Raeymaekers Joost A M, Wegner K Mathias, Huyset Tine, Volckaert Filip A M
Laboratory of Animal Diversity and Systematics, Katholieke Universiteit Leuven, Ch. Deberiotstraat, 32, B-3000 Leuven, Belgium.
Folia Parasitol (Praha). 2011 Mar;58(1):27-34. doi: 10.14411/fp.2011.003.
Parasites with high host specificity maximally depend on their hosts, which should increase the likelihood of coevolution. However, coevolution requires reciprocal selection exerted by the host and the parasite, and thus a considerable level of parasite virulence. In species of the monogenean ectoparasite genus Gyrodactylus consecutive generations are confronted with a single host, which may constrain the evolution of virulence. Transmission, which is often important in the ecology of Gyrodactylus species, may have the opposite effect, but may also lead to the avoidance of coevolutionary arms races. We investigated the potential outcome of coevolution between Gyrodactylus gasterostei Gläser, 1974 and its host, the three-spined stickleback (Gasterosteus aculeatus L.) by determining the strength of genotype by genotype (GxG) interactions on two levels: within and between sympatric and allopatric host populations. To do so, we compared the parasite's infection dynamics on laboratory-reared sympatric (Belgian) and allopatric (German) hosts. We found that a parasite line successfully infected a range of sympatric host genotypes (represented by families), while it failed to establish on allopatric hosts. Phylogeographic studies suggest that neutral genetic divergence between the host populations cannot explain this dramatic difference. Provided that this result can be generalised towards other parasite lines, we conclude that coevolution in this host-parasite system is more likely to lead to local adaptation on the population level than to GxG interactions within populations.
宿主特异性高的寄生虫极大地依赖于它们的宿主，这应该会增加共同进化的可能性。然而，共同进化需要宿主和寄生虫相互施加选择，因此需要相当程度的寄生虫毒力。在单殖吸虫外寄生虫属三代虫属的物种中，连续几代都面对单一宿主，这可能会限制毒力的进化。传播在三代虫属物种的生态学中通常很重要，可能会产生相反的效果，但也可能导致避免共同进化的军备竞赛。我们通过在两个层面确定基因型与基因型（GxG）相互作用的强度，研究了1974年的腹三代虫及其宿主三刺鱼（Gasterosteus aculeatus L.）之间共同进化的潜在结果：同域和异域宿主种群内部以及之间。为此，我们比较了该寄生虫在实验室饲养的同域（比利时）和异域（德国）宿主上的感染动态。我们发现一个寄生虫品系成功感染了一系列同域宿主基因型（以家系表示），而在异域宿主上未能定殖。系统地理学研究表明，宿主种群之间的中性遗传差异无法解释这种巨大差异。如果这一结果能够推广到其他寄生虫品系，我们得出结论，在这个宿主-寄生虫系统中，共同进化更有可能导致种群水平上的局部适应，而不是种群内的GxG相互作用。
