PDF(Pubmed)
Abstract：
Body size may drive the molecular evolution of mitochondrial genes in response to changes in energy requirements across species of different sizes. In this study, we perform selection pressure analysis and phylogenetic independent contrasts (PIC) to investigate the association between molecular evolution of mitochondrial genome protein-coding genes (mtDNA PCGs) and body size in terrestrial Cetartiodactyla. Employing selection pressure analysis, we observe that the average non-synonymous/synonymous substitution rate ratio (ω) of mtDNA PCGs is significantly reduced in small-bodied species relative to their medium and large counterparts. PIC analysis further confirms that ω values are positively correlated with body size (R2 = 0.162, p = 0.0016). Our results suggest that mtDNA PCGs of small-bodied species experience much stronger purifying selection as they need to maintain a heightened metabolic rate. On the other hand, larger-bodied species may face less stringent selective pressures on their mtDNA PCGs, potentially due to reduced relative energy expenditure per unit mass. Furthermore, we identify several genes that undergo positive selection, possibly linked to species adaptation to specific environments. Therefore, despite purifying selection being the predominant force in the evolution of mtDNA PCGs, positive selection can also occur during the process of adaptive evolution.
摘要：
身体大小可能会驱动线粒体基因的分子进化，以响应不同大小物种之间能量需求的变化。在这项研究中,我们进行选择压力分析和系统发育独立对比（PIC），以研究线粒体基因组蛋白质编码基因（mtDNAPCGs）的分子进化与陆生牛耳体型之间的关联。采用选择压力分析，我们观察到mtDNAPCGs的平均非同义/同义取代率比率(ω)在小型物种中相对于中型和大型物种显著降低.PIC分析进一步证实ω值与体型呈正相关(R2=0.162,p=0.0016)。我们的结果表明，小型物种的mtDNAPCG经历了更强的纯化选择，因为它们需要保持更高的代谢率。另一方面,体型较大的物种可能会对其mtDNAPCGs面临不太严格的选择压力，可能是由于单位质量的相对能量消耗减少。此外，我们确定了几个经历正选择的基因，可能与物种对特定环境的适应有关。因此,尽管纯化选择是mtDNAPCGs进化的主导力量，在适应性进化过程中也会发生正向选择。
