Genomic Signature of an Avian Lilliput Effect across the K-Pg Extinction
Genomic Signature of an Avian Lilliput Effect across the K-Pg Extinction
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DOI：
10.1093/sysbio/syx064
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发表时间：
2018-01-01
影响因子：
6.5
通讯作者：
Field, Daniel J.
中科院分区：
文献类型：
--
作者：
Berv, Jacob S.;Field, Daniel J.
大规模迁移后的幸存者可能与体型的减小有关，这种现象称为小人国效应。身体大小是许多生活史特征（LHT）的强预测因子，并且已知会影响人口统计学和内在生物学过程。因此，整个地球历史上生物体大小的显着变化可能与随之而来的全基因组进化速率的变化有关。在这里，我们报告了一个大规模的禽流感基因组数据集的分子进化率（变化高达20倍）的显着异质性，并表明核苷酸取代率与身体大小和代谢率密切相关。我们还确定了潜在的身体大小减少与古近纪（K-Pg）的过渡，符合小人国效应在大规模灭绝事件之后。我们认为，选择减少身体大小跨越theK-Pg灭绝地平线可能会导致暂时增加替代率沿着最深的分支现存的鸟类生命树。这种“隐藏的”速率加速可能导致严格和宽松的分子钟都高估了禽冠群的年龄，通过与分子取代速率成比例的生活史和人口统计参数之间的关系。如果身体大小的减少（和/或选择相关的人口统计参数，如短世代时间）是大规模灭绝幸存下来的血统的共同属性，这种现象可能有助于解决整个生命树中持续存在的分歧时间争论。此外，我们的研究结果表明，选择某些LHT可能与确定性的分子进化结果。
Survivorship following major mass extinctions may be associated with a decrease in body size-a phenomenon called the Lilliput Effect. Body size is a strong predictor of many life history traits (LHTs), and is known to influence demography and intrinsic biological processes. Pronounced changes in organismal size throughout Earth history are therefore likely to be associated with concomitant genome-wide changes in evolutionary rates. Here, we report pronounced heterogeneity in rates of molecular evolution (varying up to similar to 20-fold) across a large-scale avian phylogenomic data set and show that nucleotide substitution rates are strongly correlated with body size and metabolic rate. We also identify potential body size reductions associated with the Cretaceous-Paleogene (K-Pg) transition, consistent with a Lilliput Effect in the wake of that mass extinction event. We posit that selection for reduced body size across theK-Pg extinction horizon may have resulted in transient increases in substitution rate along the deepest branches of the extant avian tree of life. This "hidden" rate acceleration may result in both strict and relaxed molecular clocks over-estimating the age of the avian crown group through the relationship between life history and demographic parameters that scale with molecular substitution rate. If reductions in body size (and/or selection for related demographic parameters like short generation times) are a common property of lineages surviving mass extinctions, this phenomenon may help resolve persistent divergence time debates across the tree of life. Furthermore, our results suggest that selection for certain LHTs may be associated with deterministic molecular evolutionary outcomes.