Genetic assessment of population structure and connectivity in the threatened Mediterranean coral Astroides calycularis (Scleractinia, Dendrophylliidae) at different spatial scales

Understanding dispersal patterns, population structure and connectivity among populations is helpful in the management and conservation of threatened species. Molecular markers are useful tools as indirect estimators of these characteristics. In this study we assess the population genetic structure of the endemic Mediterranean coral Astroides calycularis in the Alboran Sea at local and regional scales, and at three localities outside of this basin. Bayesian clustering methods, traditional F-statistics and Dest statistics were used to determine the patterns of genetic structure. Likelihood and coalescence approaches were used to infer migration patterns and effective population sizes. The results obtained reveal a high level of connectivity among localities separated by as much as one kilometer and moderate levels of genetic differentiation among more distant localities, somewhat corresponding with a stepping-stone model of gene flow and connectivity. These data suggest that connectivity among populations of this coral is mainly driven by the biology of the species, with low dispersal abilities; in addition, hydrodynamic processes, oceanographic fronts and the distribution of rocky substrate along the coastline may influence larval dispersal.

解析种群扩散模式、种群结构与种群连通性，对于受威胁物种的管理与保护具有重要意义。分子标记（Molecular markers）是用于间接估算上述特征的有效工具。本研究针对阿尔沃兰海及该海域外3个采样点的地中海特有珊瑚Astroides calycularis，分别从局域与区域两个尺度开展种群遗传结构分析。研究采用贝叶斯聚类法（Bayesian clustering methods）、传统F统计量（F-statistics）及Dest统计量（Dest statistics）解析种群遗传结构模式；同时借助似然法（Likelihood）与溯祖分析法（coalescence approaches）推断种群迁移模式与有效种群大小。研究结果显示，间隔可达1公里的采样点间仍维持较高连通性，而较远采样点间则呈现中等程度的遗传分化，该格局与基因流及连通性的踏脚石模型（stepping-stone model）较为吻合。上述数据表明，该珊瑚种群的连通性主要受物种自身生物学特性驱动，其扩散能力较弱；此外，水动力过程、海洋锋面及沿岸岩质基质的分布格局，或可对幼体扩散产生影响。