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

对岛鸟和其他动物最大的威胁之一是非本地的入侵寄生虫。最好的例子之一就是寄生在加拉帕戈斯群岛达尔文雀类上的雀巢苍蝇Philorris down si。这种苍蝇原产于南美洲大陆，以雏鸟的血液为食，而雏鸟经常因此而死亡。绒毛雀是几种雀类迅速减少的主要原因，包括红树林雀，这种雀濒临灭绝，只剩下不到100只。苍蝇构成的威胁可能会因其他种类的鸟类而加剧，这些鸟类是苍蝇的宽容宿主。耐受的宿主，如加拉帕戈斯嘲鸟，体型比雀类大，在季节较早的时候繁殖，在苍蝇失血后存活下来，仍然成功地离开了巢。因此，如果耐受性宿主是寄生雀类的苍蝇的来源，那么它们就有可能放大苍蝇对雀类的威胁。本研究的目的是检验这一放大假说。作为这项工作更广泛影响的一部分，研究人员将创建一款智能手机应用程序(FlyTracker)，使生物学家、加拉帕戈斯国家公园护林员和其他人能够跟踪每年苍蝇数量的数据。记录模拟鸟类对雀类的间接影响，以及对苍蝇丰度的长期监测，将从根本上有助于保护工作。将使用基于苍蝇全基因组序列SNP的精细种群遗传和亲属关系方法来测量寄生苍蝇的分布(目标1)。接下来，一项实验将测试被寄生的知更鸟巢是否会增加附近鸟巢中的绒毛虫数量(目标2)，以及苍蝇是否会降低雀类的繁殖成功率(目标3)。知更鸟的鸟巢将由GPS定位，并随机分配给实验或对照处理。试验性的知更鸟巢将被氯氰菊酯熏蒸，氯氰菊酯可以杀死巢中的苍蝇。每个知更鸟巢周围35米内的鸟巢也将被GPS定位，苍蝇的数量和雀类的繁殖成功将被量化。来自实验的数据将被用来扩展和参数化已发表的中型地雀种群生存模型(目标4)。新的模型将测试与耐受的嘲鸟的接近程度，以及其他环境因素，放大唐氏菌对达尔文鸟类的威胁。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势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.