COMPETITION IN ENCRUSTING ANTARCTIC BRYOZOAN ASSEMBLAGES - OUTCOMES, INFLUENCES AND IMPLICATIONS

Over 4000 bryozoan-bryozoan interactions were recorded from a total of 985 rocks from six locations at Signy Island in the maritime Antarcti c. The majority of these interactions were interspecific meetings. The identity of the competitive species was a major influence on the outc ome of encounters, whereas depth and surface area of rocks had little significant influence. The assemblage of bryozoans could be ranked int o a clear hierarchy with a competitively dominant species. Zooidal hei ght and colony growth morphology were found to be important factors in overall overgrowth rank. Few interspecific encounters resulted in ind eterminate outcomes, but a tied outcome was found to be most likely be tween competitors of similar overgrowth rank. In contrast, intraspecif ic meetings mostly resulted in tied outcomes. Species with a higher pr oportion of colonies on the upper surfaces of rocks were found to have a lower incidence of tied outcomes. One explanation may be the potent ially more successful larval dispersal on upper rock surfaces in highe r water flow, and the resulting decreased likelihood of neighbours bei ng related. Several incidences of homosyndrome were also observed in t hree bryozoan species.