COMMUNITY DYNAMICS OF TROPICAL REEF FISHES - LOCAL PATTERNS BETWEEN LATITUDES

Latitudinal variation in the dynamics of biological communities is amo ng the least addressed and understood topics of modern ecology. Here, I examine the dynamics of coral-reef fish communities inhabiting small rubble patches at 2 locations separated by approximately 9 degrees of latitude (One Tree Island and Lizard Island) on Australia's Great Bar rier Reef. This sampling program ran simultaneously at the 2 locations using identical. census methods, sampled over 16 mo and included 2 su mmer recruitment seasons. Total abundance of all fish species pooled f luctuated seasonally, peaking in summer. Total abundance at sites with in locations differed, but sites at different locations overlapped in abundance. The dynamics of these communities were apparently unrelated to family membership among species, intraspecific abundances or diet. Rank abundances of species present at both locations did not differ, and only a single negative correlation of abundances between species w as detected. Changes in abundance, however, were density dependent. Ma ximum abundance of fishes observed in the first summer explained betwe en 42 and 93% of the variation in subsequent per capita declines in ab undance by the following winter and before recruitment had commenced i n the second year. These density-dependent effects were observed acros s families and across widely separated locations. These results sugges t that the dynamics of these communities were not structured by strong pairwise interspecific interactions, but, instead, may have been stru ctured by some density-dependent process(es) that affected a broad cro ss section of species and that operated irrespective of locality.