While some taxonomic groups like protozoa and certain helminths show greater parasite richness in the tropics, other host-parasite systems exhibit reverse gradients or no clear latitudinal pattern at all, making the claim contested.
The retrieved literature shows mixed support for the claim that parasite diversity peaks in the tropics. Some studies (e.g., [0], [2]) confirm a traditional latitudinal diversity gradient for specific groups like protozoa in primates or nematodes in rodents. However, other studies find reverse latitudinal gradients ([6]) or caution that data gaps, sampling bias, and different taxonomic groups (such as cestodes, trematodes, or fish helminths) undermine a universal rule for parasites ([8]). Therefore, the balance of evidence is contested.