Moleculer Phylogenetic Study of Cichlid Fishes in Africa

坦噶尼喀湖拥有许多非常多样化的慈鲷鱼的特有物种，这些鱼类被分为12个主要的分类群，称为部落。SINE插入数据的分析已被公认为是一个强大的工具，阐明系统发育关系，我们应用这种方法，试图澄清这些慈鲷之间的关系。我们研究了38个SINE的插入模式，其中24个支持3个分支的单系性。其他14个位点的SINE插入模式显示了广泛的不一致性。这些不一致很可能源于适应性辐射期。这一现象的一个可能的解释是，在大约500 - 1000万年前发生的连续物种形成事件中，等位基因的存在或不存在的广泛的不完整谱系分类。马拉维湖是450多种特有慈鲷的家园，这提供了适应性辐射的壮观例子。我们确定了6个位点，在该位点上，一个SINE序列显然已被特异性地插入到马拉维湖特有慈鲷科所有调查物种的共同祖先中。在另一个位点，独特的共享的SINE序列是显而易见的地方性非Mbuna慈鲷属的所有调查物种与例外的Rhamphochromis SP。我们还表征了一个位点，表现出跨物种的多态性相对于非Mbuna物种之间的SINE序列的存在或不存在。这一结果表明，不完整的谱系排序和/或种间杂交可能已经发生或正在发生的物种在这个组中，这可能会导致误解的系统发育数据，特别是当一个单一的基因座标记，如在线粒体DNA序列，用于分析。

Lake Tanganyika harbors numerous endemic species of extremely diverse cichlid fish that have been classified into twelve major taxonomic groups known as tribes. Analysis of SINE insertion data has been acknowledged as a powerful tool for the elucidation of phylogenetic relationships, and we applied this method in an attempt to clarify such relationships among these cichlids. We studied insertion patterns of 38 SINEs in total, 24 of which supported the monophyly of three clades. The other 14 loci revealed extensive incongruence in terms of the patterns of SINE insertions. These incongruence most likely stems from period of adaptive radiation. One possible explanation for this phenomenon in the extensive incomplete lineage sorting of alleles for the presence or absence of a SINE during successive speciation events during this period which took place about 5-10 million years ago.Lake Malawi is home to more than 450 species of endemic cichlids, which provide a spectacular example of adaptive radiation. We identified six loci at which a SINE sequence had apparently been specifically inserted by retroposition in the common ancestor of all the investigated species of endemic cichlids in Lake Malawi. At another locus, unique sharing of a SINE sequence was evident among all the investigated species of endemic non-Mbuna cichlids with the exception of Rhamphochromis sp. We also characterized a locus that exhibited transspecies polymorphism with respect to the presence or absence of the SINE sequence among non-Mbuna species. This result suggests that incomplete lineage sorting and/or interspecific hybridization might have occurred or be occurring among the species in this group, which might potentially cause misinterpretation of phylogenetic data, in particular when a single-locus marker, such as a sequence in the mitochondrial DNA, is used for analysis.