The introduction of non-native species and reductions in native biodiversity have resulted in substantial changes in vector and host communities globally, but the consequences for pathogen transmission are poorly understood. In lowland Hawai'i, bird communities are composed of primarily introduced species, with scattered populations of abundant native species. We examined the influence of avian host community composition-specifically the role of native and introduced species, as well as host diversity, on the prevalence of avian malaria (Plasmodium relictum) in the southern house mosquito (Culex quinquefasciatus). We also explored the reciprocal effect of malaria transmission on native host populations. Avian malaria infection prevalence in mosquitoes increased with the density and relative abundance of native birds, as well as host community competence, but was uncorrelated with host diversity. Avian malaria transmission was estimated to reduce population growth rates of Hawai'i 'amakihi (Chlorodrepanis virens) by 7-14%, but mortality from malaria could not explain gaps in this species' distribution at our sites. Our results suggest that in Hawai'i native host species increase pathogen transmission to mosquitoes, but introduced species can also support malaria transmission alone. The increase in pathogen transmission with native bird abundance leads to additional disease mortality in native birds, further increasing disease impacts in an ecological feedback cycle. In addition, vector abundance was higher at sites without native birds and as a result overwhelmed the effects of host community composition on transmission such that infected mosquito abundance was highest at sites without native birds. Higher disease risk at these sites due to higher vector abundance could inhibit recolonization and recovery of native species to these areas. More broadly, this work shows how differences in host competence for a pathogen among native and introduced taxa can influence transmission and highlights the need to examine this question in other systems to determine the generality of this result.

中文翻译：

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夏威夷本土和引进鸟类在禽疟疾传播中的作用

非本地物种的引入和本地生物多样性的减少导致全球媒介和寄主社区发生重大变化，但对病原体传播的后果知之甚少。在夏威夷低地，鸟类群落主要由引进物种组成，散布着丰富的本地物种。我们研究了鸟类宿主群落组成的影响——特别是本地和引进物种的作用，以及宿主多样性，对南方家蚊（Culex quinquefasciatus）中禽疟疾（Plasmodium relictum）流行的影响。我们还探讨了疟疾传播对本地宿主种群的相互影响。蚊子中的禽疟疾感染流行率随着本土鸟类的密度和相对丰度而增加，以及宿主社区能力，但与宿主多样性无关。据估计，禽疟疾传播使 Hawai'i 'amakihi (Chlorodrepanis virens) 的人口增长率降低了 7-14%，但疟疾导致的死亡率无法解释该物种在我们所在地的分布差异。我们的结果表明，夏威夷本地宿主物种会增加病原体向蚊子的传播，但引入的物种也可以单独支持疟疾传播。病原体传播随着本地鸟类数量的增加而增加，导致本地鸟类的疾病死亡率增加，进一步增加了生态反馈循环中的疾病影响。此外，在没有本土鸟类的地点，媒介丰度更高，因此超过了宿主群落组成对传播的影响，因此在没有本土鸟类的地点，受感染的蚊子丰度最高。由于较高的病媒丰度，这些地点的疾病风险较高，可能会抑制本地物种在这些地区的重新定殖和恢复。更广泛地说，这项工作显示了本地和引入的分类群中病原体宿主能力的差异如何影响传播，并强调需要在其他系统中检查这个问题以确定该结果的普遍性。