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| We investigate the relative importance of stochastic and
environmental/topographic effects on the occurrence of avian centres of
endemism, evaluating their potential historical importance for
broad-scale patterns in species richness across Sub-Saharan Africa.
Because species-rich areas are more likely to be centres of endemism by
chance alone, we test two null models: Model 1 calculates expected
patterns of endemism using a random draw from the occurrence records of
the continental assemblage, whereas Model 2 additionally implements the
potential role of geometric constraints. Since Model 1 yields better
quantitative predictions we use it to identify centres of endemism
controlled for richness. Altitudinal range and low seasonality emerge
as core environmental predictors for these areas, which contain
unusually high species richness compared to other parts of sub-Saharan
Africa, even when controlled for environmental differences. This result
supports the idea that centres of endemism may represent areas of
special evolutionary history, probably as centres of diversification. | |
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