Coral reef fish assemblages: contribution of stochastic effects on variation declines over time.
Waltho, Nigel*,1, Kolasa, Jurek1, 1 McMaster University, Hamilton, ON
ABSTRACT- Assemblages of coral reef fish are highly variable in space and time. Various stochastic models have been proposed to explain this variability; some rely on a single process, and others rely on and partition the variability among several processes (lottery, recruitment limitation, others). Recent work however suggests that habitat structure - patch size, spatial configuration, and architectural complexity - may constrain the influence of these stochastic processes, and further, these effects may be species-specific. We hypothesized that inclusion of habitat structure in analyses of temporal patterns will account for much of assemblage variance hitherto attributed to stochastic processes. We monitored fish assemblage (Stotal=60 species) on 40 patch reefs 6 times between 1994 and 2005, in Discovery Bay, Jamaica. We used the Mantel test of matrix similarity (Bray-Curtis rank similarity) to detect patterns of seriation, that is adjacent date similarity, at three habitat scales: individual reef, random landscapes of 20 patch reefs, and the full landscape of 40 reefs. At the scale of the individual reef we detected no systematic pattern of seriation; nevertheless seriation value did increase with patch size (r2 = 0.257, P< .001). At the scale of the randomly chosen 20-reef landscapes we detected no seriation. At the scale of the entire landscape of 40 patch reef we found strong seriation, and that the seriation patterns were primarily produced and maintained by the six most common species. We found no patterns of seriation using 52 rare species. These results suggest that coral reef assemblages retain a core structure that appears much more robust over long-term than a short-term analysis of the whole assemblage might reveal.
Key words: coral reefs, fish, stochastic, habitat structure
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