School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia; Earth Sciences Section, South Australian Museum, North Terrace, Adelaide 5000, Australia.
Curr Biol. 2013 Oct 7;23(19):1889-95. doi: 10.1016/j.cub.2013.07.055. Epub 2013 Sep 12.
The near-simultaneous appearance of most modern animal body plans (phyla) 530 million years ago during the Cambrian explosion is strong evidence for a brief interval of rapid phenotypic and genetic innovation, yet the exact speed and nature of this grand adaptive radiation remain debated. Crucially, rates of morphological evolution in the past (i.e., in ancestral lineages) can be inferred from phenotypic differences among living organisms-just as molecular evolutionary rates in ancestral lineages can be inferred from genetic divergences. We here employed Bayesian and maximum likelihood phylogenetic clock methods on an extensive anatomical and genomic data set for arthropods, the most diverse phylum in the Cambrian and today. Assuming an Ediacaran origin for arthropods, phenotypic evolution was ~4 times faster, and molecular evolution ~5.5 times faster, during the Cambrian explosion compared to all subsequent parts of the Phanerozoic. These rapid evolutionary rates are robust to assumptions about the precise age of arthropods. Surprisingly, these fast early rates do not change substantially even if the radiation of arthropods is compressed entirely into the Cambrian (542 mega-annum [Ma]) or telescoped into the Cryogenian (~650 Ma). The fastest inferred rates are still consistent with evolution by natural selection and with data from living organisms, potentially resolving "Darwin's dilemma." However, evolution during the Cambrian explosion was unusual (compared to the subsequent Phanerozoic) in that fast rates were present across many lineages.
大约 5.3 亿年前，在寒武纪生命大爆发时期，大多数现代动物体节（门）几乎同时出现，这有力地证明了在一个短暂的时间间隔内，出现了快速的表型和遗传创新，但这种宏伟的适应性辐射的确切速度和性质仍存在争议。至关重要的是，过去（即在祖先谱系中）的形态进化速度可以从现存生物之间的表型差异推断出来——就像祖先谱系中的分子进化速度可以从遗传分歧推断出来一样。我们在这里对节肢动物的广泛解剖学和基因组数据集，采用贝叶斯和最大似然系统发育钟方法进行研究，节肢动物是寒武纪和今天最具多样性的门。假设节肢动物起源于埃迪卡拉纪，那么与显生宙的所有后续部分相比，在寒武纪大爆发期间，表型进化的速度要快约 4 倍，分子进化的速度要快约 5.5 倍。这些快速的进化率在假设节肢动物的确切年龄方面是稳健的。令人惊讶的是，即使将节肢动物的辐射完全压缩到寒武纪（约 542 百万年[Ma]）或压缩到冰川纪（约 650 Ma），这些早期的快速进化率也不会有太大变化。推断出的最快速度仍然与自然选择进化和来自现存生物的数据一致，这可能解决了“达尔文的困境”。然而，与随后的显生宙相比，寒武纪大爆发时期的进化是不寻常的（与随后的显生宙相比），因为许多谱系中都存在快速的进化速度。
