College of Science and Engineering, Flinders University, Bedford Park, SA, 5001, Australia.
Department of Behavioral and Cognitive Biology, Konrad Lorenz Research Center, Core Facility for Behavior and Cognition, University of Vienna, Vienna, Austria.
Sci Rep. 2021 Aug 4;11(1):15832. doi: 10.1038/s41598-021-94996-7.
In invasive parasites, generalism is considered advantageous during the initial phase of introduction. Thereafter, fitness costs to parasites, such as host-specific mortality, can drive parasites towards specialism to avoid costly hosts. It is important to determine changes in host specificity of invasive populations to understand host-parasite dynamics and their effects on vulnerable host populations. We examined changes in mortality in the introduced avian vampire fly (Philornis downsi) (Diptera: Muscidae), a generalist myasis-causing ectoparasite, between 2004 and 2020 on Floreana Island (Galápagos). Mortality was measured as the proportion of immature larvae found upon host nest termination. Over the time period, the avian vampire fly was most abundant and had low mortality in nests of the critically endangered medium tree finch (Camarhynchus pauper) and had the highest mortality in nests of hybrid tree finches (Camarhynchus spp.). Low larval mortality was also found in small tree (Camarhynchus parvulus) and small ground finch (Geospiza fuliginosa) nests. Selection could favour avian vampire flies that select medium tree finch nests and/or avoid hybrid nests. Overall, the finding of differences in avian vampire fly survival across host species is parsimonious with the idea that the introduced fly may be evolving towards host specialisation.
在入侵寄生虫中，一般性被认为在引入的初始阶段是有利的。此后，寄生虫的适应成本，如宿主特异性死亡率，可以驱使寄生虫向专门化发展，以避免代价高昂的宿主。确定入侵种群的宿主特异性变化对于了解宿主-寄生虫动态及其对脆弱宿主种群的影响非常重要。我们研究了 2004 年至 2020 年期间，加拉帕戈斯群岛弗洛雷纳岛上普遍存在的寄生虫——吸血蝇（Philornis downsi）（双翅目：蝇科）死亡率的变化，这种寄生虫是一种引起蝇蛆病的一般性外寄生虫。死亡率的衡量标准是在宿主巢终止时发现的未成熟幼虫的比例。在这段时间内，吸血蝇在极度濒危的中型树雀（Camarhynchus pauper）的巢中最丰富，死亡率最低，在杂种树雀（Camarhynchus spp.）的巢中死亡率最高。在小树雀（Camarhynchus parvulus）和小地雀（Geospiza fuliginosa）的巢中也发现了较低的幼虫死亡率。选择可能有利于选择中型树雀巢并/或避免杂交巢的吸血蝇。总的来说，宿主物种间吸血蝇存活率差异的发现与这样一种观点是一致的，即引入的蝇可能正在向宿主专门化进化。
