Coral cover on tropical reefs has declined during the last three decades due to the combined effects of climate change, destructive fishing, pollution, and land use change. Drastic reductions in greenhouse gas emissions combined with effective coastal management and conservation strategies are essential to slow this decline. Innovative approaches, such as selective breeding for adaptive traits combined with large-scale sexual propagation, are being developed with the aim of pre-adapting reefs to increased ocean warming. However, there are still major gaps in our understanding of the technical and methodological constraints to producing corals for such restoration interventions. Here we propose a framework for selectively breeding corals and rearing them from eggs to 2.5-year old colonies using the coral Acropora digitifera as a model species. We present methods for choosing colonies for selective crossing, enhancing early survivorship in ex situ and in situ nurseries, and outplanting and monitoring colonies on natal reefs. We used a short-term (7-day) temperature stress assay to select parental colonies based on heat tolerance of excised branches. From six parental colonies, we produced 12 distinct crosses, and compared survivorship and growth of colonies transferred to in situ nurseries or outplanted to the reef at different ages. We demonstrate that selectively breeding and rearing coral colonies is technically feasible at small scales and could be upscaled as part of restorative assisted evolution initiatives. Nonetheless, there are still challenges to overcome before selective breeding can be implemented as a viable conservation tool, especially at the post-settlement and outplanting phases. Although interdisciplinary approaches will be needed to overcome many of the challenges identified in this study, selective breeding has the potential to be a viable tool within reef managers’ toolbox to support the persistence of selected reefs in the face of climate change.

中文翻译：

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选择性繁殖珊瑚以辅助进化的框架

在过去的三十年中，由于气候变化，破坏性捕鱼，污染和土地利用变化的综合影响，热带珊瑚礁的珊瑚覆盖率有所下降。大幅减少温室气体排放与有效的沿海管理和保护策略相结合，对于减缓这种下降势在必行。正在开发创新方法，例如针对适应性状的选择性育种和大规模的性繁殖，目的是预先适应礁石以增加海洋变暖。但是，在我们对为这种恢复干预措施生产珊瑚的技术和方法学限制的理解上，仍然存在重大差距。在这里，我们提出了一个框架，以珊瑚为例，将选择性地繁殖珊瑚并将其从卵中繁殖到2.5岁的殖民地。我们介绍了选择菌落进行选择性杂交，增强非原生境和就地苗圃的早期生存率以及在原生礁上移栽和监测菌落的方法。我们使用了短期（7天）的温度胁迫测定法，基于切除的树枝的耐热性选择亲本菌落。从六个亲本菌落中，我们产生了12个不同的杂交，并比较了在不同年龄转移到原地苗圃或外植到礁石上的菌落的存活率和生长情况。我们证明选择性繁殖和饲养珊瑚群落在小规模上在技术上是可行的，并且可以作为恢复性辅助进化计划的一部分而扩大规模。尽管如此，在选择育种作为可行的保护工具之前，仍然有许多挑战需要克服，特别是在结算后和移栽阶段。尽管将需要跨学科的方法来克服本研究中确定的许多挑战，但是选择性育种有可能成为珊瑚礁管理者工具箱中的一种可行工具，以支持面对气候变化的选定珊瑚礁的持久性。