Variation in immunity and health in response to introduced avian malaria in an endemic Hawaiian songbird

International audienceEmerging infectious diseases are spreading at unprecedented rates and affectingwildlife worldwide, with particularly strong effects on islands. Since the introductionof avian malaria to Hawaii a century ago, the disease has contributed to thedecline and extinction of several endemic Hawaiian honeycreeper species. At lowelevation, where avian malaria is prevalent, Hawaii Amakihi Chlorodrepanis virenshoneycreeper populations have experienced strong selection by the disease andhave evolved increased malaria resilience, the ability to recover from infection.The goals of this study were to describe malaria infection rates across HawaiiIsland, to examine the role of innate immunity in malaria resilience, and to determinethe effects of resilience and chronic infection on Amakihi health. We measuredmalaria infection and metrics of innate immunity and health in low elevationAmakihi populations, which are more resilient to malaria, and high elevation populations,which have experienced weak malaria selection and are less resilient tomalaria. Avian malaria infection was higher at low than high elevation. Measuresof innate immunity were higher in low than high elevation Amakihi, but alsodepended on whether the birds were from the leeward side of the island (low rainfall)or windward side of the island (high rainfall) and whether they were freelivingor captive. Regarding measures of health, body condition was better inmalaria-infected than uninfected Amakihi, while hematocrit did not vary by malariainfection but was higher in high than low elevation birds. These are among thefirst results to describe variation in immunity and health according to avian malariaselection and infection in Hawaiian honeycreepers. Understanding the impacts ofintroduced diseases on island species, which are particularly susceptible to novelpathogens, will provide critical insight into how introduced disease may affectendangered species