EARLY VERTEBRATE EVOLUTION
EARLY VERTEBRATE EVOLUTION
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DOI：
10.1111/pala.12125
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发表时间：
2014-09-01
期刊：
影响因子：
2.6
通讯作者：
Keating, Joseph N.
中科院分区：
文献类型：
--
作者：
Donoghue, Philip C. J.;Keating, Joseph N.
几个世纪以来，关于脊椎动物的起源和进化的争论一直困扰着生物学家和古生物学家。分子系统发育学解决了脊椎动物在无脊椎脊索动物亲属中的地位，以及脊索动物在后口动物亲属中的地位。脊椎动物的起源以广泛的基因组学、胚胎学和表型进化变化为特征。基于现存谱系的分析表明，脊椎动物和颌口动物起源的进化速度发生了巨大变化，与全基因组复制事件相一致。然而，化石记录提供的丰富视角表明，这些明显的解剖进化和分类丰富度的爆发是系统发育中间物种灭绝的人工产物，这些中间物种的化石仍然证明了冠齿龙特征的逐渐聚集。对早期脊椎动物进化的时间、节奏和模式的更精确的理解取决于：(1)更好的活环口动物基因组组装；(2)对主要化石类群的解剖特征有了更深入的认识，特别是无肢纲、齿形纲、galeaspiids和pituriaspids；(3)传统群体的单一性检验；(4)应用发散时间方法，不仅整合了现存物种的分子数据，还整合了形态数据和灭绝物种的数据。由此产生的框架将提供对特征进化和多样化速度的严格测试，以及对生态进化长期趋势的假设的严格测试，这些假设本身因缺乏数量功能测试而受到影响。化石记录对无颌脊椎动物向有颌脊椎动物过渡的本质一直保持沉默，有颌脊椎动物自古生代中期以来一直占主导地位。对这一最具形成性的事件的解释可能取决于我们提出的对早期脊椎动物系统分类学的全面检查，但也许更根本的是等待发现的化石等级。
Debate over the origin and evolution of vertebrates has occupied biologists and palaeontologists alike for centuries. This debate has been refined by molecular phylogenetics, which has resolved the place of vertebrates among their invertebrate chordate relatives, and that of chordates among their deuterostome relatives. The origin of vertebrates is characterized by wide-ranging genomic, embryologic and phenotypic evolutionary change. Analyses based on living lineages suggest dramatic shifts in the tempo of evolutionary change at the origin of vertebrates and gnathostomes, coincident with whole-genome duplication events. However, the enriched perspective provided by the fossil record demonstrates that these apparent bursts of anatomical evolution and taxic richness are an artefact of the extinction of phylogenetic intermediates whose fossil remains evidence the gradual assembly of crown gnathostome characters in particular. A more refined understanding of the timing, tempo and mode of early vertebrate evolution rests with: (1) better genome assemblies for living cyclostomes; (2) a better understanding of the anatomical characteristics of key fossil groups, especially the anaspids, thelodonts, galeaspids and pituriaspids; (3) tests of the monophyly of traditional groups; and (4) the application of divergence time methods that integrate not just molecular data from living species, but also morphological data and extinct species. The resulting framework will provide for rigorous tests of rates of character evolution and diversification, and of hypotheses of long-term trends in ecological evolution that themselves suffer for lack of quantitative functional tests. The fossil record has been silent on the nature of the transition from jawless vertebrates to the jawed vertebrates that have dominated communities since the middle Palaeozoic. Elucidation of this most formative of episodes likely rests with the overhaul of early vertebrate systematics that we propose, but perhaps more fundamentally with fossil grades that await discovery.