|
| The causes of variation in animal species richness at large spatial scales are intensively debated. Here, we
examine whether the diversity of food plants, contemporary climate and energy, or habitat heterogeneity
determine species richness patterns of avian frugivores across sub-Saharan Africa. Path models indicate
that species richness of Ficus (their fruits being one of the major food resources for frugivores in the tropics)
has the strongest direct effect on richness of avian frugivores, whereas the influences of variables related to
water–energy and habitat heterogeneity are mainly indirect. The importance of Ficus richness for richness
of avian frugivores diminishes with decreasing specialization of birds on fruit eating, but is retained when
accounting for spatial autocorrelation. We suggest that a positive relationship between food plant and
frugivore species richness could result from niche assembly mechanisms (e.g. coevolutionary adaptations
to fruit size, fruit colour or vertical stratification of fruit presentation) or, alternatively, from stochastic
speciation–extinction processes. In any case, the close relationship between species richness of Ficus and
avian frugivores suggests that figs are keystone resources for animal consumers, even at continental scales. | |
|