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

岛上鸟类和其他动物面临的最大威胁之一是外来的入侵寄生虫。其中一个最好的例子是寄生在Galápagos群岛达尔文雀身上的巢蝇。这种原产于南美洲大陆的苍蝇以雏鸟的血为食，雏鸟经常因此而死亡。唐氏弓形虫是导致几种雀类数量迅速减少的主要原因，其中包括濒临灭绝的红树林雀，目前只剩下不到100只。这种苍蝇造成的威胁可能会因其他种类的鸟类对这种苍蝇的容忍度而加剧。容忍的宿主，如Galápagos反舌鸟，体型比雀类大，繁殖季节更早，在苍蝇的失血中幸存下来，仍然成功地离开了巢。因此，如果寄主是寄生在雀身上的苍蝇的来源，那么它们就有可能放大苍蝇对雀的威胁。本研究的目的是检验这种放大假设。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），它将允许生物学家、Galápagos国家公园护林员和其他人每年跟踪苍蝇数量的数据。记录反舌鸟对雀鸟的间接影响，以及对飞禽数量的长期监测，将为保护工作做出根本性的贡献。寄生蝇的传播将使用基于来自果蝇全基因组序列的snp的精细尺度种群遗传和亲缘关系方法来测量（目的1）。接下来，实验将测试被寄生的反舌鸟巢穴是否会增加附近雀巢中的downsi的数量（Aim 2），以及苍蝇是否会降低雀的繁殖成功率（Aim 3）。模仿鸟的巢将被GPS定位，并随机分配到实验或控制处理。拟嘲鸟的巢将用氯菊酯熏蒸，以杀死巢中的苍蝇。每个反舌鸟巢35米内的雀巢也将被GPS定位，并量化苍蝇的数量和雀的繁殖成功率。实验数据将用于扩展和参数化已发表的中等地雀种群生存能力模型（目标4）。这个新模型将测试在多大程度上接近耐抗性的反舌鸟，以及其他环境因素，放大了唐氏弓形虫对达尔文雀的威胁。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.