Novel Phylogeographic Structure of Avian Haemosporidians in a Widely Distributed Host

Avian haemosporidian parasites are responsible for avian malaria and related blood diseases, which may cause harm to various hosts. Understanding the environmental factors that affect host‒parasite associations is critical for public health. However, most studies of this topic to date have focused on pooled data from communities, while the different traits of different host species often lead to an underestimation of these factors. In this study, we investigated the phylogeographical pattern of haemosporidian parasites in a widely distributed resident bird, the Eurasian tree sparrow (Passer montanus), as well as the impact of environmental factors, including latitude, annual temperature, and humidity, on their prevalence. We observed that the prevalence of these parasites varies across sites but is generally low. Despite that, different patterns were observed for the different parasite genera. Plasmodium lineages are more widely distributed, whereas Haemoproteus are restricted to sites at lower latitudes and with lower annual temperatures, coincident with the barrier of the Yangzi River in China. This study highlights the importance of focusing on a single host when investigating variation in host‒parasite associations.