Many hypotheses attempt to explain parasite–host associations, but rarely are they examined together in a single community. For hosts, key traits are the proportion of infected individuals (prevalence) and the diversity of parasites infecting them. A key parasite trait is host specificity, ranging from specialists infecting one or a few closely related species to generalists infecting many species. We tested 10 hypotheses to explain host‐parasite associations; five ‘host‐centric’ (e.g. prevalence is related to host abundance) and five ‘parasite‐centric’ (e.g. parasite abundance is related to host specificity). We analyzed a community of 67 locally transmitted avian haemosporidian parasite lineages (genera Plasmodium, Haemoproteus or Leucocytozoon), sampled from 2726 birds (64 species) in southern Sweden. Among host‐centric hypotheses, Haemoproteus and Leucocytozoon prevalence and Haemoproteus diversity were related to host habitat preferences, whereas there were no relationships with host abundance or body mass. Haemoproteus and Leucocytozoon prevalences were more similar among closely related than among distantly related host species. Haemoproteus prevalence and diversity were lower in host species with few close relatives (‘evolutionarily distinct’ hosts). Among parasite‐centric hypotheses, most lineages, even relative generalists, infected closely related host species more often than expected by chance. However, the host species of Haemoproteus and Leucocytozoon lineages overlapped less among lineages than expected by chance. Specialists did not reach higher prevalences than generalists on single host species. However, the abundance of Haemoproteus lineages was related to host specificity with generalists more common than specialists; this was driven by three closely related generalists. Host specificity of parasites was unrelated to the abundance or evolutionarily distinctiveness of their hosts. Parasite communities are likely structured by many factors and cannot be explained by hypotheses focusing solely on hosts or parasites. However, we found consistent effects of host phylogenetic relationships, plausibly a result of evolutionarily conserved host immune systems limiting parasite distributions.

中文翻译：

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解释禽血孢子虫寄生虫社区中的流行，多样性和宿主特异性

许多假设试图解释寄生虫与宿主之间的关联，但很少在一个共同的社区中对其进行检验。对于寄主而言，关键特征是感染个体的比例（患病率）和感染他们的寄生虫的多样性。关键的寄生虫性状是宿主特异性，范围从感染一个或几个密切相关物种的专家到感染许多物种的通才。我们测试了10个假设以解释宿主-寄生虫的关联。五种“以寄主为中心”（例如，患病率与寄主的丰度相关）和五种“寄生虫为中心”（例如，寄生虫的丰度与寄主的特异性相关）。我们分析了67个本地传播的禽血孢子虫寄生虫谱系（疟原虫，血红蛋白或白细胞虫属）的群落。），取材于瑞典南部的2726羽鸟类（64种）。在以寄主为中心的假说中，变形杆菌和白血球菌的患病率以及变形杆菌的多样性与寄主生境的偏好有关，而与寄主的丰度或体重无关。亲缘关系较远缘宿主物种之间的变形杆菌和白细胞共生流行更为相似。变形蛋白在近亲很少的寄主物种（“进化上不同的”寄主）中，流行和多样性较低。在以寄生虫为中心的假说中，大多数血统，甚至是相对通才，也比偶然地更多地感染了密切相关的寄主物种。但是，血红蛋白和白细胞增生谱系的宿主物种在谱系中的重叠少于偶然的预期。在单个寄主物种上，专家的流行率没有比通才高。但是，血红蛋白丰富谱系与宿主的特异性有关，通才比专家更普遍；这是由三位密切相关的通才推动的。寄生虫的寄主特异性与寄主的丰度或进化上的独特性无关。寄生虫群落可能由许多因素构成，不能仅通过针对寄主或寄生虫的假设来解释。但是，我们发现了宿主系统发生关系的一致影响，这很可能是进化保守的宿主免疫系统限制了寄生虫分布的结果。