近日，
研究人员表明，当海洋中的三刺鱼在淡水湖中定居时，它们获得了对淡水相关裂头绦虫的抗性。广泛的腹膜纤维化和炎症是一种普遍观察到的表型，有助于抑制绦虫的生长和生存能力，但也对繁殖力造成了巨大的损失。结合遗传图谱和种群基因组学，研究人员发现相反的选择在耐受性和抗性种群之间产生了免疫系统的差异，与发散优化相一致。
据了解，寄生虫对其宿主施加了适应性成本。生物学家通常认为，自然选择有利于抗感染的宿主。然而，当免疫反应本身有代价时，理论表明，选择有时可能有利于抵抗力的丧失，这可能导致替代的稳定状态，即一些种群有抵抗力，另一些种群有耐受力。免疫成本的种内变化很少以测试演化模式的方式进行调查，而且很少有适应性丧失抵抗力的例子。
附：英文原文
Title: Evolutionary gain and loss of a pathological immune response to parasitism
Author: Jesse N. Weber, Natalie C. Steinel, Foen Peng, Kum Chuan Shim, Brian K. Lohman, Lauren E. Fuess, Swapna Subramanian, Stephen P. De Lisle, Daniel I. Bolnick
Issue&Volume: 2022-09-09
Abstract: Parasites impose fitness costs on their hosts. Biologists often assume that natural selection favors infection-resistant hosts. Yet, when the immune response itself is costly, theory suggests that selection may sometimes favor loss of resistance, which may result in alternative stable states where some populations are resistant and others are tolerant. Intraspecific variation in immune costs is rarely surveyed in a manner that tests evolutionary patterns, and there are few examples of adaptive loss of resistance. Here, we show that when marine threespine stickleback colonized freshwater lakes, they gained resistance to the freshwater-associated cestode Schistocephalus solidus. Extensive peritoneal fibrosis and inflammation are a commonly observed phenotype that contributes to suppression of cestode growth and viability but also imposes a substantial cost on fecundity. Combining genetic mapping and population genomics, we find that opposing selection generates immune system differences between tolerant and resistant populations, consistent with divergent optimization.
DOI: abo3411
Source: https://www.science.org/doi/10.1126/science.abo3411