Mitochondrial DNA supports the low genetic diversity of Tursiops truncatus (Artiodactyla: Delphinidae) in Bocas del Toro, Panama and exhibits new Caribbean haplotypes

Abstract

Introduction: The common bottlenose dolphin (Tursiops truncatus) is one of the most studied cetaceans worldwide; however, information about the genetic structure of wild populations is scarce in some regions like Central America and the Caribbean. There are two known genetic forms identified in the Caribbean based on mitochondrial DNA Control Region (mtDNA-CR) data: the ‘inshore (or coastal) form’ and the ‘Worldwide distributed form’. In general, the inshore form refers to coastal and highly philopatric populations that show low genetic diversity. Worldwide distributed form refers to highly mobile populations with coastal and oceanic individuals that do not show philopatry and usually display high genetic diversity.
 Objective: To determine the preliminary genetic status of common bottlenose dolphins in La Guajira, Colombian Caribbean, using a hypervariable portion of mtDNA-CR. The obtained haplotypes were compared with samples collected in Panama (likely ‘inshore form’) and with haplotypes previously found in other areas of the Caribbean.
 Methods: In 2016, a total of 26 skin samples were obtained by remote biopsy system (PAXARMS) in two locations, La Guajira (Colombia, N=7) and Bocas del Toro (Panama, N=19). DNA was extracted, samples sexed, and a segment of mtDNA-CR (~550-750 bp) was amplified by PCR. The successfully amplified DNA sequences were manually reviewed and cleaned, and subsequently compared with 44 haplotypes previously reported for the Caribbean.
 Results: The mtDNA-CR sequences from Bocas del Toro shared the same unique inshore haplotype previously reported for this population, while the samples from La Guajira represented six novel haplotypes, five belonging to the Worldwide distributed form and one to the ‘inshore form.’ Population structure analysis revealed two phylogroups for the Caribbean (FST=0.1353, ΦST=0.3330) with high haplotype diversity: Panama(Bocas del Toro)-Bahamas-Cuba-Mexico (h=0.8489, π=4.2536 %) and Colombia-Costa Rica-Honduras-Puerto Rico (h=0.8837, π=4.2423 %).
 Conclusions: These findings support the results previously reported for common bottlenose dolphins in Bocas del Toro-Panama and reinforce the need to protect this vulnerable ‘inshore’ population by treating it as a unique population management unit. Mitochondrial DNA analysis of samples collected from La Guajira dolphins provide the first insight into the genetic diversity of common bottlenose dolphins in this region, indicating the presence of both inshore and Worldwide distributed genetic forms. The potential connectivity of this last form among La Guajira-Colombia, Costa Rica, and Honduras in Central America highlights the need for more genetic and ecological studies to determine the appropriate management units for this species in Central America and the Caribbean.