Abstract
The Theory of Island Biogeography yielded the important idea that species richness within sites should depend on site connectivity, i.e. its connection with surrounding potential sources of immigrants. However, the effect of connectivity on species presence and community richness in empirical studies is often quite limited, partly because classic indices used to quantify connectivity (e.g. distance to nearest habitat patch) need improvement. Current methodological advances for quantifying connectivity lie along three directions: building better indices that more carefully trace potential fluxes of individual between habitat units, combining such indices and searching for the most appropriate way of describing habitat spatial distribution, using patches or cells as elementary units. Here we assessed the potential of 63 contemporary connectivity indices that explore these different tracks by applying them to virtual habitat maps with contrasted habitat amount and configuration coupled with a neutral metacommunity model. We found that choosing buffers indices (and more generally flux indices computed using habitat cells) is the most fruitful methodological choice to improve the explanation of species richness. Refining the scaling of flux indices could bring an additional improvement although quite limited. Combining indices of different type (connector and flux) also marginally improved the ability to explain species richness. In line with the habitat amount hypothesis, our results suggest that buffer connectivity indices are a simple and robust approach that may prove sufficient for capturing connectivity effects in many contexts, potentially leading to very strong effect sizes upon community richness.
