Armstrong Katrina C, Lippert Marilla, Hanson Erik, Nestor Victor, Cornwell Brendan, Walker Nia S, Golbuu Yimnang, Palumbi Stephen R
Department of Biology Hopkins Marine Station of Stanford University Pacific Grove California USA.
Palau International Coral Reef Center Koror Palau.
Ecol Evol. 2024 Dec 16;14(12):e70650. doi: 10.1002/ece3.70650. eCollection 2024 Dec.
Symbiont genotype plays a vital role in the ability of a coral host to tolerate rising ocean temperatures, with some members of the family Symbiodiniaceae possessing more thermal tolerance than others. While existing studies on genetic structure in symbiont populations have focused on broader scales of 10-100 s of km, there is a noticeable gap in understanding the seascape genetics of coral symbionts at finer-yet ecologically and evolutionarily relevant-scales. Here, we mapped short reads from 271 holobiont genome libraries of individual colonies to protein coding genes from the chloroplast genome to identify patterns of symbiont population genetic structure. Utilizing this low-pass method, we assayed over 13,000 bases from every individual, enabling us to discern genetic variation at a finer geographic scale than previously reported at the population level. We identified five common chloroplast SNP profiles present across Palau, with symbiont structure varying between Northern, mid-lagoon, and Southern regions, and inshore-offshore gradients. Although symbiont populations within reefs typically contained significant genetic diversity, we also observed genetic structure between some nearby reefs. To explore whether coral hosts retain their symbionts post-transplantation, we experimentally moved 79 corals from their native reefs to transplant sites with both different and similar chloroplast SNP profiles. Over 12 months, we observed 12 instances where transplanted corals changed profiles, often transitioning to a profile present in adjacent corals. Symbiont genetic structure between reefs suggests either low dispersal of symbionts or environmental selection against dispersers, both resulting in the potential for significant adaptive differentiation across reef environments. The extent to which local corals and their symbionts are co-adapted to environments on a reef-by-reef scale is currently poorly known. Chloroplast sequences offer an additional tool for monitoring symbiont genetics and coral-symbiont interactions when assisted migration is used in restoration.
共生体基因型在珊瑚宿主耐受海洋温度上升的能力中起着至关重要的作用，共生藻科的一些成员比其他成员具有更强的耐热性。虽然现有的关于共生体种群遗传结构的研究集中在10 - 100千米的更大尺度上，但在理解珊瑚共生体在更精细但与生态和进化相关的尺度上的海洋景观遗传学方面存在明显差距。在这里，我们将来自单个珊瑚群落的271个全生物基因组文库的短读长映射到叶绿体基因组的蛋白质编码基因上，以识别共生体种群遗传结构模式。利用这种低通量方法，我们对每个个体的13000多个碱基进行了检测，使我们能够在比之前在种群水平上报道的更精细的地理尺度上辨别遗传变异。我们在帕劳各地确定了五种常见的叶绿体单核苷酸多态性图谱，共生体结构在北部、泻湖中部和南部地区以及近岸 - 离岸梯度之间有所不同。尽管珊瑚礁内的共生体种群通常包含显著的遗传多样性，但我们也观察到一些附近珊瑚礁之间的遗传结构。为了探究珊瑚宿主在移植后是否保留其共生体，我们通过实验将79只珊瑚从它们的原生珊瑚礁转移到具有不同和相似叶绿体单核苷酸多态性图谱的移植地点。在12个月的时间里，我们观察到12例移植珊瑚改变图谱的情况，通常转变为相邻珊瑚中存在的图谱。珊瑚礁之间的共生体遗传结构表明共生体的扩散率较低，或者环境对扩散者进行选择，这两者都导致了在不同珊瑚礁环境中显著适应性分化的可能性。目前，当地珊瑚及其共生体在逐个珊瑚礁尺度上与环境共同适应的程度尚不清楚。当在恢复过程中使用辅助迁移时，叶绿体序列为监测共生体遗传学和珊瑚 - 共生体相互作用提供了额外的工具。
