The convergent evolution of subterranean rodents is an excellent model to study how natural selection operates and the genetic bases of these adaptations, but the study on the different taxa has been very uneven and still insufficient. In the octodontoid caviomorph rodent superfamily there are two independent lineages where they have recently evolved into totally underground lifestyles: the genera Ctenomys (tuco-tucos) and Spalacopus (coruro). The underground habitat is characterized by an hypoxic and hypercapnic atmosphere, thus gas exchange is one of the most important challenges for these animals. The invasion of the underground niche could have modified the selective regimes of proteins involved in the respiration and transport of O₂ of these rodents, positively selecting mutations of higher affinity for O₂. Here we examine the sequence variation in the beta globin gene in these two lineages, within a robust phylogenetic context. Using different approaches (classical and Bayesian maximum likelihood (PAML/Datamonkey) and alternatives methods (TreeSAAP)) we found at least three sites with evidence of positive selection in underground lineages, especially the basal branch that leads to the Octodontidae family and the branch that leads to the coruro, suggesting some adaptive changes to the underground life. We also found a convergence with another underground rodent, which cannot be identified by the above methods.

地下啮齿动物的趋同进化是研究自然选择如何运作以及这些适应的遗传基础的极佳模型，但是对不同分类单元的研究非常不平衡，仍然不足。在octodontoid豚鼠小目啮齿动物家族有两个独立的谱系，他们最近已经演变成完全地下的生活方式：该属Ctenomys（图科-tucos）和Spalacopus（鼢足鼠）。地下栖息地的特点是低氧和高碳酸血症，因此气体交换对这些动物来说是最重要的挑战之一。地下生态位的入侵可能会改变参与O ₂呼吸和运输的蛋白质的选择性机制这些啮齿动物中，积极选择对O ₂具有更高亲和力的突变。在这里，我们在稳健的系统发育背景下研究了这两个谱系中β珠蛋白基因的序列变异。使用不同的方法（经典和贝叶斯最大似然法（PAML / Datamonkey）和替代方法（TreeSAAP）），我们发现了至少三个在地下谱系中具有阳性选择证据的位点，尤其是导致八爪鱼科的基础分支和导致天蓝色，暗示地下生活有一些适应性变化。我们还发现与另一只地下啮齿类动物会聚，但上述方法无法确定。