Department of Ecology and Evolution, Université de Lausanne, Lausanne, Switzerland.
Vital-IT, Swiss Institute of Bioinformatics, Lausanne, Switzerland.
J Evol Biol. 2018 Sep;31(9):1413-1419. doi: 10.1111/jeb.13336. Epub 2018 Jul 6.
The recent advances of new genomic technologies have enabled the identification and characterization of sex chromosomes in an increasing number of nonmodel species, revealing that many plants and animals undergo frequent sex chromosome turnovers. What evolutionary forces drive these turnovers remains poorly understood, but it was recently proposed that drift might play a more important role than generally assumed. We analysed the dynamics of different types of turnovers using individual-based simulations and show that when mediated by genetic drift, turnovers are usually easier to achieve than substitutions at neutral markers, but that their dynamics and relative likelihoods vary with the type of the resident and emergent sex chromosome system (XY and/or ZW) and the dominance relationships among the sex-determining factors. Focusing on turnovers driven by epistatically dominant mutations, we find that drift-mediated turnovers that preserve the heterogamety pattern are 2-4× more likely than those along which the heterogametic sex changes. This ratio nevertheless decreases along with effective population size and can even reverse in case of extreme polygyny. This can be attributed to a 'drift-induced' selective force, known to influence transitions between male and female heterogamety, but which according to our study does not affect turnovers that preserve the heterogametic sex.
新基因组技术的最新进展使得越来越多的非模式物种的性染色体得以被识别和描述，揭示出许多植物和动物经历了频繁的性染色体倒位。是什么进化力量驱动了这些倒位仍然知之甚少，但最近有人提出，漂变可能比人们通常认为的更为重要。我们使用基于个体的模拟分析了不同类型的倒位的动态，结果表明，当由遗传漂变介导时，倒位通常比中性标记的替代更容易实现，但它们的动态和相对可能性因驻留和新兴的性染色体系统（XY 和/或 ZW）的类型以及性别决定因素之间的优势关系而有所不同。我们专注于由上位显性突变驱动的倒位，发现漂变介导的保持异配子型模式的倒位比那些改变异配子性别的倒位的可能性高 2-4 倍。然而，这个比例随着有效种群大小的减少而减少，并且在极端多配偶制的情况下甚至会逆转。这可以归因于一种“漂变诱导”的选择力，已知这种选择力会影响雄性和雌性异配子型之间的转变，但根据我们的研究，这种选择力不会影响保持异配子性的倒位。
