CEFE, CNRS, Univ Montpellier, Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier, France.
UMR 5290 MIVEGEC, Univ Montpellier, CNRS, IRD, Montpellier Cedex 5, France.
J Evol Biol. 2020 Dec;33(12):1704-1714. doi: 10.1111/jeb.13708. Epub 2020 Oct 11.
It is often difficult to determine why parasites do not evolve broader niches, especially when there are closely related and ecologically similar hosts available. We used an experimental evolution approach to test whether source-sink demography or trade-offs drive specialization, and its underlying traits, in two microsporidian parasites infecting two brine shrimp species. In the field, both parasites regularly infect both hosts, but experiments have shown that they are partially specialized. We serially passaged the parasites on one, the other, or an alternation of the two hosts; after 10 passages, we assayed the infectivity, virulence, and spore production of the evolved lines. Our results indicated a weak between-host trade-off acting on infectivity, but a strong trade-off acting on spore production. Consequently, spore production maintained both parasites' overall pattern of specialization. This study highlights that when trade-off shapes differ among traits, one key trait can prevent the evolution of generalism.
通常很难确定寄生虫为什么没有进化出更广泛的生态位，特别是当有密切相关且生态相似的宿主可供利用时。我们使用实验进化的方法来测试源-汇种群动态或权衡是否驱动了两种感染卤虫的微孢子虫寄生虫的专业化及其潜在特征。在野外，两种寄生虫都会定期感染两种宿主，但实验表明它们具有部分专业化特征。我们连续将寄生虫在一种、另一种或两种宿主之间交替传代；经过 10 次传代后，我们检测了进化系的感染力、毒力和孢子产量。我们的结果表明，在感染力上存在较弱的种间权衡，但在孢子产量上存在较强的权衡。因此，孢子产量维持了两种寄生虫的整体专业化模式。这项研究强调，当不同特征之间存在权衡时，一个关键特征可以防止一般性的进化。
