Coevolutionary interactions with parasites constrain the spread of self-fertilization into outcrossing host populations

Given the cost of sex, outcrossing populations should be susceptible to invasion and replacement by self-fertilization or parthenogenesis. However, biparental sex is common in nature, suggesting that cross-fertilization has substantial short-term benefits. The Red Queen hypothesis (RQH) suggests that coevolution with parasites can generate persistent selection favoring both recombination and outcrossing in host populations. We tested the prediction that coevolving parasites can constrain the spread of self-fertilization relative to outcrossing. We introduced wild-type Caenorhabditis elegans hermaphrodites, capable of both self-fertilization, and outcrossing, into C. elegans populations that were fixed for a mutant allele conferring obligate outcrossing. Replicate C. elegans populations were exposed to the parasite Serratia marcescens for 33 generations under three treatments: a control (avirulent) parasite treatment, a fixed (nonevolving) parasite treatment, and a copassaged (potentiall...鉴于有性生殖存在进化代价，异交种群（outcrossing populations）理应易受自交（self-fertilization）或孤雌生殖（parthenogenesis）个体的入侵与替代。但双亲有性生殖（biparental sex）在自然界中仍广泛存在，这表明异体受精（cross-fertilization）具备显著的短期进化优势。红皇后假说（Red Queen hypothesis, RQH）提出，宿主种群与寄生虫（parasites）的协同进化可产生持续的选择压力，促使宿主同时偏好重组与异交。我们验证了“相较于异交，协同进化的寄生虫可限制自交传播”这一预测。我们将兼具自交与异交能力的野生型秀丽隐杆线虫（Caenorhabditis elegans）雌雄同体，引入到携带专性异交（obligate outcrossing）突变等位基因（mutant allele）的秀丽隐杆线虫种群中。将重复秀丽隐杆线虫种群置于三种处理条件下，暴露于粘质沙雷氏菌（Serratia marcescens）共33个世代：分别为无毒性寄生虫对照处理组、固定（非进化型）寄生虫处理组，以及共传代（潜在……