Date Published: February 13, 2017
Publisher: Public Library of Science
Author(s): Nohelia Farías-Curtidor, Dalia C. Barragán-Barrera, Paula Alejandra Chávez-Carreño, Cristina Jiménez-Pinedo, Daniel M. Palacios, Dalila Caicedo, Fernando Trujillo, Susana Caballero, Chaolun Allen Chen.
The nearest known population of common dolphins (Delphinus sp.) to the Colombian Caribbean occurs in a fairly restricted range in eastern Venezuela. These dolphins have not been previously reported in the Colombian Caribbean, likely because of a lack of study of the local cetacean fauna. We collected cetacean observations in waters of the Guajira Department, northern Colombia (~11°N, 73°W) during two separate efforts: (a) a seismic vessel survey (December 2009—March 2010), and (b) three coastal surveys from small boats (May—July 2012, May 2013, and May 2014). Here we document ten sightings of common dolphins collected during these surveys, which extend the known range of the species by ~1000 km into the southwestern Caribbean. We also collected nine skin biopsies in 2013 and 2014. In order to determine the taxonomic identity of the specimens, we conducted genetic barcoding and phylogenetic analyses using two mitochondrial markers, the Control Region (mtDNA) and Cytochrome b (Cytb). Results indicate that these specimens are genetically closer to the short-beaked common dolphin (Delphinus delphis) even though morphologically they resemble a long-beaked form (Delphinus sp.). However, the specific taxonomic status of common dolphins in the Caribbean and in the Western Atlantic remains unresolved. It is also unclear whether the distribution of the species between northern Colombia and eastern Venezuela is continuous or disjoined, or whether they can be considered part of the same stock.
Common dolphins (genus Delphinus) are widely distributed in all tropical and temperate oceans around the world. However, details of their distribution are not well described because until 1994 all common dolphins were regarded as single species, D. delphis, despite knowledge of the existence of long-beaked and short-beaked morphotypes [1, 2]. Morphological features that include body coloration, teeth number, vertebral number and the rostral length: zygomatic width ratio, and genetic comparisons between long-beaked and short beaked morphotypes using mitochondrial markers in the Eastern North Pacific established the long-beaked morphotype as D. capensis, a separate species from the short-beaked morphotype, D. delphis [1, 3]. Nevertheless, the separation of the genus Delphinus into a short-beaked and a long-beaked species on a global scale is not clear under these morphological, phylogenetic, and genetic evidence, and therefore taxonomy of this species remains controversial [4, 5, 6, 7, 8].
Recent survey work in a previously unexplored area of the Colombian Caribbean in 2010, 2012, 2013, and 2014 has yielded ten sightings of the common dolphin, a new species record for the country. These sightings also extend the known distribution range of the species to the southwestern Caribbean and provide new information on their local distribution and external appearance. The global distribution of common dolphins largely coincides with temperate and tropical coastal areas influenced by wind-driven upwelling . In this respect the occurrence of common dolphins off the Guajira Peninsula is not unexpected, as the area is known for persistent upwelling and high productivity [49, 50, 51, 52, 53, 54].