Salzburger Walter
Zoological Institute, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland.
Mol Ecol. 2009 Jan;18(2):169-85. doi: 10.1111/j.1365-294X.2008.03981.x. Epub 2008 Nov 4.
The question of how genetic variation translates into organismal diversity has puzzled biologists for decades. Despite recent advances in evolutionary and developmental genetics, the mechanisms that underlie adaptation, diversification and evolutionary innovation remain largely unknown. The exceptionally diverse species flocks of cichlid fishes are textbook examples of adaptive radiation and explosive speciation and emerge as powerful model systems to study the genetic basis of animal diversification. East Africa's hundreds of endemic cichlid species are akin to a natural mutagenesis screen and differ greatly not only in ecologically relevant (hence naturally selected) characters such as mouth morphology and body shape, but also in sexually selected traits such as coloration. One of the most fascinating aspects of cichlid evolution is the frequent occurrence of evolutionary parallelisms, which has led to the question whether selection alone is sufficient to produce these parallel morphologies, or whether a developmental or genetic bias has influenced the direction of diversification. Here, I review fitness-relevant traits that could be responsible for the cichlids' evolutionary success and assess whether these were shaped by sexual or natural selection. I then focus on the interaction and the relative importance of sexual vs. natural selection in cichlid evolution. Finally, I discuss what is currently known about the genes underlying the morphogenesis of adaptively relevant traits and highlight the importance of the forthcoming cichlid genomes in the quest of the genetic basis of diversification in this group.
几十年来，基因变异如何转化为生物多样性的问题一直困扰着生物学家。尽管进化遗传学和发育遗传学最近取得了进展，但适应、多样化和进化创新背后的机制在很大程度上仍然未知。丽鱼科鱼类异常多样的物种群是适应性辐射和爆发性物种形成的典型例子，也是研究动物多样化遗传基础的强大模型系统。东非的数百种特有丽鱼科物种类似于一个自然诱变筛选，不仅在口部形态和体型等与生态相关（因此是自然选择的）特征上有很大差异，而且在诸如体色等性选择特征上也有很大差异。丽鱼科进化中最引人入胜的一个方面是进化平行现象的频繁发生，这引发了一个问题，即仅靠选择是否足以产生这些平行形态，或者发育或遗传偏差是否影响了多样化的方向。在这里，我回顾了可能导致丽鱼科进化成功的与适应性相关的特征，并评估这些特征是由性选择还是自然选择塑造的。然后，我将重点关注性选择与自然选择在丽鱼科进化中的相互作用及其相对重要性。最后，我将讨论目前已知的与适应性相关特征形态发生的基因，并强调即将出现的丽鱼科基因组在探索该类群多样化遗传基础方面的重要性。
