Signature of selection on the rhodopsin gene in the marine radiation of American seven-spined gobies (Gobiidae, Gobiosomatini).

In comparison with terrestrial and freshwater ecosystems, information about speciation modes and the role of selection in marine environments is scarce. Recent studies have indicated that spectral adaptation could play an important role in the diversification of marine species flocks. Natural selection influences specific amino acids (AAs) that are involved in the spectral tuning mechanism of visual pigment genes. To study the wider occurrence and the characteristics of spectral adaptation in marine radiations, a reinterpretation of the rhodopsin (RH1) data of American seven-spined gobies (genus Elacatinus; Gobiidae; Teleostei) was carried out. Reanalysis revealed that some AAs, which are well known in the literature as spectral tuning sites, are variable in Elacatinus. Those crucial AA substitutions originated polyphyletically, indicating convergent evolution within the genus Elacatinus. Moreover, statistical tests based on the d(N)/d(S) ratio detected selection in several phylogenetic lineages and at specific AAs. Many of these AAs were previously shown to be under selection in other marine radiations. Therefore, the current phylogenetic approach provided an extended list of AAs that are probably involved in spectral tuning, and which should be validated by mutagenic experiments.