Origin of the Eumetazoa: Testing ecological predictions of molecular clocks against the Proterozoic fossil record
Origin of the Eumetazoa: Testing ecological predictions of molecular clocks against the Proterozoic fossil record
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DOI：
10.1073/pnas.0503660102
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发表时间：
2005-07-05
影响因子：
11.1
通讯作者：
Butterfield, NJ
中科院分区：
文献类型：
--
作者：
Peterson, KJ;Butterfield, NJ
分子钟有可能揭示早期后生动物分歧的时间，但不同的算法和校准点产生明显不一致的结果。我们在这里认为，竞争分子钟假说应该在化石记录中进行测试，原则上，从根本上新的动物组织等级将有生态系统的影响。使用一组7个核编码的蛋白质序列，我们证明了孔类的paraphyly和计算海绵/真后生动物和刺胞动物/bilaterian分歧时间，通过使用两个距离[最小进化（ME）]和最大似然（ML）分子钟; ME括号的外观真后生动物之间的634和604马，而ML建议它是在867和748马之间。值得注意的是，ME，而不是ML，估计是一致的元古宙疑源类记录中的一个主要政权的变化，包括：（i）消失的低多样性，进化静态，前埃迪卡拉纪刺形;（h）辐射的高多样性，短命的陡山沱-Pertatataka微生物群;（iii）一个数量级的进化周转率增加。我们解释这种营业额的结果，伴随着真后生动物神经系统和肠道的进化的新的生态挑战。因此，更容易保存的微体化石记录为埃迪卡拉纪前真后生动物的不存在提供了积极的证据，并强烈支持ME分子钟的准确性，从而支持其更普遍的应用。
Molecular clocks have the potential to shed light on the timing of early metazoan divergences, but differing algorithms and calibration points yield conspicuously discordant results. We argue here that competing molecular clock hypotheses should be testable in the fossil record, on the principle that fundamentally new grades of animal organization will have ecosystem-wide impacts. Using a set of seven nuclear-encoded protein sequences, we demonstrate the paraphyly of Porifera and calculate sponge/eumetazoan and cnidarian/bilaterian divergence times by using both distance [minimum evolution (ME)] and maximum likelihood (ML) molecular clocks; ME brackets the appearance of Eumetazoa between 634 and 604 Ma, whereas ML suggests it was between 867 and 748 Ma. Significantly, the ME, but not the ML, estimate is coincident with a major regime change in the Proterozoic acritarch record, including: (i) disappearance of low-diversity, evolutionarily static, pre-Ediacaran acanthomorphs; (h) radiation of the high-diversity, short-lived Doushantuo-Pertatataka microbiota; and (iii) an order-of-magnitude increase in evolutionary turnover rate. We interpret this turnover as a consequence of the novel ecological challenges accompanying the evolution of the eumetazoan nervous system and gut. Thus, the more readily preserved microfossil record provides positive evidence for the absence of pre-Ediacaran eumetazoans and strongly supports the veracity, and therefore more general application, of the ME molecular clock.