School of Life and Environmental Sciences, University of Sydney, Sydney, New South Wales, Australia.
Ecology & Evolution, Research School of Biology, Australian National University, Acton, Australian Capital Territory, Australia.
Proc Biol Sci. 2024 May;291(2023):20232439. doi: 10.1098/rspb.2023.2439. Epub 2024 May 22.
Genetic changes that enabled the evolution of eusociality have long captivated biologists. More recently, attention has focussed on the consequences of eusociality on genome evolution. Studies have reported higher molecular evolutionary rates in eusocial hymenopteran insects compared with their solitary relatives. To investigate the genomic consequences of eusociality in termites, we analysed nine genomes, including newly sequenced genomes from three non-eusocial cockroaches. Using a phylogenomic approach, we found that termite genomes have experienced lower rates of synonymous substitutions than those of cockroaches, possibly as a result of longer generation times. We identified higher rates of non-synonymous substitutions in termite genomes than in cockroach genomes, and identified pervasive relaxed selection in the former (24-31% of the genes analysed) compared with the latter (2-4%). We infer that this is due to reductions in effective population size, rather than gene-specific effects (e.g. indirect selection of caste-biased genes). We found no obvious signature of increased genetic load in termites, and postulate efficient purging of deleterious alleles at the colony level. Additionally, we identified genomic adaptations that may underpin caste differentiation, such as genes involved in post-translational modifications. Our results provide insights into the evolution of termites and the genomic consequences of eusociality more broadly.
使真社会性得以进化的遗传变化长期以来一直吸引着生物学家的注意。最近，人们的注意力集中在真社会性对基因组进化的影响上。研究报告称，与独居的亲缘物种相比，真社会性膜翅目昆虫的分子进化率更高。为了研究白蚁真社会性的基因组后果，我们分析了 9 个基因组，包括 3 种非真社会性蟑螂的新测序基因组。我们利用系统基因组学方法发现，白蚁的基因组经历的同义替换率比蟑螂的要低，这可能是由于其世代时间较长。我们发现白蚁的基因组中非同义替换率高于蟑螂的，并且前者（分析的基因的 24%-31%）比后者（2%-4%）普遍存在松弛选择。我们推断这是由于有效种群大小的减少，而不是基因特异性效应（例如，对具社会分工基因的间接选择）。我们没有发现白蚁中有明显的遗传负荷增加的迹象，而是假设在群体水平上可以有效地清除有害等位基因。此外，我们还发现了可能支持级型分化的基因组适应，例如参与翻译后修饰的基因。我们的研究结果为白蚁的进化和更广泛的真社会性的基因组后果提供了深入的了解。
