Energy input, habitat heterogeneity, and host specificity on avian haemosporidian diversity at continental scales

The correct identification of biotic and abiotic drivers affecting parasite diversity and assemblage composition at different spatial scales is crucial for understanding how pathogen distribution responds to anthropogenic disturbance and climate change. Here, we used a database of avian haemosporidian parasites to identify such drivers and their effect on the taxonomic and phylogenetic diversity of genera Plasmodium, Haemoproteus, and Leucocytozoon from three zoogeographic regions. We explored how parasite diversity is related to energy input (i.e., temperature, precipitation, and potential evapotranspiration [PET]), to habitat heterogeneity (i.e., climatic seasonality, vegetation density, ecosystem heterogeneity, human disturbance, and host richness), and to a novel assemblage-level metric related to parasite niche overlap (degree of generalism). We found that the relative importance of the predictors differed between the three studied parasite genera and across diversity metrics. Among the most consistent predictors, host richness was positively related to the taxonomic diversity of the three genera. Energy input and human footprint explained the phylogenetic diversity of Haemoproteus. Finally, the degree of generalism explained the diversity of Plasmodium and Leucocytozoon. Our results suggest that different dimensions of haemosporidian diversity are shaped by energy input, host heterogeneity, and assembly processes related to parasite resource use within local parasite assemblages.