Data from: Asynchronous spawning in sympatric populations of a hard coral reveals cryptic species and ancient genetic lineages

Genetic subdivision within a species is a vital component of the evolution of biodiversity. In some species of Acropora corals in Western Australia, con-specific individuals spawn in two seasons six months apart, which has the potential to impede gene flow and result in genetic divergence. Genetic comparison of sympatric spring and autumn spawners of Acropora samoensis was conducted to assess the level of reproductive isolation and genetic divergence between the spawning groups based on multiple loci (13 microsatellite loci, the mitochondrial control region and two nuclear introns). Bayesian clustering and principal co-ordinates analysis of the microsatellite loci showed a high level of genetic differentiation between the spawning groups (F’ST = 0.30; P < 0.001), as did the sequence data from PaxC and Calmodulin (ΦST = 0.97 and 0.31, respectively). At the PaxC locus the autumn- and spring-spawners were associated with two ancient lineages that were separated by an evolutionary distance of 12.7%, over twenty times the level of divergence at the Calmodulin locus (0.5%). Statistical tests indicate divergent selection in PaxC, suggesting this gene may play a role in coral spawning. This study indicates that the autumn- and spring-spawners represent two cryptic species, and highlights the importance of asynchronous spawning as a mechanism influencing speciation in corals.

物种内的遗传亚结构是生物多样性演化的核心组成部分。在西澳大利亚的部分鹿角珊瑚属（Acropora）珊瑚中，同种个体可在间隔六个月的两个季节产卵，这一现象可能阻碍基因交流并引发遗传分化。本研究以同域分布的萨摩亚鹿角珊瑚（Acropora samoensis）春、秋产卵群体为对象开展遗传比较分析，基于多个分子标记位点（13个微卫星位点（microsatellite loci）、线粒体控制区（mitochondrial control region）以及2个核内含子（nuclear introns）），评估产卵群体间的生殖隔离水平与遗传分化程度。对微卫星位点的贝叶斯聚类（Bayesian clustering）与主坐标分析（principal co-ordinates analysis）结果显示，产卵群体间存在高度遗传分化（F’ST = 0.30; P < 0.001）；PaxC与钙调蛋白（Calmodulin）的序列数据分析也得到了一致结果（ΦST分别为0.97和0.31）。在PaxC基因位点上，秋、春产卵群体分属两个古老谱系，二者的进化距离达12.7%，是钙调蛋白位点分化水平（0.5%）的二十余倍。统计检验结果表明PaxC基因受到歧化选择（divergent selection），提示该基因可能在珊瑚产卵过程中发挥作用。本研究证实，春、秋产卵群体实为两个隐存种（cryptic species），并凸显了异步产卵作为影响珊瑚物种形成的关键机制的重要性。