Moleculer Phylogenetic Study of Cichlid Fishes in Africa

坦噶尼喀湖有许多种类极其多样的当地特有鱼类，这些鱼类被归类为12个主要的分类类群，称为部落。对正弦插入数据的分析已经被认为是阐明系统发育关系的有力工具，我们应用这种方法试图澄清这些鱼类之间的这种关系。我们研究了38个正弦的插入模式，其中24个正弦支持三个支系的单系性。其他14个基因座在正弦插入模式方面表现出广泛的不一致性。这些不一致很可能源于适应性辐射时期。这一现象的一个可能解释是，在大约500-1000万年前发生的连续物种形成事件中，对存在或不存在正弦的等位基因进行了广泛的不完全谱系分类。马拉维湖是450多种地方性叶蝉的家园，这提供了一个壮观的适应性辐射的例子。我们确定了6个座位，在马拉维湖所有被调查的特有物种的共同祖先中，明显地通过逆位插入了正弦序列。在另一个基因座上，除大黄鼠外，所有被调查种的特有非Mbuna cichlids都具有唯一的正弦序列。我们还鉴定了一个与非mbuna物种之间存在或不存在正弦序列相关的跨物种多态的基因座。这一结果表明，这一组中的物种之间可能已经或正在发生不完全的谱系分类和/或种间杂交，这可能会导致对系统发育数据的误解，特别是当使用单基因座标记(如线粒体DNA中的序列)进行分析时。

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.