In many plant and sessile marine invertebrate (SMI) taxa, population and community dynamics are heavily influenced by processes occurring during the dispersal and establishment phases. The Janzen–Connell (J–C) hypothesis predicts increased survival of early life stages with decreasing conspecific density and increased distance from conspecific adults. Evidence of J–C effects in maintaining diversity is common in plant communities, but its importance in SMI communities remains unclear. Under controlled aquarium conditions, we examined the effect of density-dependence and adult conspecific water treatments (absent/present) on propagule settlement success and settler post-settlement survival, along with associated spatial patterns, for six broadcast-spawning, reef-building coral species from three families. We also tested if settlement success was linked to increasing propagule species diversity for three coral species from two families. We found that the probability of settlement was density independent and not influenced by adult present water treatments. Yet, adult present water treatments and settler density did have a synergistic negative effect on the probability of short-term settler survival for all species examined. Settlers also showed greater spatial aggregation as their numbers increased, but were less aggregated in adult present water treatments compared to those in adult absent water treatments. We further show evidence of significant species interactions among propagules, as settlement in single-species trials was four-fold higher compared to mixed-species trials. Our findings from controlled experimental arenas indicate that the early establishment of corals was predominantly limited by density-dependent settler–adult interactions among conspecifics and propagule–propagule interactions among heterospecifics. Thus, the proximity to established conspecific adults, settler density and species diversity of propagules are relevant drivers of local coral community diversity and structure. Based on these outcomes, we suggest that the J–C hypothesis, with demonstrated importance for plants, is partially upheld for reef corals.

中文翻译：

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Janzen-Connell 效应在造礁珊瑚中得到部分支持：成体的存在与定居者密度相互作用以限制建立

在许多植物和无柄海洋无脊椎动物 (SMI) 分类群中，种群和群落动态受到扩散和建立阶段发生的过程的严重影响。Janzen-Connell (J-C) 假设预测生命早期阶段的存活率随着同种密度的降低和与同种成虫的距离增加而增加。J-C 效应维持多样性的证据在植物群落中很常见，但其在 SMI 群落中的重要性仍不清楚。在受控的水族箱条件下，我们研究了密度依赖性和成体同种水处理（不存在/存在）对六种广播产卵、造礁珊瑚的繁殖体定居成功和定居者定居后生存的影响，以及相关的空间模式来自三个科的物种。我们还测试了定居成功是否与增加来自两个科的三种珊瑚物种的繁殖物种多样性有关。我们发现沉降的概率与密度无关，不受成人现有水处理的影响。然而，成人目前的水处理和定居者密度确实对所有被检查物种的短期定居者生存概率产生了协同的负面影响。随着数量的增加，定居者也表现出更大的空间聚集，但与成人缺水处理相比，在成人存在的水处理中聚集较少。我们进一步展示了繁殖体之间显着物种相互作用的证据，因为与混合物种试验相比，单一物种试验中的沉降高四倍。我们在受控实验领域的研究结果表明，珊瑚的早期建立主要受到同种之间依赖密度的定居者 - 成虫相互作用和异种之间繁殖体 - 繁殖体相互作用的限制。因此，接近已建立的同种成虫、定居者密度和繁殖体的物种多样性是当地珊瑚群落多样性和结构的相关驱动因素。基于这些结果，我们建议 J-C 假设对植物具有重要意义，对珊瑚礁部分支持。繁殖体的定居者密度和物种多样性是当地珊瑚群落多样性和结构的相关驱动因素。基于这些结果，我们建议 J-C 假设对植物具有重要意义，对珊瑚礁部分支持。繁殖体的定居者密度和物种多样性是当地珊瑚群落多样性和结构的相关驱动因素。基于这些结果，我们建议 J-C 假设对植物具有重要意义，对珊瑚礁部分支持。