Meeting Abstract

78.7  Friday, Jan. 6  Evidence of parasite-mediated selection favoring evolution of more effective immune defenses: more immune constituents in eggs of avian brood parasites HAHN, D. Caldwell*; IGL, Lawrence; BURNETT, James; ERF, Gisela; US Geological Survey - Patuxent WRC; US Geological Survey - No. Prairie WRC; University of Arkansas; University of Arkansas chahn@usgs.gov

Parasite-mediated selection should favor the evolution of more effective immune defenses in organisms whose life history entails exposure to a heightened diversity of parasites and foreign microbes. Good study species for examining how evolution shapes the design and function of the immune system in response to elevated exposure to parasites are the New World cowbirds (Icteridae, Molothrus spp), obligate brood parasites that include extreme host-generalist species. Two cowbird species lay their eggs in the nests of 200+ species and are thus exposed to the diverse parasites of their diverse foster parent species. We have previously shown several aspects of enhanced adult immunity in cowbird species and here report on greater maternal investment of immune factors in eggs of the brown-headed cowbird. We found that the eggs of this cowbird species have both higher lysozyme content and higher immunoglobulin content than do the eggs of a closely-related species, red-winged blackbird, that is not a brood parasite.