Genômica da origem híbrida do golfinho Stenella Clymene

Abstract

Hybridization has been shown to be much more prevalent in animal than previously thought, in special with the increasing use of genomic data. It has been suggested recently, based on morphological and molecular (mtDNA and few nuclear loci) data that the Clymene Dolphin, Stenella clymene, originated from the hybridization between Stenella longirostris and Stenella coeruleoalba. Here we use the whole-nuclear and mitochondrial genomes of these species plus three other delphinines to test this hypothesis and reconstruct their evolutionary history. A highly supported nuclear genome species tree shown that S. clymene and S. longirostris are sister species as well as S. coeruleoalba and T. truncatus, located in two different clades. In contrast, in mtDNA genome phylogeny S. longirostris and S. coeruleoalba switched position, in which S. coeruleoalba is sister to S. clymene, and S. longirostris is closer to T. truncatus. Admixture analyses shown no evidence of S. clymene as a hybrid species, but we found strong evidence of an introgression event in which about 40% of the genome of the ancestor of S. clymene and S. longirostris came from S. coeruleoalba. These results and the pattern of mito-nuclear discordance suggest a bidirectional but sex (female)-biased introgression that completely replaced (exchanged) the original mitochondrial genomes of S. longirostris and S. coeruleoalba. We find evidence of introgression (13%) of the ancestral of S. longirostris, S. clymene and D. delphis into S. coeruleoalba and a very small (1.4%) level of introgression of S. frontalis into S. longirostris.