Adaptive changes may be caused by various mechanisms of gene evolution. Some studies suggest that changes in gene expression often result in adaptive evolution of regulatory sequences [17]. However, changes in coding sequence most certainly lead to evolutionary transitions as well [18–20]. Another mechanism of evolution is expansion or contraction of gene families. It is suggested that gene gain or loss is a major source of novel gene functions and evolutionary innovation, since it provides opportunities for specific adaptations [21–23]. Although most new genes originate by duplication of preexisting genes [24, 25], new protein-coding genes could also evolve de novo out of non-coding sequences