Data from: Biodiversity dynamics and environmental occupancy of fossil azooxanthellate and zooxanthellate scleractinian corals

Scleractinian corals have two fundamentally different life strategies, which can be inferred from morphological criteria in fossil material. In the non-photosymbiotic group nutrition comes exclusively from heterotrophic feeding, whereas the photosymbiotic group achieves a good part of its nutrition from algae hosted in the coral’s tissue. These ecologic differences arose early in the evolutionary history of corals but with repeated evolutionary losses and presumably also gains of symbiosis since then. We assessed the biodiversity dynamics and environmental occupancy of both ecologic groups to identify times when the evolutionary losses of symbiosis as inferred from molecular analyses might have occurred and if these can be linked to environmental change. Two episodes are likely: The first was in the mid-Cretaceous when non-symbiotic corals experienced an origination pulse and started to become more common in deeper, non-reef habitats and on siliciclastic substrates initiating a long-term offshore trend in occupancy. The second was around the Cretaceous/Paleogene boundary with another origination pulse and increased occupancy of deep-water settings in the non-symbiotic group. Environmental factors such as rapid global warming associated with mid-Cretaceous anoxic events and increased nutrient concentrations in Late Cretaceous–Cenozoic deeper waters are plausible mechanisms for the shift. Turnover rates and durations are not significantly different between the two ecologic groups when compared over the entire history of scleractinians. However, the deep-water shift of non-symbiotic corals was accompanied by reduced extinction rates, supporting the view that environmental occupancy is a prominent driver of evolutionary rates.石珊瑚目（Scleractinian corals）存在两种截然不同的生存策略，该差异可通过化石材料的形态学标准加以推断。非光合共生类群的营养完全来源于异养摄食，而光合共生类群的大部分营养则取自寄居在珊瑚组织内的藻类。这些生态差异早在珊瑚演化史早期便已出现，但自那以后共生关系经历了多次演化丢失与大概率的重新获得。我们针对这两类生态类群的生物多样性动态与环境占据情况展开评估，旨在通过分子分析推断共生关系演化丢失的发生时段，并探究其是否与环境变化存在关联。存在两个可能的时段：其一为白垩纪中期，此时非共生珊瑚出现起源脉冲，并开始在更深的非礁生境以及硅质碎屑基质中愈发常见，开启了长期的离岸生境占据趋势；其二则大致位于白垩纪/古近纪界线附近，非共生类群再次出现起源脉冲，且深水生境的占据比例有所提升。诸如白垩纪中期缺氧事件伴生的快速全球变暖，以及晚白垩世-新生代深水水域营养浓度升高这类环境因素，或为该转变的合理驱动机制。若以石珊瑚的整个演化史为跨度进行比较，两类生态类群的周转速率与持续时长并无显著差异。不过，非共生珊瑚的深水生境转移伴随着灭绝速率的降低，这一结果支撑了“环境占据是演化速率的重要驱动因素”这一观点。