Reductions in body size of benthic macroinvertebrates as a precursor of the early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal
Reductions in body size of benthic macroinvertebrates as a precursor of the early Toarcian (Early Jurassic) extinction event in the Lusitanian Basin, Portugal
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DOI：
10.1017/pab.2019.11
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发表时间：
2019-03
期刊：
影响因子：
2.7
通讯作者：
V. Piazza;L. V. Duarte;J. Renaudie;M. Aberhan
中科院分区：
文献类型：
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作者：
V. Piazza;L. V. Duarte;J. Renaudie;M. Aberhan
抽象的。机体缩小是生物体对环境胁迫的一种常见反应。研究早期Toarcian继承在葡萄牙的卢西塔尼亚盆地，我们测试是否壳大小的底栖海洋生物群落的双壳类和腕足类的变化在全球变暖相关的Toarcian海洋缺氧事件（T-OAE）之前。随着时间的推移，壳大小的统计分析表明，平均壳大小的社区显着下降之前的T-OAE。这种趋势在腕足类中是明显的，是由于随着时间的推移，较大的物种变得不那么丰富，而在双壳类中并不明显，这表明对环境压力的解耦反应。贝壳大小的减少先于与早期Toarcian灭绝事件相关的标准化样本水平物种丰富度的下降。海洋无脊椎动物的外壳尺寸在生物多样性变化开始之前就已缩小，这表明，更普遍的体型缩小可能是气候变化造成的物种随后丧失和群落一级更替的前兆。沉积学证据反对缺氧作为灭绝的驱动因素，以及在所研究的演替中腕足动物群的先前尺寸减小，尽管低氧水平被广泛认为是全球早期Toarcian灭绝率升高的原因。腕足动物的平均壳大小减少，但双壳类的停滞很难用海洋酸化来解释，因为实验工作表明，腕足动物可以适应pH值降低，尽管长期的代谢成本和潜在的进化适应尚不清楚。在卢西塔尼亚盆地早期Toarcian温度上升似乎是一个合理的因素，在两个多样性下降与T-OAE和前面的平均壳大小的减少，因为在现代双壳类的耐热性是最高的海洋无脊椎动物。
Abstract. Reduction of body size is a common response of organisms to environmental stress. Studying the early Toarcian succession in the Lusitanian Basin of Portugal, we tested whether the shell size of benthic marine communities of bivalves and brachiopods changed at and before the global, warming–related Toarcian oceanic anoxic event (T-OAE). Statistical analyses of shell size over time show that the mean shell size of communities decreased significantly before the T-OAE. This trend is distinct in brachiopods and is caused by larger-sized species becoming less abundant over time, whereas it is not significant in bivalves, suggesting a decoupled response to environmental stress. Reductions in shell size precede the decline in standardized sample-level species richness associated with the early Toarcian extinction event. Such decreases in the shell size of marine invertebrates, well before the onset of biodiversity change, suggest that reductions in body size more generally may be a precursor of a subsequent loss of species and turnover at the community level caused by climate change. Sedimentological evidence is against hypoxia as a driver of extinction and the preceding size decrease in the brachiopod fauna in the studied succession, although low oxygen levels are widely held responsible for elevated early Toarcian extinction rates globally. Reduction of mean shell size in brachiopods but stasis in bivalves is difficult to explain with ocean acidification, because experimental work shows that brachiopods can be resilient to lowered pH, albeit long-term metabolic costs and potential evolutionary adaptations are unknown. Rising early Toarcian temperatures in the Lusitanian Basin seem to be a plausible factor in both diversity decline associated with the T-OAE and the preceding reductions in mean shell size, because thermal tolerances in modern bivalves are among the highest within marine invertebrates.