Community assembly in Lake Tanganyika cichlid fish: quantifying the contributions of both niche-based and neutral processes.

Bray–Curtis dissimilarity of communities simulated using STEPCAM in the absence of niche‐based processes also correlated significantly with normalized environmental distance, but had a much lower R 2 value (Figure 3 , right panel, R 2 = .11, Mantel test, Mantel‐ r statistic = .335, p = .00001, 100,000 permutations), and a significantly lower slope (slope for empirical communities: 0.43, for simulated communities: 0.07, ANCOVA, p < 2e‐16), indicating that environmental variation has a highly significant effect on community composition. 3.2 Contributions of different community assembly processes Fitting STEPCAM to the trait distributions of the 36 different transects yielded an average contribution of stochastic assembly steps of 72%, an average contribution of habitat filtering steps of 9%, and an average contribution of limiting similarity steps of 19% (Figure 4 ).

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