Genetic characterization of the marine turtle populations Chelonia mydas and Caretta caretta from the islands of Cabo Verde and São Tomé e Príncipe (Atlantic Ocean, Western Africa)
Arango, A.O. (2010). Genetic characterization of the marine turtle populations Chelonia mydas and Caretta caretta from the islands of Cabo Verde and São Tomé e Príncipe (Atlantic Ocean, Western Africa). MSc Thesis. Erasmus Mundus Master of Science in Marine Biodiversity and Conservation (EMBC)/Universidade do Algarve: Algarve. 24 pp.
Sea turtles are a natural legacy of Cabo Verde, Sao Tomé e Principe; two country Islands located in the Atlantic Ocean of Western Africa, where there is a well established tradition to exploit the animals. The unsustainable harvesting of this flagship species around the world and other threats like pollution or damage of nesting beaches have depleted their populations and they are now classified as endangered. The present study analyzes the genetic diversity of the Chelonia mydas and Caretta caretta marine turtle populations of Cabo Verde and Sao Tomé e Principe, with the objective of establishing their genetic variation and population structure, and thus contribute to future conservation and management plans. We wanted to evaluate if the loggerhead and green turtles of these islands show genetic differences (significant divergence) between nesting populations, within and among the diverse species. The work entailed extraction of genomic DNA, validation of a suite of microsatellite markers and genotyping of samples. The DNA extraction was successful for the total of 91 blood samples corresponding to different individuals. Each of the nDNA samples (n=91) were analyzed with five set of primers (Cm58, Cm72, Cc117, CcP7DO4 and CcP2F11) reported in the literature, which amplify microsatellites in different species. From a total 455 PCR reactions (5 primers x 91 samples) 360 were successfully amplified (79.12%). In General, all the primers did effectively amplified and crossed amplified the different DNA samples of C. mydas and C. caretta. for C. mydas the more informative locus was Cm72, while for C. caretta was CcP2F11. Despite deviation of HWE resulting along some turtle samples, the analysis of variances of the allele size frequencies and genetic distances conducted gave evidence to think that the populations of C. mydas and C. caretta analyzed here show genetic differences (significant divergence) between each other. This was confirmed by most of the locus used. The same analyses show no genetic difference or no significant divergence within species at the different sites of their occurrence. This means that the individuals of the species C. mydas found and sampled in the Islands of Sao Tomé, Principe (Praia Grande) and Principe (no specific sites) are part of the same population; and that the individuals of the species C. caretta found and sampled in the Island of Cabo Verde (Santiago Island) and Cabo Verde (not specific site) are also part of a same population. In this sense, the green turtles that feed and reproduce along Sao Tomé and Principe islands, are part of a same conservation unit, represented in connectivity between feeding and nesting habitats. For the species C. caretta at the archipelago of Cabo Verde would occur something similar, been the nesting females recorded and sampled in the site Cabo Verde (Santiago Island) the same breeding population related to the individuals sampled and registered along no specific sites of the Archipelago, although for the last ones there was no data recorded about the life state of the individuals. In terms of conservation, the findings explained above could contribute to design programs of management units at the study area, which ensure the gene flow given between sites of occurrence of the species, and at the same time, help to reduce anthropogenic impacts over them. With this, it is indispensable that interconnections among functional habitats and traits like life stages are respected, protected and maintained within the populations of turtles studied, and hopefully for other ones to come.
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