GEOMAR Helmholtz Centre for Ocean Research Kiel, Research Unit Experimental Ecology - Benthic Ecology, Wischhofstraße 1-3, 24148, Kiel, Germany.
Department of Biology, University of Konstanz, Universitätsstraße 10, Konstanz, 78464, Germany.
BMC Ecol Evol. 2023 Aug 26;23(1):42. doi: 10.1186/s12862-023-02153-7.
The widespread Indo-Pacific coral species Pocillopora acuta Lamarck, 1816 displays varying levels of asexual versus sexual reproduction, with strong repercussions on genetic diversity, connectivity and genetic structuring within and among populations. For many geographic regions, baseline information on genetic diversity is still lacking, particularly in the Andaman Sea. The region suffered a massive heat-induced bleaching event in 2010 with high coral cover loss of branching coral species such as P. acuta. A subsequent bleaching in 2016, however, revealed a mild bleaching response in pocilloporids compared to other coral taxa in the region, suggesting that rare, heat tolerant genotypes had been selected by the 2010 bleaching event. In order to test whether this potential 'evolutionary rescue' event has led to a low genetic diversity, we conducted a population genetic survey covering a total of nine different P. acuta populations (336 individuals) along a 50 km coastal stretch around Phuket Island, Thailand. We used six microsatellite markers to assess genotypic diversity and to determine the prevalent mode of reproduction (i.e. sexual or asexual recruitment).
In contrast to other Indian Ocean P. acuta populations, the majority of corals in this study adopted a sexual reproduction mode (75% across all populations). At the same time, substantial regional gene flow was observed around Phuket Island with strong genetic differentiation as indicated by three genetic clusters that were separated by only a few kilometers. Patterns of isolation by distance over 0.7 - 40 km suggest small-scale genetic barriers, such as changing currents throughout each monsoonal season, potentially contributing to locally restricted dispersal of P. acuta larvae.
The occurrence of distinct genetic clusters within short coastal stretches suggests that the 2010 bleaching event has not led to extreme genetic impoverishment. While more in-depth genomic analyses are necessary to investigate changes in genetic diversity following extreme bleaching events, our results will help guide conservation efforts to maintain genetic diversity of a coral species that likely will be dominant in future, warmer Andaman Sea reefs.
广泛分布的印度洋-太平洋珊瑚物种尖叶珊瑚（Pocillopora acuta Lamarck, 1816）表现出不同程度的无性与有性繁殖，这对遗传多样性、种群内和种群间的连通性和遗传结构具有强烈影响。对于许多地理区域，遗传多样性的基线信息仍然缺乏，特别是在安达曼海。该地区在 2010 年经历了一场大规模的热诱导白化事件，分枝珊瑚物种（如尖叶珊瑚）的珊瑚覆盖率大量损失。然而，2016 年的一次随后的白化事件显示，与该地区的其他珊瑚类群相比，尖叶珊瑚属珊瑚表现出轻度白化反应，这表明在 2010 年的白化事件中，已经选择了罕见的耐热基因型。为了测试这种潜在的“进化拯救”事件是否导致遗传多样性降低，我们对泰国普吉岛周围 50 公里长的沿海地带的总共 9 个不同的尖叶珊瑚种群（336 个个体）进行了种群遗传调查。我们使用了 6 个微卫星标记来评估基因型多样性，并确定主要的繁殖模式（即有性或无性繁殖）。
与其他印度洋尖叶珊瑚种群相比，本研究中的大多数珊瑚采用了有性繁殖模式（所有种群中占 75%）。与此同时，在普吉岛周围观察到大量的区域基因流动，存在强烈的遗传分化，表明有三个遗传群落在相隔仅几公里的地方分离。0.7-40 公里范围内的隔离距离模式表明，小尺度的遗传障碍，如每个季风季节不断变化的海流，可能会限制尖叶珊瑚幼虫的局部扩散。
在短的沿海地带发现明显的遗传群集表明，2010 年的白化事件并没有导致遗传严重枯竭。虽然需要更深入的基因组分析来调查极端白化事件后遗传多样性的变化，但我们的研究结果将有助于指导保护努力，以维持在未来温暖的安达曼海珊瑚礁中可能占主导地位的珊瑚物种的遗传多样性。
