Data from: Spatial and temporal genetic structure of Symbiodinium populations within a common reef-building coral on the central Great Barrier Reef

The dinoflagellate photosymbiont Symbiodinium plays a fundamental role in defining the physiological tolerances of coral holobionts, but little is known about the dynamics of these endosymbiotic populations on coral reefs. Sparse data indicate that Symbiodinium populations show limited spatial connectivity; however, no studies have investigated temporal dynamics for in hospite Symbiodinium populations following significant mortality and recruitment events in coral populations. We investigated the combined influences of spatial isolation and disturbance on the population dynamics of the generalist Symbiodinium type C2 (ITS1 rDNA) hosted by the scleractinian coral Acropora millepora in the central Great Barrier Reef. Using eight microsatellite markers, we genotyped Symbiodinium in a total of 401 coral colonies, which were sampled from seven sites across a 12-year period including during flood plume–induced coral bleaching. Genetic differentiation of Symbiodinium was greatest within sites, explaining 70–86% of the total genetic variation. An additional 9–27% of variation was explained by significant differentiation of populations among sites separated by 0.4–13 km, which is consistent with low levels of dispersal via water movement and historical disturbance regimes. Sampling year accounted for 6–7% of total genetic variation and was related to significant coral mortality following severe bleaching in 1998 and a cyclone in 2006. Only 3% of the total genetic variation was related to coral bleaching status, reflecting generally small (8%) reductions in allelic diversity within bleached corals. This reduction probably reflected a loss of genotypes in hospite during bleaching, although no site-wide changes in genetic diversity were observed. Combined, our results indicate the importance of disturbance regimes acting together with limited oceanographic transport to determine the genetic composition of Symbiodinium types within reefs.

共生腰鞭毛虫虫黄藻（Symbiodinium）是决定珊瑚共生体（coral holobionts）生理耐受特性的核心因子，但学界对珊瑚礁内这类内共生种群的动态变化尚知之甚少。现有零散数据显示，虫黄藻种群的空间连通性较为有限，但目前尚无研究探讨珊瑚种群发生大规模死亡与补充事件后，宿存于珊瑚体内的虫黄藻种群的时间动态变化。本研究以大堡礁（Great Barrier Reef）中部海域石珊瑚（scleractinian coral）宿主多孔鹿角珊瑚（Acropora millepora）所共生的泛适性虫黄藻C2型（ITS1 rDNA）为研究对象，探讨空间隔离与扰动因子对其种群动态的联合影响。本研究利用8个微卫星标记（microsatellite markers），对401个珊瑚群体的虫黄藻进行基因分型；样本采集自7个采样点，覆盖12年的时间跨度，其中包含洪水羽流诱发珊瑚白化事件的时期。虫黄藻的遗传分化在采样点内部最为显著，可解释总遗传变异的70%~86%。另有9%~27%的遗传变异可归因于相距0.4~13 km的采样点之间的种群显著分化，这与水流介导的低水平扩散以及历史扰动格局的特征相符。采样年份可解释总遗传变异的6%~7%，这与1998年严重白化事件及2006年飓风引发的大规模珊瑚死亡密切相关。仅有3%的总遗传变异与珊瑚白化状态相关，反映出白化珊瑚体内的等位基因多样性普遍小幅降低（降幅约8%）。尽管未观测到采样点整体的遗传多样性变化，但这种多样性降低可能源于白化过程中宿存于珊瑚体内的虫黄藻基因型发生了丢失。综合来看，本研究结果表明，扰动格局与有限的海洋环流输运共同作用，是决定礁体内虫黄藻类群遗传组成的关键因素。