Ecoimmunity in Darwin's finches: invasive parasites trigger acquired immunity in the medium ground finch (Geospiza fortis)

Invasive parasites pose a serious threat to native animal populations, because hosts with no history of exposure may lack effective immune defenses. Invasive parasites are a particular threat to small, island populations [1,2]. For example, introduced malaria (Plasmodium relictum) has exacerbated the decline of Hawaiian honeycreeper species, many of which are now extinct [3,4]. Darwin's finches have recently been exposed to two introduced parasites of high conservation priority: avian pox virus (Poxvirus avium) and the nest fly Philornis downsi (Figure 1A, 1B) [1,2].