Genetic diversity and population structure in four species of cetaceans around the Mariana Islands

"Relatively little is known about cetaceans inhabiting the waters of the Mariana Islands in the western Pacific. We use mitochondrial DNA (mtDNA) sequences obtained from biopsy samples to investigate the genetic diversity and structure of four species of delphinids found near the Mariana Islands-short-finned pilot whales (SFPWs; Globicephala macrorhynchus ; n=47), spinner dolphins (Stenella longirostris longirostris ; n= 95), bottlenose dolphins (Tursiops truncatus ; n=15), and melon-headed whales (MHWs; Peponocephala electra ; n=2). We found evidence of genetic differentiation between islands for SFPWs, but not for spinner dolphins. Sample sizes were too small to investigate differentiation within the other two species. SFPWs around the Marianas possess haplotypes also common in the South Pacific, North Atlantic, Indian Ocean, and off of southern Japan. Both spinner dolphins and MHWs possess haplotypes common throughout the Pacific. The spinner dolphins exhibit high haplotypic diversity similar to that observed in the Society Islands of French Polynesia, suggesting they are not as genetically isolated as Hawaiian spinner dolphins. We did not find any T. aduncus haplotypes among the bottlenose dolphin samples, instead finding that two-thirds of the animals possess T. truncatus haplotypes while the remaining one-third share a single Fraser's dolphin (Lagenodlephis hosei) haplotype. Photo-identification data confirm that the five samples with Fraser's dolphin haplotypes come from five different individuals, all of which appear morphologically to be bottlenose dolphins. This result suggests that there has been extensive introgression of Fraser's dolphin mtDNA into the Mariana Islands bottlenose dolphin gene pool." Karen K. Martien, Marie C. Hill, Amy M. Van Cise, Kelly M. Robertson, Samuel M. Woodman, Louella Dolar, Victoria L. Pease, and Erin M. Oleson. "August 2014." System requirements: Adobe Acrobat Reader. Includes bibliographical references (pages 12-14).