DNA Barcoding of Kemp’s Ridley (Lepidochelys kempii) in México ^†

Abstract

From the seven existing species of sea turtles, two are endemic to Mexico and one of these inhabits the Gulf of Mexico and nests mainly in the Rancho Nuevo (RN) Sanctuary, Aldama, Tamaulipas, Mexico [1]. There are other important beaches in Tamaulipas, Mexico, as Tepehuajes (TEP), Barra del Tordo (BdT), Altamira (ALT), y Miramar (MIR) and outside Mexico in South Padre Island (SPI), TX, USA, all locations in the Gulf of Mexico. The objective of this work was to determine the DNA barcode by COI gene sequences in Kemp’s ridley sea turtle (Lepidochelys kempii) and to estimate their genetic divergence. One hundred and one new sequences were obtained from the Kemp’s ridley turtles from the RN sanctuary and compared with the 13 sequences reported in BOLD database [2]. Sequences of nearly 700 bp of Kemp’s ridley were aligned among them and compared to seven different sea turtle species; all new sequences will be added to the BOLD database. Genetic divergence showed a clear separation between other species (0.02 to 0.12), while their relationship with the olive ridley sea turtle (Lepidochelys olivacea) was confirmed (0.02). Additionally, the result of the haplotype network showed five haplotypes, four out of which were novel and only one was the most predominant, it belonged to RN sanctuary, the second one was LK-COI-01 previously reported [3], mostly all sequences were grouped from outside Mexico and only one was from BdT. Finally, the other three ones (twice sequenced) were described for only one sequence each (MIR, ALT, and TEP). Furthermore, the phylogenetic tree showed and confirmed the separation into two main clades, or families, and one out of them, contained the remaining six sea turtle species. Finally, the DNA barcode for Kemp’s ridley was obtained [4]. In conclusion, the main haplotype corresponded to RN Sanctuary as it was expected, and the secondary camps are part of the RN Sanctuary as they are around less than 100 km distant. There was clear evidence that DNA barcode by the COI gene is useful for the study of Kemp’s ridley turtles, being able to discriminate between dominant and new haplotypes from those already reported, as well as study phylogeny and genetic diversity in Kemp’s ridley.