Why do parasites exhibit reverse latitudinal diversity gradients? Testing the roles of host diversity, habitat, and climate

Aim: The latitudinal diversity gradient (LDG) – in which species richness decreases from the equator toward the poles – is among the most fundamental distributional patterns in ecology. Despite the expectation that the diversity of parasites tracks that of their hosts, available evidence suggests that many parasites exhibit reverse latitudinal gradients or no pattern, yet the rarity of large-scale datasets on host-parasite interactions calls into question the robustness of such trends. Here, we collected parasitological data from a host group of conservation importance – lentic-breeding amphibians – to characterize the form and direction of relationships among latitude, parasite richness, and parasite load.

Location: The contiguous USA. Time period: 2000 to 2014.

Major taxa studied: Lentic-breeding frogs and toads and their helminth parasites.

Methods: We collected information on parasite richness and infection load for 846 amphibian populations representing 31 species. We comb...