Santini Francesco, Harmon Luke J, Carnevale Giorgio, Alfaro Michael E
Department of Ecology and Evolutionary Biology, University of California at Los Angeles, 651 Charles Young Dr, South, Los Angeles, CA 90095, USA.
BMC Evol Biol. 2009 Aug 8;9:194. doi: 10.1186/1471-2148-9-194.
One of the main explanations for the stunning diversity of teleost fishes (approximately 29,000 species, nearly half of all vertebrates) is that a fish-specific whole-genome duplication event (FSGD) in the ancestor to teleosts triggered their subsequent radiation. However, one critical assumption of this hypothesis, that diversification rates in teleosts increased soon after the acquisition of a duplicated genome, has never been tested.
Here we show that one of three major diversification rate shifts within ray-finned fishes occurred at the base of the teleost radiation, as predicted by the FSGD hypothesis. We also find evidence for two rate increases that are much younger than the inferred age of the FSGD: one in the common ancestor of most ostariophysan fishes, and a second one in the common ancestor of percomorphs. The biodiversity contained within these two clades accounts for more than 88% of living fish species.
Teleosts diversified explosively in their early history and this burst of diversification may have been caused by genome duplication. However, the FSGD itself may be responsible for a little over 10% of living teleost biodiversity. ~88% of species diversity is derived from two relatively recent radiations of freshwater and marine fishes where genome duplication is not suspected. Genome duplications are a common event on the tree of life and have been implicated in the diversification of major clades like flowering plants, vertebrates, and gnathostomes. However our results suggest that the causes of diversification in large clades are likely to be complex and not easily ascribed to a single event, even a dramatic one such as a whole genome duplication.
硬骨鱼（约29000种，几乎占所有脊椎动物的一半）惊人的多样性的主要解释之一是，硬骨鱼祖先中发生的一次鱼类特异性全基因组复制事件（FSGD）引发了它们随后的辐射演化。然而，这一假说的一个关键假设，即硬骨鱼在获得复制基因组后不久多样化速率就增加了，从未得到验证。
在这里我们表明，辐鳍鱼三大主要多样化速率转变之一发生在硬骨鱼辐射演化的基部，正如FSGD假说所预测的那样。我们还发现了两次速率增加的证据，它们比推断的FSGD年龄要年轻得多：一次发生在大多数骨鳔鱼类的共同祖先中，另一次发生在鲈形目鱼类的共同祖先中。这两个分支中包含的生物多样性占现存鱼类物种的88%以上。
硬骨鱼在其早期历史中经历了爆发式的多样化，这种多样化的爆发可能是由基因组复制引起的。然而，FSGD本身可能只对略多于10%的现存硬骨鱼生物多样性负责。约88%的物种多样性来自淡水鱼和海水鱼的两次相对较新的辐射演化，而这两次辐射演化并未怀疑有基因组复制现象。基因组复制在生命之树上是一个常见事件，并且与开花植物、脊椎动物和有颌类等主要类群的多样化有关。然而，我们的结果表明，大类群多样化的原因可能很复杂，不容易归因于单一事件，即使是像全基因组复制这样剧烈的事件。
