Tripet F, Richner H
Zoology Department, University of Bern, Hinterkappelen, Switzerland.
Parasitology. 1997 Oct;115 ( Pt 4):419-27. doi: 10.1017/s0031182097001467.
Hosts exert selection pressures on their parasites and it is often assumed that host-parasite coevolution with each host is less intense in a generalist parasite than for a parasite with a narrow host range. Selection pressure on the parasite, however, is rather determined by host specificity, i.e. the relative importance of each host, than simply by the range of hosts. The determination of host specificity requires an assessment of the prevalence and intensity of parasite infestation within each host's nests, as well as the local abundance of each host species. Since the hen flea, Ceratophyllus gallinae, is a rather generalist parasite of birds it could be concluded that there has been weak coevolution with each of its hosts. By reviewing the literature on the prevalence and intensity of hen flea infestations in bird nests we estimated the number of individuals produced in the nest of each host species. The comparative analysis shows (1) that the prevalence of infestation is highest in hole-nesting avian families, (2) that prevalence and intensity of infestation among bird families are highly correlated, and (3) that hole-nesting Paridae have the highest intensities of infestation and harbour the majority of the flea population. These results underline the fleas' potential for coevolution with Paridae despite their extensive host range.
宿主会对其寄生虫施加选择压力，通常认为，与宿主范围狭窄的寄生虫相比，泛寄生物与每个宿主之间的共同进化强度较低。然而，寄生虫所面临的选择压力更多地取决于宿主特异性，即每个宿主的相对重要性，而不仅仅取决于宿主范围。确定宿主特异性需要评估每个宿主巢穴内寄生虫感染的流行程度和强度，以及每个宿主物种在当地的丰度。由于鸡蚤（Ceratophyllus gallinae）是一种相当泛化的鸟类寄生虫，因此可以得出结论，它与每个宿主的共同进化都很弱。通过回顾关于鸟巢中鸡蚤感染流行程度和强度的文献，我们估计了每个宿主物种巢穴中产生的个体数量。比较分析表明：（1）在洞巢鸟类家族中感染率最高；（2）鸟类家族之间的感染流行程度和强度高度相关；（3）洞巢山雀科的感染强度最高，且容纳了大部分跳蚤种群。这些结果强调了尽管跳蚤宿主范围广泛，但仍有与山雀科共同进化的潜力。
