Clarke John T, Lloyd Graeme T, Friedman Matt
Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA 19104-6316; Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom;
Department of Biological Sciences, Faculty of Science, Macquarie University, North Ryde, NSW 2109, Australia.
Proc Natl Acad Sci U S A. 2016 Oct 11;113(41):11531-11536. doi: 10.1073/pnas.1607237113. Epub 2016 Sep 26.
Since Darwin, biologists have been struck by the extraordinary diversity of teleost fishes, particularly in contrast to their closest "living fossil" holostean relatives. Hypothesized drivers of teleost success include innovations in jaw mechanics, reproductive biology and, particularly at present, genomic architecture, yet all scenarios presuppose enhanced phenotypic diversification in teleosts. We test this key assumption by quantifying evolutionary rate and capacity for innovation in size and shape for the first 160 million y (Permian-Early Cretaceous) of evolution in neopterygian fishes (the more extensive clade containing teleosts and holosteans). We find that early teleosts do not show enhanced phenotypic evolution relative to holosteans. Instead, holostean rates and innovation often match or can even exceed those of stem-, crown-, and total-group teleosts, belying the living fossil reputation of their extant representatives. In addition, we find some evidence for heterogeneity within the teleost lineage. Although stem teleosts excel at discovering new body shapes, early crown-group taxa commonly display higher rates of shape evolution. However, the latter reflects low rates of shape evolution in stem teleosts relative to all other neopterygian taxa, rather than an exceptional feature of early crown teleosts. These results complement those emerging from studies of both extant teleosts as a whole and their sublineages, which generally fail to detect an association between genome duplication and significant shifts in rates of lineage diversification.
自达尔文时代以来，生物学家就对硬骨鱼类的非凡多样性感到震惊，尤其是与它们最亲近的“活化石”全骨鱼类亲属形成对比。硬骨鱼类成功的假设驱动因素包括颌骨力学、生殖生物学方面的创新，尤其是目前的基因组结构创新，但所有情况都以硬骨鱼类表型多样化的增强为前提。我们通过量化新鳍鱼类（包含硬骨鱼类和全骨鱼类的更广泛分支）在演化的最初1.6亿年（二叠纪-早白垩世）中大小和形状的进化速率及创新能力，来检验这一关键假设。我们发现，早期硬骨鱼类相对于全骨鱼类并未表现出增强的表型进化。相反，全骨鱼类的进化速率和创新能力常常与硬骨鱼类干群、冠群及整个类群相当，甚至可能超过它们，这与现存全骨鱼类代表的“活化石”声誉不符。此外，我们发现硬骨鱼类谱系内部存在一些异质性的证据。虽然硬骨鱼类干群在发现新体型方面表现出色，但早期冠群类群通常显示出更高的体型进化速率。然而，后者反映的是硬骨鱼类干群相对于所有其他新鳍鱼类类群较低的体型进化速率，而非早期冠群硬骨鱼类的特殊特征。这些结果补充了对现存硬骨鱼类整体及其亚谱系的研究结果，这些研究通常未能检测到基因组复制与谱系多样化速率的显著变化之间存在关联。
