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首页> 外文期刊>Molecular phylogenetics and evolution >Patterns of diversification in the discus fishes (Symphysodon spp. Cichlidae) of the Amazon basin
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Patterns of diversification in the discus fishes (Symphysodon spp. Cichlidae) of the Amazon basin

机译：亚马孙河流域铁饼鱼（Symphysodon spp。Cichlidae）的多样化模式

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摘要

We carried out a phylogeograhic and population genetic analysis of fishes of the taxonomically contentious genus Symphysodon from the Amazon basin in order to test hypotheses of relationships among taxonomic units, and potential processes driving diversification within this genus. We sampled 334 individuals of the genus Symphysodon from 24 localities that span the complete geographic distribution of this genus. The sampling scheme included all known phenotypic groups, species and subspecies. Analyses were based on 474 bp of the mitochondrial control region and 1443 bp of the exon 3 of RAG I gene. We observed 102 mtDNA haplotypes defined by 89 segregating sites, and 5 nuDNA alleles defined by three segregating sites. Maximum-likelihood, Bayesian-inference and statistical parsimony analyses revealed three well defined monophyletic groups. These clades corresponded to the 'green' and 'blue' groups of Symphysodon aequifasciatus, and to a previously morphologically unrecognized clade from the Xingu River drainage. These three clades were nested within a paraphyletic assemblage consisting of the 'brown' group of S. aequifasciatus and of both described subspecies of S. discus, the 'Heckel' and the 'abacaxi' discus. Nuclear allele sharing was observed among groups, but there were significant differences in frequencies. We inferred several processes including past fragmentation among groups, and restricted gene flow with isolation by distance within the paraphyletic 'brown + Heckel + abacaxi' groups, and suggest that differences among the 'blue', 'Heckel' and 'brown' groups are potentially maintained by differences in water chemistry preferences. We further inferred colonization of the western Amazon basin by an ancestor of the 'green' clade. The 'green' group was the only group with a pattern of haplotype distribution consistent of a demographic expansion, and the divergence of this clade from other groups of discus was consistent with recent geologic evidence an the breach of the Purus Arch which separates western Amazon from eastern Amazon. We further hypothesized that the differentiation of the 'Xingu' clade could be due to vicariance events resulting from Pleistocene sea level, and thus Amazon River level fluctuations. We discuss the bearings of our results on the current taxonomy of this group, and on the biological reality of the different forms, subspecies and species of Symphysodon concluding that we are probably observing a process of diversification, and therefore taxonomy will remain contentious. (C) 2008 Elsevier Inc. All rights reserved.
机译：我们对来自亚马逊流域的分类学上有争议的Syphysodon属鱼类进行了系统地理学和种群遗传学分析，以检验分类学单元之间的关系以及推动该属多样化的潜在过程的假设。我们从24个地区采样了334个Symphysodon属个体，这些个体遍布该属的完整地理分布。抽样方案包括所有已知的表型群，物种和亚种。分析基于RAG I基因的线粒体控制区的474 bp和外显子3的1443 bp。我们观察到由89个分离位点定义的102个mtDNA单倍型，以及由三个分离位点定义的5个nuDNA等位基因。最大似然，贝叶斯推断和统计简约分析揭示了三个定义明确的单系群体。这些进化枝对应于拟南芥的“绿色”和“蓝色”群，以及新谷河排水系统先前未识别的进化枝。这三个进化枝被嵌套在一个生物共生的组合中，该组合由aequifasciatus的“棕色”群和描述的S. discus亚种，“ Heckel”和“ abacaxi”铁饼组成。在各组之间观察到核等位基因共享，但是频率存在显着差异。我们推断了多个过程，包括各组之间过去的分裂，以及通过共生关系的“棕色+ Heckel + abacaxi”组之间的距离隔离而限制了基因流，并暗示了“蓝色”，“ Heckel”和“棕色”组之间的差异是潜在的维持水化学偏好的差异。我们进一步推断出“绿色”进化枝的祖先对亚马逊河西部盆地的殖民化。 “绿色”群体是唯一具有与人口膨胀相一致的单倍型分布模式的群体，并且该进化枝与其他铁饼群体的差异与最近的地质证据相一致，即将西亚马逊河与亚马逊东部。我们进一步假设，“兴古”进化枝的分化可能是由于更新世海平面引起的偏差事件，以及亚马逊河水位的波动所致。我们讨论了我们的结果对这一组当前分类法的影响，以及对Symphysodon的不同形式，亚种和物种的生物学现实的影响，并得出结论，我们可能正在观察多样化的过程，因此分类法将继续引起争议。 （C）2008 Elsevier Inc.保留所有权利。

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