Osnas E E, Lively C M
Department of Biology, Indiana University, Bloomington, IN 47401-3700, USA.
Parasitology. 2004 Feb;128(Pt 2):223-8. doi: 10.1017/s0031182003004360.
Parasites have been found to be more infective to sympatric hosts (local adaptation) in some systems but not in others. The variable nature of results might arise due to differences in host and/or parasite migration rates, parasite virulence, specificity of infection, and to differences in the dose-response functions. We tested this latter possibility by manipulating the dose of trematode (Microphallus sp.) eggs on sympatric and allopatric host populations (Potamopyrgus antipodarum). We found that infection rapidly increased to a high asymptote (0.88 +/- 0.02, 1 S.E.) in the sympatric host population, but infections were low and surprisingly unrelated to dose in the allopatric host. We also found that host survival and growth rate were not negatively affected by increasing parasite dose in either population. These results suggest that defences in the allopatric host were not overwhelmed at high parasite doses, and that any life-history costs of defence are not plastic responses to parasite dose.
在某些系统中，已发现寄生虫对同域宿主（本地适应性）的感染性更强，但在其他系统中并非如此。结果的可变性质可能是由于宿主和/或寄生虫迁移率、寄生虫毒力、感染特异性以及剂量反应函数的差异所致。我们通过操纵同域和异域宿主种群（新西兰泥蜗）上吸虫（微茎属）卵的剂量来测试后一种可能性。我们发现，在同域宿主种群中，感染率迅速上升至一个高渐近线（0.88±0.02，1个标准误差），但在异域宿主中感染率较低，且令人惊讶的是与剂量无关。我们还发现，在这两个种群中，增加寄生虫剂量均未对宿主的生存和生长率产生负面影响。这些结果表明，在高寄生虫剂量下，异域宿主的防御并未被压倒，并且防御的任何生活史成本都不是对寄生虫剂量的可塑性反应。
