Many recent studies proposed a ‘dilution effect hypothesis’ that species diversity can reduce disease risk. This hypothesis presents an exciting convergence of public health concern and conservation, and has attracted much attention. However, the uncertainty persists over its mechanisms and generality.
In this thesis I tested the dilution effect hypothesis and explored its generality and mechanisms. I first detected a dilution effect of mammal species richness on the disease risk of bovine tuberculosis in Africa. Then, I found high quality species for pathogens are more resistant to biodiversity decline in communities, which could act as a possible mechanism for the dilution effect. Finally, I found that either a negative or a positive relationship of species richness with disease risk can be detected in fragmented landscape. This thesis contributes to a better understanding of species richness on disease risk and the generality of the dilution effect.