The maximum rate of mammal evolution
The maximum rate of mammal evolution
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DOI：
10.1073/pnas.1120774109
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发表时间：
2012-03-13
影响因子：
11.1
通讯作者：
Uhen, Mark D.
中科院分区：
文献类型：
--
作者：
Evans, Alistair R.;Jones, David;Uhen, Mark D.
哺乳动物能以多快的速度从老鼠大小进化到大象大小？实现如此大的转变需要重大的生物重组。因此，这种变化发生的速度对广泛的动物变化具有重要意义，包括适应性辐射和从大规模灭绝中恢复。为了量化大规模进化的速度，我们开发了一个度量，进化最大速率，它代表了进化中一个特征的最大进化速率。我们将这一指标应用于过去7000万年哺乳动物的体重进化，在此期间，海洋、大陆和岛屿上发生了多次大规模的进化转变。我们的计算表明，陆生哺乳动物的数量分别增加了100倍、1000倍和5000倍，至少需要1.6、5.1和1000万代。鲸鱼的值下降到长度的一半（即110万、300万和500万代），可能是由于生活在水生环境中的机械限制减少了。当考虑到世代时间的差异时，我们发现在白垩纪-古近纪（K-Pg）灭绝事件之后的3500万年里，哺乳动物的最大体重呈指数增长。我们的研究结果还表明了宏观进化的基本不对称性：非常大的减少（如极端岛屿侏儒症）可能以超过10倍的增长速度发生。我们的发现允许对微观进化和宏观进化模式和过程进行更严格的比较。
How fast can a mammal evolve from the size of a mouse to the size of an elephant? Achieving such a large transformation calls for major biological reorganization. Thus, the speed at which this occurs has important implications for extensive faunal changes, including adaptive radiations and recovery from mass extinctions. To quantify the pace of large-scale evolution we developed a metric, clade maximum rate, which represents the maximum evolutionary rate of a trait within a clade. We applied this metric to body mass evolution in mammals over the last 70 million years, during which multiple large evolutionary transitions occurred in oceans and on continents and islands. Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. When differences in generation time are considered, we find an exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous-Paleogene (K-Pg) extinction event. Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases. Our findings allow more rigorous comparisons of microevolutionary and macroevolutionary patterns and processes.