Genetic diversity within the genus Cynotilapia and its phylogenetic position among Lake Malawi’s mbuna cichlids
Genetic diversity within the genus Cynotilapia and its phylogenetic position among Lake Malawi’s mbuna cichlids
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发表时间：
2005
影响因子：
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通讯作者：
D. Kassam;Shingo Seki;B. Rusuwa;A. Ambali;K. Yamaoka
中科院分区：
文献类型：
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作者：
D. Kassam;Shingo Seki;B. Rusuwa;A. Ambali;K. Yamaoka
Cynotilapia的单尖牙是用来将其与所有其他mbuna属区分开来的独特特征，这让进化生物学家们想知道，在mbuna cichlids中，哪一个是与这个属最接近的亲戚。在10-13个种/分类群中，这个属只有两个已描述的种，因此，未描述的分类群要么通过它们的颜色或它们出现的地方而被知道。利用AFLP遗传标记技术确定了罗非鱼的系统发育地位和该属内的遗传多样性。用Nei‘s遗传距离、多态座位频率和平均杂合度来揭示遗传多样性。Neighour-Join(新泽西州)树状图显示，Maylandia属与Cynotilapia的亲缘关系最近。在所有未描述的分类群对之间的遗传距离比两个种之间的遗传距离更高(非洲鲤鱼vs.axelrodi)。在未描述的类群中，多态基因座的频率和平均杂合度也高于两个物种。这些结果，再加上这些分类群之间已知的表型差异(包括颜色，这是通过性别选择形成物种的关键因素)，确实为分类学家提供了一个强大的基础，他们可以正式地将这些分类群描述为物种。未发现的遗传分化对于保护这种特有的鱼类区系非常重要。
Cynotilapia’s unicuspid teeth, a unique character used to delineate it from all other mbuna genera, leaves evolutionary biologists wondering which is the closest relative to this genus among mbuna cichlids. This genus has only two described species out of the 10-13 species/taxa, whereby the undescribed taxa are either known by their colouration or place where they occur. AFLP genetic marker was used to determine the phylogenetic position of Cynotilapia among the mbuna and also the genetic diversity within this genus. Nei’s genetic distance, frequency of polymorphic loci and average heterozygosity were used to unravel the genetic diversity. The neighbour-joining (NJ) dendrogram revealed that the genus Maylandia is the closest relative to Cynotilapia. Genetic distances were higher among all pairs of undescribed taxa than between the two species (Cynotilapia afra vs. C. axelrodi). Frequency of polymorphic loci and average heterozygosity were also higher within undescribed taxa than in two species. These results, coupled with already known phenotypic differences among these taxa (including colour, a crucial factor in speciation through sexual selection), do provide a strong base to taxonomists who can formally describe these taxa as species. The uncovered genetic differentiation is very important for conservation of this endemic fish fauna.