MATSON, K.D.*; KLASING, K.C.; SCHEUERLEIN, A.; RICKLEFS, R.E.; University of Missouri-St. Louis; University of California-Davis; University of Missouri-St. Louis; University of Missouri-St. Louis: Immune function differences between continental and island forms: a symptom of an �island syndrome�?

Assuming immune defenses are costly, birds with an evolutionary history on relatively disease-free, oceanic islands should exhibit reduced immune function as part of a general �island syndrome� of reduced interspecific (in this case, parasite-host) interactions. In fact, some endemic birds of Hawaii have experienced population declines because of their failure to resist infection by introduced pathogens. We measured several components of the immune system in birds from continents and oceanic islands to investigate the evolutionary lability of immune function. Comparisons were made between 15 phylogenetically matched pairs of species/populations in North America and on the islands of Hawaii, Bermuda and the Galapagos. The island populations included endemics, natives, and recent introductions. We employed three protocols to measure eight variables: hemolysis, hemagglutination, haptoglobin concentration, and enumeration of five leukocytes types. All assays were based on a single blood sample subdivided into cellular (blood smear) and plasma (frozen until analysis) components. Implications of this study for conservation of island species, and more generally for evolutionary and physiological ecology, will be discussed.