关键词: 澄黄滨珊瑚, 遗传连通性, 微卫星标记, 径流, 岸礁结构, 海流

Abstract: Porites lutea, the representative species of reef building corals around Hainan Island, is a spawning, massive coral with strong environmental adaptability. Exploring the genetic structure and connectivity of this species will help to reveal the genetic diversity pattern and larval migration path of coral metapopulation around Hainan Island, thus clarifying the recovery potential of coral reefs. In this study, 11 P. lutea microsatellite markers were screened to analyze the genetic structure of 10 populations of Hainan fringing reefs and 1 population (XsR) in Xisha Islands. The results showed that, overall the genetic diversity of all populations was medium to low, with the average allelic richness Rs ranged from 2.8 ± 1.3 (Basuo population, Bs) to 3.7 ± 1.7 (Linchang Reef population, LcR), and the average observed and expected heterozygosity ranged from 0.31 (Tongguling population, Tgl) to 0.54 (Dachan Reef population, DcR) and 0.50 (Leigong Island population, LgI) to 0.64 (Haiwei population, Hw), respectively. Except for Longwan Reef population (LwR) and Dazhou Island population (DzI), which located in the east of Hainan Island, and Basuo population (Bs) and Dachan Reef population (DcR (in the west of Hainan Island), all other populations (7/11) showed evidence of heterozygote deficiency. According to genetic differentiation, Hainan Island populations were divided into two groups: the north-south-east genetically connected zone and the west coast, and the differentiation between the two branches (AMOVA, 0.092) was significant. The former group included Bs, Luhuitou population (Lht), DzI, LgI and Mulantou population (Mlt), due to the significant gene flow created by exchange of ocean currents, there was no obvious genetic differentiation among these five coastal populations, whereas the gene flow of the offshore populations (LcR, DcR and Hw) of the west coast was blocked due to the discontinuity of coastal reefs and slow coastal currents. LwR in the east coast also converges to the west branch, which may be due to the isolation by environment and the convergent adaptation to offshore environment. Although the distance between Hw and Bs is less than 50 km, but they are obviously differentiated, possibly due to the isolation by salinity fluctuation and suspended sediments caused by the runoff of Changhua River. Tgl showed strong inbreeding, low heterozygosity and non-random mating characteristics because it was located in the wave shadow area of Tongguling headland, and the runoff of Bamen River restricted its gene exchange with other coastal reef populations. Represented by P. lutea metapopulations, the fringing reefs of Hainan Island has the natural resilience responding to environmental stress due to the strong gene flow and the genetic differentiation caused by ocean current, runoff and complex fringing reef structure, as well as the environmental differences between nearshore and offshore. The genetic differentiation between Xisha Islands population and the coastal reef populations of Hainan Island was large, showing significant geographical isolation. Qilianyu Island may have lost the ability to replenish Hainan Island with coral larvae because the coral reefs there have declined.

Key words: Porites lutea, Genetic connectivity, Microsatellite marker, Runoff, Fringing reef structures, Currents