Latitudinal gradients of parasite richness: a review and new insights from helminths of cricetid rodents

The latitudinal diversity gradient (LDG), or the trend of higher species richness at lower latitudes, has been well documented in multiple groups of free‐living organisms. Investigations of the LDG in parasitic organisms are comparatively scarce. Here, I investigated latitudinal patterns of parasite diversity by reviewing published studies and by conducting a novel investigation of the LDG of helminths (parasitic nematodes, trematodes, and cestodes) of cricetid rodents (Rodentia: Cricetidae). Using host‐parasite records from 175 parasite communities and 60 host species, I tested for the presence and direction of a latitudinal pattern of helminth richness. Additionally, I examined four abiotic factors (mean annual temperature, annual precipitation, annual temperature range, and annual precipitation range) and two biotic variables (host body mass and host diet) as potential correlates of parasite richness. The analyses were performed with and without phylogenetic comparative methods, as n...