Feis Marieke E, Goedknegt M Anouk, Thieltges David W, Buschbaum Christian, Wegner K Mathias
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Wadden Sea Station Sylt, Hafenstraße 43, D-25992 List/Sylt, Germany.
NIOZ Royal Netherlands Institute for Sea Research, Department of Coastal Systems, and Utrecht University, P.O. Box 59, 1790 AB, Den Burg, Texel, Netherlands.
Zoology (Jena). 2016 Aug;119(4):366-74. doi: 10.1016/j.zool.2016.05.012. Epub 2016 May 27.
Host-parasite coevolution has rarely been observed in natural systems. Its study often relies on microparasitic infections introducing a potential bias in the estimation of the evolutionary change of host and parasite traits. Using biological invasions as a tool to study host-parasite coevolution in nature can overcome these biases. We demonstrate this with a cross-infection experiment in the invasive macroparasite Mytilicola intestinalis and its bivalve host, the blue mussel Mytilus edulis. The invasion history of the parasite is well known for the southeastern North Sea and is characterised by two separate invasion fronts that reached opposite ends of the Wadden Sea (i.e. Texel, The Netherlands and Sylt, Germany) in a similar time frame. The species' natural history thus makes this invasion an ideal natural experiment to study host-parasite coevolution in nature. We infected hosts from Texel, Sylt and Kiel (Baltic Sea, where the parasite is absent) with parasites from Texel and Sylt, to form sympatric, allopatric and naïve infestation combinations, respectively. We measured infection rate, host condition and parasite growth to show that sympatric host-parasite combinations diverged in terms of pre- and post-infection traits within <100 generations since their introduction. Texel parasites were more infective and more efficient at exploiting the host's resources. Hosts on Texel, on the other hand, evolved resistance to infection, whereas hosts on Sylt may have evolved tolerance. This illustrates that different coevolutionary trajectories can evolve along separate invasion fronts of the parasite, highlighting the use of biological invasions in studies of host-parasite coevolution in nature.
宿主-寄生虫的协同进化在自然系统中很少被观察到。其研究通常依赖于微寄生虫感染，这在估计宿主和寄生虫性状的进化变化时会引入潜在偏差。利用生物入侵作为研究自然中宿主-寄生虫协同进化的工具可以克服这些偏差。我们通过对入侵性大型寄生虫肠内肌蛤及其双壳类宿主蓝贻贝进行交叉感染实验来证明这一点。该寄生虫在北海东南部的入侵历史为人熟知，其特点是有两个独立的入侵前沿，在相似的时间框架内到达了瓦登海的两端（即荷兰的泰瑟尔岛和德国的叙尔特岛）。因此，该物种的自然历史使这次入侵成为研究自然中宿主-寄生虫协同进化的理想自然实验。我们用来自泰瑟尔岛和叙尔特岛的寄生虫分别感染来自泰瑟尔岛、叙尔特岛和基尔（波罗的海，该寄生虫不存在）的宿主，以分别形成同域、异域和原始感染组合。我们测量了感染率、宿主状况和寄生虫生长情况，结果表明，自引入以来，同域宿主-寄生虫组合在不到100代的时间内，在感染前后的性状方面出现了分化。泰瑟尔岛的寄生虫感染性更强，在利用宿主资源方面更高效。另一方面，泰瑟尔岛的宿主进化出了对感染的抗性，而叙尔特岛的宿主可能进化出了耐受性。这表明不同的协同进化轨迹可以沿着寄生虫的不同入侵前沿进化，突出了生物入侵在自然中宿主-寄生虫协同进化研究中的应用。
