The overlooked complexity of avian brood parasite–host relationships

The interactions between avian brood parasites and their hosts have become widely recognised as model systems for studying coevolutionary processes. These systems have traditionally been viewed as relationships between one species of brood parasite and one species of host; however, with most brood parasites being known to parasitise multiple species of host and hosts often being subject to parasitism by multiple brood parasite species, opportunities to examine the ecology and evolution of multispecies interactions have generally been overlooked. Here, we compile data on all known brood parasite–host relationships and investigate where and how multiple species of brood parasites and hosts coexist. Considering these relationships as interactions in ecological networks, we find that complex brood parasite–host systems (i.e. those that include multiple species of brood parasites and hosts) exhibiting highly connected networks are found globally, with increased prevalence at lower latitudes ...