Investigating the reproductive behaviour of the green sea turtle (Chelonia mydas) using parentage analysis

Abstract

The reproductive systems of natural populations can greatly impact their genetic diversity by preventing or encouraging inbreeding. It is therefore crucial to have a comprehensive understanding of the mating system to evaluate a population’s ability to maintain genetic diversity over time. In this study, we examine the mating system of an endangered population of green sea turtles in Tetiaroa, French Polynesia. We determine if different mating behaviours serve as strategies to avoid inbreeding. We genotyped 107 nesting females and 1483 hatchlings from 549 nests and used 23 microsatellite markers to reconstruct the genotypes of the fathers. We assessed the level of inbreeding and relatedness of the parent pairs and explored the correlation between relatedness and fitness parameters in the offspring. We determined the mating behaviours of both males and females and investigated if specific behaviours were linked to different levels of relatedness. Our results showed that 27 fathers and 31 mothers were responsible for the genotypes of 445 hatchlings from 105 nests. Global Fis was significant, and levels of relatedness were higher than expected through random mating, indicating inbreeding and non-random partner selection. However, we did not find any mating behaviours that were associated with lower relatedness levels than the general population, suggesting that they are not part of an inbreeding avoidance strategy. Ultimately, this study illuminates the reproductive system of green turtles and shows that this population is susceptible to inbreeding. Additionally, our research demonstrates the effectiveness of parentage analysis in understanding the reproductive behaviour of elusive species.