Molecular and morphological differentiation of common dolphins (Delphinus sp.) in the Southwestern Atlantic: testing the two species hypothesis in sympatry

CUNHA, H.A; R LOIZAGA DE CASTRO; E.R. SECCHI; E.A. CRESPO; J. LAILSON-BRITO; A.F. AZEVEDO; C. LAZOSKI; A.M. SOLÉ-CAVA

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2015

1932-6203

The taxonomy of common dolphins (Delphinus sp.) has always been controversial, with over twenty described species since the original description of the type species of the genus (Delphinus delphis Linnaeus, 1758). Two species and four subspecies are currently accepted, but recent molecular data have challenged this view. In this study we investigated the molecular taxonomy of common dolphins through analyses ofcytochrome b sequences of 297 individuals from most of their distribution. We included 37 novel sequences from the Southwestern Atlantic, a region where the short and long-beaked morphotypes occur in sympatry, but which had not been well sampled before. Skulls from individuals of the two morphotypes were also measured to test the validity of the rostral index as a diagnostic character, as proposed by Heyning & Perrin [1]. Our genetic results show that all common dolphins in the Atlantic Ocean belong to a single species, Delphinus delphis. According to genetic data, the species Delphinus capensis is invalid. Long-beaked common dolphins from the Northeastern Pacific may constitute a different species, but the tropicalis-form apparently does not deserve subspecific status. Our conclusions prompt the need for revision of currently accepted common dolphin species and subspecies, and of Delphinus delphis distribution.