Litsios Glenn, Salamin Nicolas
Department of Ecology and Evolution, Biophore, University of Lausanne, 1015, Lausanne, Switzerland.
Swiss Institute of Bioinformatics, Génopode, Quartier Sorge, 1015, Lausanne, Switzerland.
BMC Evol Biol. 2014 Nov 30;14:245. doi: 10.1186/s12862-014-0245-5.
The importance of hybridisation during species diversification has long been debated among evolutionary biologists. It is increasingly recognised that hybridisation events occurred during the evolutionary history of numerous species, especially during the early stages of adaptive radiation. We study the effect of hybridisation on diversification in the clownfishes, a clade of coral reef fish that diversified through an adaptive radiation process. While two species of clownfish are likely to have been described from hybrid specimens, the occurrence and effect of hybridisation on the clade diversification is yet unknown.
We generate sequences of three mitochondrial genes to complete an existing dataset of nuclear sequences and document cytonuclear discordance at a node, which shows a drastic increase of diversification rate. Then, using a tree-based jack-knife method, we identify clownfish species likely stemming from hybridisation events. Finally, we use molecular cloning and identify the putative parental species of four clownfish specimens that display the morphological characteristics of hybrids.
Our results show that consistently with the syngameon hypothesis, hybridisation events are linked with a burst of diversification in the clownfishes. Moreover, several recently diverged clownfish lineages likely originated through hybridisation, which indicates that diversification, catalysed by hybridisation events, may still be happening.
杂交在物种多样化过程中的重要性长期以来一直是进化生物学家争论的焦点。人们越来越认识到，杂交事件发生在众多物种的进化历史中，尤其是在适应性辐射的早期阶段。我们研究杂交对小丑鱼多样化的影响，小丑鱼是一类通过适应性辐射过程实现多样化的珊瑚礁鱼类。虽然可能已经从小型标本中描述了两种小丑鱼，但杂交对该类群多样化的发生情况和影响尚不清楚。
我们生成了三个线粒体基因的序列，以完善现有的核序列数据集，并记录了一个节点处的细胞核与线粒体基因不一致情况，这显示出多样化速率的急剧增加。然后，使用基于树的刀切法，我们确定了可能源自杂交事件的小丑鱼物种。最后，我们使用分子克隆技术，确定了四个具有杂种形态特征的小丑鱼标本的推定亲本物种。
我们的结果表明，与整合群假说一致，杂交事件与小丑鱼多样化的爆发有关。此外，几个最近分化的小丑鱼谱系可能起源于杂交，这表明由杂交事件催化的多样化可能仍在发生。
