Meeting Abstract
Invasive species are among the greatest contributors to modern animal extinction. In particular, diseases are invading novel habitats and hosts at unprecedented rates. Avian malaria, introduced to Hawaii in the early 1900s, has contributed to declines of numerous Hawaiian honeycreeper species. The Hawaii Amakihi (Hemignathus virens) is the only honeycreeper that has maintained stable populations at low elevations (< 700m), where avian malaria is prevalent. Evidence suggests that low elevation Amakihi populations have evolved tolerance to malaria, but the mechanisms responsible for this tolerance remain unknown. We hypothesized that immunomodulatory hormones play a role in tolerance to avian malaria, thus predicting that hormone levels would differ between low elevation (malaria-exposed) and high elevation (malaria-unexposed) Amakihi. We measured three immunomodulatory hormones, corticosterone (CORT), testosterone (T), and prolactin (PRL), in Amakihi living at low and high elevations. While baseline CORT was consistent across elevation (p = 0.80), peak CORT (in response to restraint) was significantly greater in high compared to low elevation males (p = 0.016). When considering all sampled males, difference in T across elevation was not detected (p = 0.58), but when taking age into account, second years (SYs) at low elevation had lower T compared to SYs at high elevation (p = 0.016). Finally, PRL did not vary by elevation (p = 0.11), but we found a relationship between PRL and breeding status (p < 0.001) and a correlation between PRL and bird condition (p = 0.0052). Our results suggest that T and peak CORT may have a correlational relationship with avian malaria, and that these correlations are dependent on age and sex class, respectively.
