Tepolt Carolyn K, Darling John A, Blakeslee April M H, Fowler Amy E, Torchin Mark E, Miller A Whitman, Ruiz Gregory M
Department of Biology Woods Hole Oceanographic Institution Woods Hole MA USA.
Smithsonian Environmental Research Center Edgewater MD USA.
Evol Appl. 2019 Sep 25;13(3):545-558. doi: 10.1111/eva.12865. eCollection 2020 Mar.
Parasitism can represent a potent agent of selection, and introduced parasites have the potential to substantially alter their new hosts' ecology and evolution. While significant impacts have been reported for parasites that switch to new host species, the effects of macroparasite introduction into naïve populations of host species with which they have evolved remain poorly understood. Here, we investigate how the estuarine white-fingered mud crab () has adapted to parasitism by an introduced rhizocephalan parasite () that castrates its host. While the host crab is native to much of the East and Gulf Coasts of North America, its parasite is native only to the southern end of this range. Fifty years ago, the parasite invaded the mid-Atlantic, gradually expanding through previously naïve host populations. Thus, different populations of the same host species have experienced different degrees of historical interaction (and thus potential evolutionary response time) with the parasite: long term, short term, and naïve. In nine estuaries across this range, we examined whether and how parasite prevalence and host susceptibility to parasitism differs depending on the length of the host's history with the parasite. In field surveys, we found that the parasite was significantly more prevalent in its introduced range (i.e., short-term interaction) than in its native range (long-term interaction), a result that was also supported by a meta-analysis of prevalence data covering the 50 years since its introduction. In controlled laboratory experiments, host susceptibility to parasitism was significantly higher in naïve hosts than in hosts from the parasite's native range, suggesting that host resistance to parasitism is under selection. These results suggest that differences in host-parasite historical interaction can alter the consequences of parasite introductions in host populations. As anthropogenically driven range shifts continue, disruptions of host-parasite evolutionary relationships may become an increasingly important driver of ecological and evolutionary change.
寄生现象可能是一种强大的选择因素，外来寄生虫有可能极大地改变其新宿主的生态和进化。虽然已报道了寄生虫转移到新宿主物种后产生的重大影响，但对于大型寄生虫引入与其共同进化的宿主物种的未接触群体所产生的影响，人们仍知之甚少。在此，我们研究河口白指招潮蟹（）如何适应一种外来的根头目寄生虫（）的寄生，这种寄生虫会阉割其宿主。虽然宿主蟹原产于北美东海岸和墨西哥湾的大部分地区，但其寄生虫仅原产于该分布范围的南端。50年前，这种寄生虫侵入了大西洋中部，逐渐在以前未接触过的宿主群体中扩散。因此，同一宿主物种的不同群体与寄生虫经历了不同程度的历史相互作用（以及潜在的进化反应时间）：长期、短期和未接触。在这个分布范围内的九个河口，我们研究了寄生虫的感染率以及宿主对寄生的易感性是否以及如何因宿主与寄生虫的历史接触时长而有所不同。在实地调查中，我们发现该寄生虫在其引入地区（即短期相互作用）的感染率显著高于其原生地区（长期相互作用），这一结果也得到了对其引入后50年感染率数据的荟萃分析的支持。在受控实验室实验中，未接触过寄生虫的宿主对寄生的易感性显著高于来自寄生虫原生地区的宿主，这表明宿主对寄生的抵抗力正在受到选择。这些结果表明，宿主 - 寄生虫历史相互作用的差异会改变寄生虫引入对宿主群体的影响。随着人为驱动的分布范围变化持续存在，宿主 - 寄生虫进化关系的破坏可能会成为生态和进化变化的一个越来越重要的驱动因素。
