in agonistic interactions in which specialized defensive tentacles, or acrorhagi, are employed. Differences in agonistic capabilities are identified via the outcomes of experimental assays between pairs of individual anemones. Despite intense competition for space, apparently competitively inferior clones persist in natural populations. The presence of substantial clonal diversity and variation in competitive ability is problematical, however, only if experimental assays accurately reflect interactions between entire aggregations, as they occur in nature. I explored the spatial distribution and agonistic capabilities of 168 A. elegantissima clones distributed throughout Barkley Sound, British Columbia, to evaluate the premise that seemingly competitively dominant clones, as identified by greater acrorhagial allocation, actually dominate in natural interactions between entire aggregations. I tested three observational predictions that are consistent with this premise. First, presumably dominant clones should form larger aggregations, on average, as a result of their ability to outcompete neighboring conspecifics. Second, dominant competitors should be increasingly abundant in environments with greater intraspecific competitive intensity. Third, neighboring clones should be of roughly equivalent competitive ability; otherwise, such interactions would proceed to competitive elimination. These results may help in understanding possible mechanisms for maintaining clonal diversity in A. elegantissima.