Morphological measurements and mercury levels of Saltmarsh Sparrows sampled across their breeding range

Malaria parasites (genus Plasmodium) are important agents of infectious disease in birds and multiple factors including warming temperatures and environmental contamination may act to increase their geographic and host ranges. Here, we examined the role of geographical variation and environmental mercury exposure in malaria parasite infection dynamics in an imperiled songbird species with high mercury exposition, the Saltmarsh Sparrow (Ammospiza caudacutus). Using PCR methods, we screened 280 Saltmarsh Sparrows from across their breeding range for malaria parasite infection. We detected malaria parasites in 17% of sampled birds and a total of six Plasmodium lineages. Prevalence of infection and diversity of parasite lineages varied across the breeding range of the Saltmarsh Sparrow and increased at more northern latitudes. Although mercury is a known immunosuppressant and has been documented to alter an individual’s susceptibility to pathogens, we did not find a significant difference i..., ,

疟原虫（疟原虫属（Plasmodium））是鸟类重要的传染性病原，气温升高与环境污染等多种因素可能会扩大其地理分布范围与宿主范围。本研究以具有高汞暴露水平的受胁鸣禽物种盐沼带鹀（Ammospiza caudacutus）为研究对象，探讨了地理变异与环境汞暴露在疟原虫感染动态中的作用。我们采用聚合酶链式反应（PCR）技术，对其繁殖分布范围内的280只盐沼带鹀开展疟原虫感染筛查。结果显示，17%的采样个体携带疟原虫，共发现6个疟原虫谱系。感染率与寄生虫谱系多样性在盐沼带鹀的繁殖分布范围内存在差异，并随纬度升高而增加。尽管汞已被证实为免疫抑制剂，且可改变个体对病原体的易感性，但我们未发现显著差异……