Insight into the Evolution of Mitochondrial Genetic Basis of Amphibious Adaptation in the Goby (Teleostei: Gobiidae).

The adaptation to terrestrial environments from aquatic environments has always been regarded as a major evolutionary transition in fishes, during which it has been accompanied with diverse phenotypic innovations. Mitochondrial energy metabolism fundamentally enables this shift, but the evolutionary trajectory and molecular mechanisms of mitogenomic adaptations to energy demands are poorly characterized. Mudskippers, a group of gobies with amphibious adaptive traits, serve as ideal models for studying energy metabolism during the water-to-land transition. To test whether amphibious adaptation in gobies corresponds to adaptive evolution in mitochondrial OXPHOS genes, we performed an in silico analysis of the 13 OXPHOS genes from the mitochondrial genomes of 33 goby species and two outgroups. The results showed that: (1) No matter ML or BI methods, four subfamilies Amblyopinae, Gobiinae, Gobionellinae, Oxudercinae are paraphyletic origin, except for subfamily Sicydiinae; besides, genus Scartelaos was first confirmed that it is paraphyletic origin. (2) 13 OXPHOS genes have been under the strong selective constraints, yet, the episodic positive selection was also detected, and ND4 and ATP8 evolution has been found to be under the accelerated evolution. Interestingly, (3) Significant divergent selection was detected between amphibious and fully aquatic lineages in 11 of the 13 OXPHOS genes (84%). And (4) the much stronger selective constraints were uncovered in amphibious lineages. To sum up, OXPHOS genes have undergone adaptive evolution with notable divergent patterns associated with the water-to-land transition during transition from water to land. These results provided some new insights into the genetic basis of amphibious adaptation in goby.