Migratory birds shape potential haemosporidian transmission through a parasite-sharing network

Migration is one typical behavior that can affect parasite composition and transmission in local host communities, as migratory hosts are often heavily infected and may serve as a ‘vehicle’ to transmit parasites to new hosts. Therefore, understanding how local parasite transmission is shaped by these highly connected visitors is critical for guiding disease prevention. However, this endeavor is largely hampered by the difficulties of observing transmission processes, especially in natural host-parasite systems. Regarding that, network analysis may provide additional insights to infer cross-species transmission and help identify the reservoir host species. Here, by using a bird-haemosporidian system in the Thousand Island Lake, China, we generated parasite-sharing networks to investigate how migratory hosts may influence sharing patterns and, in turn, the potential transmission in local bird communities. We evaluated the network centrality of migratory birds and assessed the relative importance of host functional traits and phylogenetic relatedness in structuring the propensity of parasite sharing. We found that migratory species significantly shaped the overall network structure by bridging distinct modules though they exhibited no superior importance than resident birds when referring to node centrality. Moreover, we found that node centrality and the extent of parasite sharing of hosts are mainly predicted by host functional traits, while host phylogenetic relationships played a relatively minor role. Our findings highlight the vital role of migratory birds on parasite sharing in local communities and suggest that host functional traits could be key drivers of potential cross-species transmission.