Diversity, recruitment and competition on island shores at south-polar localities compared with lower latitudes: encrusting community examples

Comparisons of temperate and tropical shorts have yielded considerable deba te as to whether the former really are less benign. diverse and structured by different ecological processes. Studies of comparable boulder communitie s have shown high within region variability. Equivalent polar assemblages, from island shores compared here, show much reduced within region variabili ty and considerably reduced numbers of phyla and species encrusting boulder s. The rate of colonisation (compared from settlement panel studies) was an order of magnitude higher in warmer water, but did vary with isolation (ne ar vs offshore islands). Comparison of the most ubiquitous taxon, the bryoz oans, between polar and non polar sites shows a decrease in the proportion of inter-specific competition, indeterminate competitor (species) pairs and incidence of tied outcomes in competition. These three parameters all incr eased with depth at the localities studied, whilst no obvious influence of isolation was found.