Haag Christoph R, Hottinger Jürgen W, Riek Myriam, Ebert Dieter
Universität Basel, Zoologisches Institut, Switzerland.
Evolution. 2002 Mar;56(3):518-26.
The deleterious effects of inbreeding have long been known, and inbreeding can increase the risk of extinction for local populations in metapopulations. However, other consequences of inbreeding in metapopulations are still not well understood. Here we show the presence of strong inbreeding depression in a rockpool metapopulation of the planktonic freshwater crustacean Daphnia magna, which reproduces by cyclical parthenogenesis. We conducted three experiments in real and artificial rockpools to quantify components of inbreeding depression in the presence and the absence of competition between clonal lines of selfed and outcrossed genotypes. In replicated asexual populations, we recorded strong selection against clones produced by selfing in competition with clones produced by outcrossing. In contrast, inbreeding depression was much weaker in single-clone populations, that is, in the absence of competition between inbred and outbred clones. The finding of a competitive advantage of the outbred genotypes in this metapopulation suggests that if rockpool populations are inbred, hybrid offspring resulting from crosses between immigrants and local genotypes might have a strong selective advantage. This would increase the effective gene flow in the metapopulation. However, the finding of low inbreeding depression in the monoclonal populations suggests that inbred and outbred genotypes might have about equal chances of establishing new populations.
近亲繁殖的有害影响早已为人所知，而且近亲繁殖会增加集合种群中局部种群灭绝的风险。然而，集合种群中近亲繁殖的其他后果仍未得到很好的理解。在此，我们展示了在浮游淡水甲壳动物大型溞的岩池集合种群中存在强烈的近亲繁殖衰退现象，大型溞通过周期性孤雌生殖进行繁殖。我们在真实和人工岩池中进行了三项实验，以量化在自交和杂交基因型的克隆系之间存在和不存在竞争的情况下近亲繁殖衰退的组成部分。在重复的无性繁殖种群中，我们记录到在与杂交产生的克隆系竞争时，对自交产生的克隆系存在强烈的选择淘汰。相比之下，在单克隆种群中，即近亲繁殖和非近亲繁殖的克隆系之间不存在竞争时，近亲繁殖衰退要弱得多。在这个集合种群中发现杂交基因型具有竞争优势，这表明如果岩池种群是近亲繁殖的，那么移民与本地基因型杂交产生的杂交后代可能具有很强的选择优势。这将增加集合种群中的有效基因流动。然而，在单克隆种群中发现近亲繁殖衰退程度较低，这表明近亲繁殖和非近亲繁殖的基因型建立新种群的机会可能大致相等。
