Effects of the introduced parasite Philornis downsi on nestling growth and mortality in the medium ground finch (Geospiza fortis)
Effects of the introduced parasite Philornis downsi on nestling growth and mortality in the medium ground finch (Geospiza fortis)
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DOI：
10.1016/j.biocon.2007.11.012
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发表时间：
2008-02-01
影响因子：
5.9
通讯作者：
Huber, Sarah K.
中科院分区：
文献类型：
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作者：
Huber, Sarah K.
入侵物种有可能通过竞争或直接捕食本地生物而对本地生态系统产生不利影响，并与当地种群的灭绝有关。加拉帕戈斯群岛的一种具有潜在破坏性的外来物种是寄生蝇 Philornis downsi。作为幼虫，P. downsi 寄生于雏鸟，并与雏鸟死亡率高和生长速度降低有关。在这里，我记录了中地雀 (Geospiza fortis) 双峰种群中雏鸟的生长和死亡率。观测工作历时三年，在不同的生态条件下进行。巢中寄生虫的年流行率为 64% 至 98%，有寄生虫的巢中的雏鸟死亡率为 16% 至 37%。寄生虫负荷和每个雏鸟的寄生虫负荷遵循偏态分布，许多巢穴的寄生虫相对较少，而少数巢穴的寄生虫较多。然而，寄生虫负载与繁殖开始、窝数、雏鸟数量、雏鸟存活率或雏鸟成功率无关。另一方面，每只雏鸟的寄生虫数量与产卵开始日期和在被寄生的巢中死亡的雏鸟的比例相关。被寄生和未被寄生的巢中雏鸟的大小和生长速度都没有差异。此外，雄性和雌性喙的形态与寄生虫数量、繁殖变量或雏鸟存活率无关。因此，虽然寄生造成的总体死亡率很高，但生态条件和可能的宿主防御可能会抵消 P. downsi 对雏鸟大小和生长的一些有害影响。这些结果综合表明，P. downsi 幼虫寄生在雏鸟 G. fortis 上有可能导致种群数量大幅下降。 (C) 2007 Elsevier Ltd. 保留所有权利。
Invasive species have the potential to detrimentally affect native ecosystems by out competing or directly preying upon native organisms, and have been implicated in the extinction of endemic populations. one potentially devastating introduced species in the Galapagos Islands is the parasitic fly Philornis downsi. As larvae, P. downsi parasitize nestling birds and have been associated with high nestling mortality and reduced growth rates. Here I document nestling growth and mortality in a bimodal population of the medium ground finch, Geospiza fortis. observations were conducted over three years, and under variable ecological conditions. Annual parasite prevalence in nests ranged from 64% to 98%, and nestling mortality in nests with parasites ranged from 16% to 37%. Parasite load and parasite load per nestling follow a skewed distribution with many nests having relatively few parasites, and few nest having many. Parasite load, however, was not correlated with onset of breeding, clutch size, the number of nestlings, nestling survival or fledgling success. Parasite load per nestling, on the other hand, was correlated with clutch initiation date and the proportion of nestlings that died in parasitized nests Neither nestling size nor growth rate differed between parasitized and unparasitized nests. In addition, male and female beak morphology was not correlated with parasite load, breeding variables or nestling survival. Thus, while overall mortality due to parasitism is high, ecological conditions and possible host defenses may potentially counter some of the detrimental affects of P. downsi on nestling size and growth. These results taken together suggest that parasitism of P. downsi larvae on nestling G. fortis has the potential to lead to large population declines. (C) 2007 Elsevier Ltd. All rights reserved.