Data from: Song sparrows Melospiza melodia have a home-field advantage in defending against sympatric malarial parasites

Hosts and parasites interact on both evolutionary and ecological time-scales. The outcome of these interactions, specifically whether hosts are more resistant to their local parasites (sympatric) than to parasites from another location (allopatric), is likely to affect the spread of infectious disease and the fitness consequences of host dispersal. We conducted a cross-infection experiment to determine whether song sparrows (Melospiza melodia) have an advantage in dealing with sympatric parasites. We captured birds from two breeding sites 437 km apart, and inoculated them with avian malaria (Plasmodium spp.) cultured either from their capture site or from the other site. Infection risk was lower for birds exposed to sympatric than to allopatric Plasmodium lineages, suggesting that song sparrows may have a home-field advantage in defending against local parasite strains. This pattern was more pronounced at one capture site than at the other, consistent with mosaic models of host-parasite interactions. Home-field advantage may arise from evolutionary processes, whereby host populations become adapted to their local parasites, and/or from ecological interactions, whereby host individuals develop resistance to the local parasites through previous immune exposure. Our findings suggest that greater susceptibility to novel parasites may represent a fitness consequence of natal dispersal.宿主与寄生虫在进化和生态两个时间尺度上存在相互作用。这些相互作用的结果——具体而言，即宿主对同域寄生虫（sympatric）的抗性是否强于对异域寄生虫（allopatric）的抗性——可能会影响传染病的传播，以及宿主扩散的适合度后果。我们开展了一项交叉感染实验，以探究歌带鹀（Melospiza melodia）在应对同域寄生虫时是否具备优势。我们从相距437公里的两个繁殖地捕捉了该鸟类，并将分别取自其捕捉地或另一繁殖地的禽疟原虫（Plasmodium spp.）培养液接种至受试个体体内。相较于暴露于异域疟原虫谱系的个体，接触同域疟原虫谱系的鸟类的感染风险更低，这表明歌带鹀在抵御本地寄生虫株系时或许拥有主场优势（home-field advantage）。这一现象在其中一个捕捉地表现得更为显著，与宿主-寄生虫相互作用镶嵌模型（mosaic models of host-parasite interactions）相符。主场优势可能源于两类过程：一是进化过程，即宿主种群适应其本地寄生虫；二是生态过程，即宿主个体通过先前的免疫暴露获得对本地寄生虫的抗性。我们的研究结果表明，对新型寄生虫的更高易感性或许是出生扩散（natal dispersal）带来的适合度代价。