Similarity and dispersal in a neutral model with nonsympatric speciation

Mean Bray-Curtis similarity index between communities with different values of $\sigma$, the variance of the dispersal kernel, in a neutral model with allopatric and parapatric speciation. When $\sigma$ is small, the communities are so isolated that, after a series of allopatric and parapatric speciation events, they will reach a unique composition (thus a Bray-Curtis index of 0). When $\sigma$ is large, the level of gene flow prevents speciation and the entire metacommunity is dominated by a single species (thus a Bray-Curtis index of 1).

To do: more results in the $0.04 < \sigma < 0.12$ range to get a smoother curve :P

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