Diversity of coral reef fish assemblages: Modelling of the species richness spectra from multi-scale environmental variables in the Tuamotu Archipelago (French Polynesia)

Ten atolls of contrasting morphology and low human pressure were investigated in the Tuamotu Archipelago (French Polynesia) during the research program “Typatoll”. This program produced large data sets about species richness of undisturbed fish assemblages and environmental data recorded at three spatial scales. Multivariate analyses defined six groups of transects of similar multi-scale environmental characteristics. Smoothed histograms (spectra) of species richness were plotted for each group of transect according to six size classes, six diet classes and six life-history classes of fish assemblages. The shape of spectra among groups of transects was then modelled through a single equation, determined by goodness-of-fit techniques. The height of each spectrum was then predicted by General Linear Model. Kolmogorov–Smirnov tests showed no significant difference between predicted and observed distributions of species richness. This two-phase model allowed predicting the diversity structure of undisturbed reef fish assemblages from few environmental data for the first time in the Pacific region. The resulting model will provide an efficient tool for detecting anthropogenic effects on the diversity of reef fish assemblages in atolls of the archipelago. This modelling approach could be adapted to provide a tool for the evaluation of variables affecting diversity of coral reef fish assemblages whatever the habitat they live in, and more generally the diversity of any other highly diversified tropical communities.