Data from: No evidence for extrinsic post-zygotic isolation in a wild Saccharomyces yeast system

Although microorganisms account for the largest fraction of Earth's biodiversity, we know little about how their reproductive barriers evolve. Sexual microorganisms such as Saccharomyces yeasts rapidly develop strong intrinsic post-zygotic isolation, but the role of extrinsic isolation in the early speciation process remains to be investigated. We measured the growth of F1 hybrids between two incipient species of Saccharomyces paradoxus to assess the presence of extrinsic post-zygotic isolation across 32 environments. More than 80% of hybrids showed either partial dominance of the best parent or over-dominance for growth, revealing no fitness defects in F1 hybrids. Extrinsic reproductive isolation therefore likely plays little role in limiting gene flow between incipient yeast species and is not a requirement for speciation.

尽管微生物占据了地球生物多样性的最大份额，但我们对其生殖屏障的演化过程仍知之甚少。有性生殖的微生物如酵母菌属（Saccharomyces）酵母可快速形成强固的内在合子后生殖隔离（intrinsic post-zygotic isolation），但外在隔离在物种形成早期进程中的作用仍有待探究。我们以两种处于物种形成初期的帕氏酿酒酵母（Saccharomyces paradoxus）的F1杂交子代作为研究材料，检测其在32种不同环境下的生长表现，以此评估外在合子后生殖隔离的存在与否。超过80%的杂交子代在生长性状上表现出最优亲本的部分显性或超显性特征，表明F1杂交子代并未出现适合度缺陷。由此可见，外在生殖隔离在限制初期酵母物种间的基因流动方面作用甚微，且并非物种形成的必要条件。