Biodiversity dynamics and environmental occupancy of fossil azooxanthellate and zooxanthellate scleractinian corals
Biodiversity dynamics and environmental occupancy of fossil azooxanthellate and zooxanthellate scleractinian corals
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DOI：
10.1017/pab.2015.6
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发表时间：
2015-06-01
期刊：
影响因子：
2.7
通讯作者：
Kocsis, Adam T.
中科院分区：
文献类型：
--
作者：
Kiessling, Wolfgang;Kocsis, Adam T.
硬核珊瑚有两种根本不同的生活策略，这可以从化石材料的形态标准推断出来。在非光共生组中，营养完全来自异养喂养，而光共生组则从珊瑚组织中的藻类中获得很大一部分营养。这些生态差异出现在珊瑚进化史的早期，但从那时起，随着不断的进化损失，可能也获得了共生关系。我们评估了这两个生态群体的生物多样性动态和环境占用，以确定从分子分析推断的共生进化损失可能发生的时间，以及这些是否与环境变化有关。可能有两个时期：第一次是在白垩纪中期，非共生珊瑚经历了一个起源脉冲，开始在更深的非珊瑚礁栖息地和硅塑性基质上变得越来越普遍，开始了长期的近海占用趋势。第二次是在白垩纪/古近纪边界附近，另一个起源脉冲，在非共生群中增加了深水环境的占用。环境因素，如与中白垩纪缺氧事件相关的快速全球变暖，以及晚白垩纪-新生代深水中营养物质浓度的增加，是这种转变的合理机制。当比较整个硬核动物的历史时，两个生态群之间的周转率和持续时间没有显着差异。然而，非共生珊瑚的深水迁移伴随着灭绝率的降低，这支持了环境占用是进化速度的重要驱动因素的观点。
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.