Padrões de diversidade, diferenciação e hibridação no gênero Stenella

Abstract

Stenella is a genus of the Delphinidae family composed by five species of cricum-tropical distribution, with the exception of S. clymene and S. frontalis, endemic to the Atlantic Ocean. This genus is paraphyletic, whose taxonomic classification and phylogenetic relationships are considered confusing and possibly reflect the recent divergence (about three million years) and hybridization events between species. The aim of this thesis was to test the hypothesis of hybridization among species of the genus Stenella and to evaluate the genetic diversity and differentiation of one species, Stenella longirostris. Using mitochondrial molecular markers, strong evidence of hybridization between S. clymene and S. coeruleoalba species has been demonstrated, which reinforces that this process may be one of those responsible for the complex taxonomy of the group. No signs of mixing were found for S. longirostris, S. attenuata and S. frontalis, and monophyletic clades were observed for those species. It was shown that individuals of S. longirostris from the Fernando de Noronha Archipelago (islands-associated) compose a population with low genetic diversity and high genetic isolation from other populations of the world. Besides this population, the presence of another population formed by individuals sampled along the Brazilian coast (nonassociated-islands) was displayed. It was also shown that the two populations of southwestern Atlantic Ocean are highly differentiated from all populations in other parts of the world, especially the Pacific Ocean. In addition, it was evident the low genetic diversity and high differentiation of the spinner dolphins of the Hawaiian Islands. These results suggest a metapopulation dynamics with dispersion or periodic interchange among populations geographically distant from different ocean basins, and, high site fidelity to suitable island habitats.