Abstract
The Qilianyu cluster of the Xisha (Paracel) Islands has one of the few remaining green turtle Chelonia mydas rookeries in the China region. Genetic samples were obtained from dead green turtle embryos and hatchlings salvaged from post-hatched nests at Middle Island (n = 3), North Island (n = 9) and South Sand (n = 1) of the Qilianyu cluster in 2017-2019. The ~800 bp mitochondrial DNA control region was sequenced from the samples, and 5 haplotypes were identified belonging to 2 documented clades (clades III and VIII), including 2 new haplotypes (CmP243.1 and CmP244.1) and 3 previously reported haplotypes (CmP18.1, CmP19.1, CmP20.1). These results were combined with previously published mtDNA data for the Qilianyu cluster and nearby (~93 km) Yongle Islands indicating a lack of differentiation based on truncated 384 bp control region sequences (exact test, p = 0.0997; FST = 0.015, p = 0.2760), to represent a single Xisha Islands rookery. The rookery at the Xisha Islands was significantly differentiated (p < 0.01) from all 19 management units (MUs) documented in the Indo-Pacific and Japan regions, supporting recognition of the Xisha Islands rookery as a new independent MU. The results will help inform national and international conservation action plans by China and the countries around the South China Sea to protect green turtles in the West Pacific Ocean.
Highlights
The green turtle Chelonia mydas (Linnaeus, 1758) has a global distribution in tropical and subtropical coastal waters, across at least 140 countries, of which more than 80 contain nesting grounds (Groombridge & Luxmoore 1989, Hirth 1997)
Pairwise tests for population structure were conducted using exact tests and FST analyses based on haplotype frequencies, and using ΦST that incorporated information on genetic distance
Phylogeographic relationships of all haplotypes documented in the Indo-Pacific and Japan regions (Ng et al 2014, 2017, Jensen et al 2019, Gaillard et al 2021) and this study were inferred by constructing a neighbor-joining (NJ) tree, including the flatback turtle Natator depressus as an outgroup, using MEGA 6.06 with 10 000 bootstrap pseudo-replications (Tamura et al 2013)
Summary
The green turtle Chelonia mydas (Linnaeus, 1758) has a global distribution in tropical and subtropical coastal waters, across at least 140 countries, of which more than 80 contain nesting grounds (Groombridge & Luxmoore 1989, Hirth 1997). Global green turtle population assessments have identified subpopulations in order to conduct status and risk assessment at the appropriate geographic scale useful for conserving genetic diversity (Seminoff 2004, Komoroske et al 2017). These regional subpopulations include regional management units (RMUs) (Wallace et al 2010) and distinct population segments (DPSs) (Seminoff et al 2015). Based on the 386 bp control region segments, 11 clades (clades I−XI) were identified from 127 rookeries of green turtles globally, and 58 MUs were proposed in 12 geographical regions considered to be evolutionarily distinct (Jensen et al 2019). Genetic samples were collected in 2017−2019 from post-hatched green turtle nests in the Qilianyu cluster in order to characterize the mtDNA diversity and to conduct comparative analyses with published data to determine population
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