Kumar Nikesh M, Cooper Taylor L, Kocher Thomas D, Streelman J Todd, McGrath Patrick T
School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA.
Department of Biology, University of Maryland, College Park, MD USA.
bioRxiv. 2025 Mar 18:2024.10.28.620687. doi: 10.1101/2024.10.28.620687.
Chromosomal inversions are an important class of genetic variation that link multiple alleles together into a single inherited block that can have important effects on fitness. To study the role of large inversions in the massive evolutionary radiation of Lake Malawi cichlids, we used long-read technologies to identify four single and two tandem inversions that span half of each respective chromosome, and which together encompass over 10% of the genome. Each inversion is fixed in one of the two states within the seven major ecogroups, suggesting they played a role in the separation of the major lake lineages into specific lake habitats. One exception is within the sub-radiation, where both inverted and non-inverted alleles continue to segregate within the group. The evolutionary histories of three of the six inversions suggest they transferred from the pelagic group into ancestors at the time the sub-radiation was seeded. The remaining three inversions are found in a subset of species living in deep waters. We show that some of these inversions are used as XY sex-determination systems but are also likely limited to a subset of total lake species. Our work suggests that inversions have been under both sexual and natural selection in Lake Malawi cichlids and that they will be important to understanding how this adaptive radiation evolved.
染色体倒位是一类重要的遗传变异，它将多个等位基因连接成一个单一的遗传模块，这可能对适应性产生重要影响。为了研究大型倒位在马拉维湖丽鱼科鱼类大规模进化辐射中的作用，我们使用长读长技术识别出四个单倒位和两个串联倒位，它们分别跨越每条染色体的一半，总共覆盖超过10%的基因组。每个倒位在七个主要生态类群中的两种状态之一中是固定的，这表明它们在主要湖泊谱系分离到特定湖泊栖息地的过程中发挥了作用。一个例外是在亚辐射类群中，其中倒位和非倒位等位基因在该类群中继续分离。六个倒位中的三个的进化历史表明，在亚辐射类群形成时，它们从浮游类群转移到了祖先中。其余三个倒位存在于生活在深水区域的一部分物种中。我们表明，其中一些倒位被用作XY性别决定系统，但也可能仅限于整个湖泊物种的一个子集。我们的研究表明，倒位在马拉维湖丽鱼科鱼类中受到性选择和自然选择的影响，并且它们对于理解这种适应性辐射是如何进化的将是重要的。
