Resumen

Gene duplication followed by adaptive divergence is an important source of molecular novelty and thus evolutionary innovation. Gene duplication followed by neofunctionalization can create a tension between natural selection favoring the new function and non-allelic gene conversion (NAGC) restoring the ancestral sequence, as demonstrated recently for the Na+,K+-ATPase ¿1 subunit (ATP1A1) paralog in the frog genus, Leptodactylus. Here we sought to evaluate the potential generality of this previous example. We examined newly available amphibian genome and transcriptome assemblies for possible duplications of ATP1A1. We confirmed the existence of a tandem ATP1A1 duplication in Ranitomeya imitator and a potentially tandem duplication in Oophaga pumilio, in the family Dendrobatidae. In both cases, one of the ATP1A1 paralogs evolved to allow resistance to cardiotonic steroids, while the other retained ancestral susceptibility. Within species, frequent NAGC homogenized most of the sequence between the two copies but was countered by strong selection on 5 amino acid substitutions distinguishing the two paralogs. We documented a ATP1A1 duplication in R. imitator and O. pumilio and there are no other documented examples in any tetrapods, besides Leptodactylus. Our results show that important resistant cardiotonic substitutions are being maintained by positive selection.