Diversidade genética da tartaruga-verde (Chelonia mydas) na área de proteção ambiental Costa dos Corais

Abstract

The green turtle (Chelonia mydas) has a slow development and a cosmopolitan distribution, occurring in tropical and subtropical waters. This species performs several migrations at all stages of its ontogeny. the feeding groups (FG), where they spend most of their lives, are composed of individuals of different size classes and different natal origins, for this reason they are called mixed stocks. Female turtles demonstrate a philopatric behavior, which would be the tendency to return to the natal beach to nest during their next reproductive cycles. This behavior produces a genetic structure between nesting sites (NS), which can usually be detected in mitochondrial DNA, as it presents maternal inheritance. In this study, genetic analyzes were carried out to assess whether the natal origin of green turtles varies according to the size class of individuals that use the Área de Proteção Ambiental Costa dos Corais (APACC) as FG. Muscle tissue samples were collected from 115 specimens of Chelonia mydas, which were separated into two size classes: juveniles recently recruited to FG (CCL ≤45 cm; N=53) and established juveniles to FG (CCL ≥55 cm; N=63). Mitochondrial DNA sequences were generated and haplotypes were identified using the Archie Carr Center for Sea Turtle Research database. Haplotype (H) and nucleotide (π) diversities were estimated, and Molecular Variance Analysis (AMOVA) was performed to verify whether there is genetic differentiation between size classes. A mixed stock analysis was employed to assess the natal origins of individuals present in the study area. For this analysis, the many-to-one approach was used, where the probable natal origin of individuals in a mixed stock (feeding groups) is estimated, taking into account multiple sources (nesting sites). Eight haplotypes were found in the study area, and only CM-A8 (68%; 66%) and CM-A5 (25%; 18%) were the most frequent haplotypes for the two size classes, ≤45 cm and ≥ 55 cm respectively. AMOVA indicated that genetic variation was not significant between the two size classes (FST = 0.00393, p = 0.25762), and that the greatest genetic variation was within classes (99.61%). Mixed stock analyzes revealed Ascension Island (58.69%) and Guinea-Bissau (46.78%) as the main contributors to the composition of individuals in the APACC, ≤45 cm and ≥55 cm respectively. Trindade Island (32%) showed a significant contribution only for specimens ≥55 cm. The results of this study help to understand the genetic diversity of C. mydas in the FG for APACC, which was similar to other FGs in the Southwest Atlantic. It was possible to notice that the study area has connectivity with several NS of the Atlantic, thus highlighting the APACC as an important area of development and feeding of this species. Such results, together with additional research, may define key areas for green turtle foraging within the APACC that, with effective management, will form an axis to help protect the species in the region.