Adaptive evolution of β-globin gene in subterranean in South America octodontid rodents

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.

Automated summary

The convergent evolution of subterranean rodents is a valuable model for studying natural selection and genetic adaptations. Different approaches have identified three sites with evidence of positive selection in underground lineages, especially in the basal branch leading to the Octodontidae family and the branch leading to the coruro, suggesting adaptive changes in response to underground life. Additionally, there is evidence of convergence with another underground rodent that cannot be identified using traditional methods.