Levitan Don R, Olsen Kevin C, Best Rachael M, Edmunds Peter J
Department of Biological Science, Florida State University, Tallahassee, Florida, USA.
State Fisheries Genomics Lab, Coastal Oregon Marine Experiment Station, Department of Fisheries, Wildlife and Conservation Sciences, Hatfield Marine Science Center, Oregon State University, Newport, Oregon, USA.
Ecology. 2025 May;106(5):e70102. doi: 10.1002/ecy.70102.
The abundance of many Caribbean corals has declined over the past few decades, yet now Porites astreoides is more common on many shallow reefs than in the 1980s and shows evidence of local adaptation. We compare the small-scale (1-8000 m) genetic structure of this brooding species and the broadcasting coral Orbicella annularis on reefs (<14 m depth) in St. John, US Virgin Islands, to examine how larval dispersal and asexual propagation contribute to the retention of genotypes within reefs. Populations of P. astreoides have genetic structure across reefs separated by a few 100 m, increased relatedness within reefs, and parthenogenetic larval propagation confirmed by parent-offspring genotyping. Within reefs, P. astreoides colonies <1 m apart are more related, independent of clonal reproduction, than corals at greater distances. In contrast, O. annularis lacks across-reef genetic structure, has low relatedness within and among reefs, and does not produce asexual larvae. Small-scale genetic structure and high relatedness in P. astreoides are evident even without considering asexual propagation, but asexual reproduction enhances these differences. Neither species shows the genetic signature of inbreeding or reduced genotypic diversity despite the high within-site relatedness of P. astreoides. Monitoring on these reefs from 1987 indicates that Porites has increased in abundance while Orbicella has decreased in abundance. The success of Porites is due to greatly increased settlement and recruitment compared with Orbicella. Together these results indicate that high numbers of locally retained and successful genotypes might explain the relative success of Porites on shallow, present-day reefs in the Caribbean.
在过去几十年里，许多加勒比珊瑚的数量有所下降，但如今，星孔珊瑚（Porites astreoides）在许多浅礁上比20世纪80年代更为常见，并且显示出局部适应的迹象。我们比较了这种卵胎生珊瑚物种与散播型珊瑚环纹菊珊瑚（Orbicella annularis）在美属维尔京群岛圣约翰岛深度小于14米的珊瑚礁上的小尺度（1 - 8000米）遗传结构，以研究幼体扩散和无性繁殖如何有助于基因型在珊瑚礁内的留存。星孔珊瑚种群在相隔几百米的珊瑚礁间具有遗传结构，珊瑚礁内的亲缘关系增加，并且通过亲子基因分型证实了孤雌生殖幼体繁殖。在珊瑚礁内，相距小于1米的星孔珊瑚群体比相距更远的珊瑚具有更高的亲缘关系，这与克隆繁殖无关。相比之下，环纹菊珊瑚缺乏跨礁遗传结构，礁内和礁间的亲缘关系较低，并且不产生无性幼体。即使不考虑无性繁殖，星孔珊瑚的小尺度遗传结构和高亲缘关系也很明显，但无性繁殖加剧了这些差异。尽管星孔珊瑚在局部具有高亲缘关系，但两个物种均未显示出近亲繁殖的遗传特征或基因型多样性降低。自1987年以来对这些珊瑚礁的监测表明，星孔珊瑚数量增加而环纹菊珊瑚数量减少。星孔珊瑚的成功归因于与环纹菊珊瑚相比，其定居和补充数量大幅增加。这些结果共同表明，大量局部留存且成功的基因型可能解释了星孔珊瑚在当今加勒比浅礁上相对成功的原因。
