Origine, Structure, Evolution de la Biodiversité, UMR 7205 CNRS-MNHN, Muséum National d'Histoire Naturelle, Paris, France.
J Evol Biol. 2013 Sep;26(9):1968-78. doi: 10.1111/jeb.12196. Epub 2013 Jul 13.
Why sexual reproduction is so prevalent in nature remains a major question in evolutionary biology. Most of the proposed advantages of sex rely on the benefits obtained from recombination. However, it is still unclear whether the conditions under which these recombinatorial benefits would be sufficient to maintain sex in the short term are met in nature. Our study addresses a largely overlooked hypothesis, proposing that sex could be maintained in the short term by advantages due to functions linked with sex, but not related to recombination. These advantages would be so essential that sex could not be lost in the short term. Here, we used the fungus Aspergillus nidulans to experimentally test predictions of this hypothesis. Specifically, we were interested in (i) the short-term deleterious effects of recombination, (ii) possible nonrecombinatorial advantages of sex particularly through the elimination of mutations and (iii) the outcrossing rate under choice conditions in a haploid fungus able to reproduce by both outcrossing and haploid selfing. Our results were consistent with our hypotheses: we found that (i) recombination can be strongly deleterious in the short term, (ii) sexual reproduction between individuals derived from the same clonal lineage provided nonrecombinatorial advantages, likely through a selection arena mechanism, and (iii) under choice conditions, outcrossing occurs in a homothallic species, although at low rates.
为什么有性繁殖在自然界中如此普遍，这仍然是进化生物学中的一个主要问题。大多数关于性的优势的假设都依赖于从重组中获得的好处。然而，目前还不清楚在自然条件下，这些重组优势是否足以维持短期的性。我们的研究提出了一个很大程度上被忽视的假设，即性可以通过与性相关的功能而不是与重组相关的功能来维持短期优势。这些优势将是如此重要，以至于在短期内无法失去性。在这里，我们使用真菌构巢曲霉来实验验证这一假设的预测。具体来说，我们感兴趣的是：（i）重组的短期有害影响，（ii）性的可能非重组优势，特别是通过消除突变，以及（iii）在能够通过杂交和单性生殖进行繁殖的单倍体真菌中，在选择条件下的杂交率。我们的结果与假设一致：我们发现（i）重组在短期内可能是非常有害的，（ii）来自同一克隆谱系的个体之间的有性繁殖提供了非重组优势，可能是通过选择竞技场机制，以及（iii）在选择条件下，杂交发生在同宗配合的物种中，尽管杂交率很低。
