Do tolerant hosts amplify the threat of invasive parasites? Darwin’s finches, mockingbirds, and nest flies.

对岛屿鸟类和其他动物的最大威胁之一是非本地的入侵寄生虫。其中一个最好的例子是寄生在加拉帕戈斯群岛的达尔文雀的巢蝇。 这种苍蝇原产于南美洲大陆，以雏鸟的血液为食，结果往往导致雏鸟死亡。 唐氏雀是几种雀迅速减少的主要原因，包括红树林雀，它濒临灭绝，只剩下不到100只。 苍蝇造成的威胁可能会因其他鸟类而加剧，这些鸟类是苍蝇的耐受宿主。 容忍宿主，如加拉帕戈斯嘲鸫，体型比雀类大，在季节中繁殖较早，在苍蝇失血后幸存下来，仍然成功地离开巢穴。 因此，宽容的主机有可能放大苍蝇的威胁，以雀，如果他们是一个来源的苍蝇寄生雀。本研究的目的是检验这种放大假说。作为这项工作更广泛影响的一部分，研究人员将创建一个智能手机应用程序（FlyTracker），允许生物学家，加拉帕戈斯国家公园护林员和其他人每年跟踪苍蝇数量的数据。 记录嘲鸟对雀类的间接影响，以及对蝇类丰度的长期监测，将从根本上促进保护工作。寄生蝇类的扩散将使用基于蝇类全基因组序列的SNPs的精细规模种群遗传和亲缘关系方法进行测量（目标1）。接下来，一项实验将测试寄生的嘲鸟巢是否会增加附近雀巢中的P. downsi数量（目标2），以及苍蝇是否会降低雀的繁殖成功率（目标3）。 知更鸟的巢将通过GPS定位，并随机分配到实验或对照处理组。实验性的嘲鸟巢将用氯菊酯熏蒸，氯菊酯可以杀死鸟巢里的苍蝇。每个嘲鸟巢35米范围内的雀巢也将被GPS定位，苍蝇的数量和雀的繁殖成功率将被量化。从实验中获得的数据将被用来扩展和参数化一个已发表的人口生存力模型中地面雀（目标4）。新的模型将测试在何种程度上接近宽容的嘲鸟，以及其他环境因素，放大的威胁P. downsi的达尔文的finches.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

One of the greatest threats to island birds and other animals is invasive parasites that are not native. One of the best examples is the nest fly Philornis downsi, which parasitizes Darwin’s finches in the Galápagos Islands. The fly, which is native to mainland South America, feeds on blood of nestling finches, which often die as a result. P. downsi is a major cause of rapid declines in several species of finches, including the Mangrove Finch, which is in imminent risk of extinction, with fewer than 100 individuals remaining. The threat posed by the flies may be exacerbated by other species of birds that are tolerant hosts of the fly. Tolerant hosts, such as Galápagos mockingbirds, which are larger in size than finches and breed earlier in the season, survive blood loss to flies and still leave the nest successfully. Thus, tolerant hosts have the potential to amplify the threat of flies to finches if they are a source of the flies that parasitize finches. The goal of this study is to test this amplification hypothesis. As part of the broader impacts of this work, the researchers will create a smartphone app (FlyTracker) that will allow biologists, Galápagos National Park rangers, and others to track data on the abundance of flies from year to year. Documentation of the indirect effects of mockingbirds on finches, together with long term monitoring of fly abundance, will contribute in a fundamental way to conservation efforts.Dispersal of parasitic flies will be measured using a fine-scale population genetic and kinship approach based on SNPs from whole genome sequences of flies (Aim 1). Next, an experiment will test whether parasitized mockingbird nests increase the number of P. downsi in nearby finch nests (Aim 2), and whether flies decrease the reproductive success of finches (Aim 3). Mockingbird nests will be GPS located and randomly assigned to experimental or control treatments. Experimental mockingbird nests will be fumigated with permethrin, which kills flies in nests. Finch nests within 35m of each mockingbird nest will also be GPS located, and the number of flies and reproductive success of finches will be quantified. Data from the experiment will be used to expand and parameterize a published population viability model for medium ground finches (Aim 4). The new model will test the degree to which proximity to tolerant mockingbirds, as well as other environmental factors, amplifies the threat of P. downsi to Darwin's finches.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.