Sex ratios and natal origins of green turtles from feeding grounds in the Southwest Atlantic Ocean

Potential effects of climate change on living species are a widely debated topic. Species with temperature-dependent sex determination can be particularly impacted by warmer temperatures because unbalanced sex ratios could threaten population viability. In sea turtles, sex ratio estimates have highlighted the potential feminization of current populations, which tends to increase since warmer temperatures would generate more females. Here, we evaluated temporal variation in sex ratios of green turtles from feeding grounds of the Southwest Atlantic Ocean (SWA) using data from a 7-year time frame, from 2010 to 2016. We also evaluated natal origins of female and male green turtles from SWA based on mitochondria] DNA. Sex ratios of juvenile and adult green turtles were generally female-skewed across collection years. We identified 11 haplotypes in northeast SWA, and the haplotype composition of females and males was slightly different. Likewise, the estimated the natal origins of females and males were divergent. Ascension Island was estimated to be the main source of females while Guinea Bissau was estimated to be the main source of males. Studies evaluating natal origins of females and males independently are rare, this study provides one of the first assessments of the kind for green turtles in the SWA.

Automated summary

The potential effects of climate change on living species, particularly those with temperature-dependent sex determination, are widely debated. This study evaluated the temporal variation in sex ratios of green turtles in the Southwest Atlantic Ocean and found a female-skewed population trend. Additionally, the study identified different natal origins for female and male green turtles in the region, with Ascension Island being the main source of females and Guinea Bissau being the main source of males.