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| Geographic patterns in species richness are mainly based on
wide-ranging species because their larger number of distribution
records has a disproportionate contribution to the species richness
counts. Here we demonstrate how this effect strongly influences our
understanding of what determines species richness. Using both
conventional and spatial regression models, we show that for
sub-Saharan African birds, the apparent role of productivity diminishes
with decreasing range size, whereas the significance of topographic
heterogeneity increases. The relative importance of geometric
constraints from the continental edge is moderate. Our findings
highlight the failure of traditional species richness models to account
for narrow-ranging species that frequently are also threatened. | |
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