Leibniz Institute of Marine Sciences (IFM-GEOMAR), Evolutionary Ecology of Marine Fishes, Kiel, Germany.
PLoS One. 2012;7(1):e30658. doi: 10.1371/journal.pone.0030658. Epub 2012 Jan 27.
Extreme climate events such as heat waves are expected to increase in frequency under global change. As one indirect effect, they can alter magnitude and direction of species interactions, for example those between hosts and parasites. We simulated a summer heat wave to investigate how a changing environment affects the interaction between the broad-nosed pipefish (Syngnathus typhle) as a host and its digenean trematode parasite (Cryptocotyle lingua). In a fully reciprocal laboratory infection experiment, pipefish from three different coastal locations were exposed to sympatric and allopatric trematode cercariae. In order to examine whether an extreme climatic event disrupts patterns of locally adapted host-parasite combinations we measured the parasite's transmission success as well as the host's adaptive and innate immune defence under control and heat wave conditions. Independent of temperature, sympatric cercariae were always more successful than allopatric ones, indicating that parasites are locally adapted to their hosts. Hosts suffered from heat stress as suggested by fewer cells of the adaptive immune system (lymphocytes) compared to the same groups that were kept at 18°C. However, the proportion of the innate immune cells (monocytes) was higher in the 18°C water. Contrary to our expectations, no interaction between host immune defence, parasite infectivity and temperature stress were found, nor did the pattern of local adaptation change due to increased water temperature. Thus, in this host-parasite interaction, the sympatric parasite keeps ahead of the coevolutionary dynamics across sites, even under increasing temperatures as expected under marine global warming.
极端气候事件，如热浪，预计在全球变化下会增加频率。作为间接影响之一，它们可以改变物种相互作用的幅度和方向，例如宿主和寄生虫之间的相互作用。我们模拟了夏季热浪，以研究环境变化如何影响宽吻海龙（Syngnathus typhle）作为宿主与其双腔吸虫（Cryptocotyle lingua）寄生虫之间的相互作用。在一个完全互惠的实验室感染实验中，来自三个不同沿海地区的海龙暴露于同域和异域的吸虫尾蚴。为了研究极端气候事件是否会破坏本地适应的宿主-寄生虫组合模式，我们测量了寄生虫的传播成功率以及宿主在对照和热浪条件下的适应性和先天免疫防御。与温度无关，同域尾蚴总是比异域尾蚴更成功，这表明寄生虫是在本地适应其宿主的。与在 18°C 下保持的相同组相比，宿主的适应性免疫系统（淋巴细胞）细胞较少，表明它们受到了热应激的影响。然而，在 18°C 的水中，先天免疫细胞（单核细胞）的比例更高。与我们的预期相反，我们没有发现宿主免疫防御、寄生虫感染力和温度应激之间存在相互作用，也没有发现由于水温升高而改变本地适应的模式。因此，在这种宿主-寄生虫相互作用中，即使在海洋全球变暖下预计会增加的温度下，同域寄生虫也能领先于跨地点的协同进化动态。
