Department of Biology, University of Konstanz, Konstanz, Germany.
Department of Ecology & Evolutionary Biology, University of California, Los Angeles, CA, USA.
BMC Evol Biol. 2018 Nov 29;18(1):179. doi: 10.1186/s12862-018-1296-9.
Phylogenies provide critical information about convergence during adaptive radiation. To test whether there have been multiple origins of a distinctive trophic phenotype in one of the most rapidly radiating groups known, we used ultra-conserved elements (UCEs) to examine the evolutionary affinities of Lake Malawi cichlids lineages exhibiting greatly hypertrophied lips.
The hypertrophied lip cichlids Cheilochromis euchilus, Eclectochromis ornatus, Placidochromis "Mbenji fatlip", and Placidochromis milomo are all nested within the non-mbuna clade of Malawi cichlids based on both concatenated sequence and single nucleotide polymorphism (SNP) inferred phylogenies. Lichnochromis acuticeps that exhibits slightly hypertrophied lips also appears to have evolutionary affinities to this group. However, Chilotilapia rhoadesii that lacks hypertrophied lips was recovered as nested within the species Cheilochromis euchilus. Species tree reconstructions and analyses of introgression provided largely ambiguous patterns of Malawi cichlid evolution.
Contrary to mitochondrial DNA phylogenies, bifurcating trees based on our 1024 UCE loci supported close affinities of Lake Malawi lineages with hypertrophied lips. However, incomplete lineage sorting in Malawi tends to render these inferences more tenuous. Phylogenomic analyses will continue to provide powerful inferences about whether phenotypic novelties arose once or multiple times during adaptive radiation.
系统发育为适应性辐射过程中的趋同进化提供了重要信息。为了检验在已知辐射速度最快的鱼类群之一中是否存在独特的营养表型的多次起源，我们使用超保守元件（UCEs）来研究表现出极度肥大唇的马拉维慈鲷鱼类进化亲缘关系。
根据串联序列和单核苷酸多态性（SNP）推断的系统发育，肥大唇慈鲷鱼 Cheilochromis euchilus、Eclectochromis ornatus、Placidochromis“Mbenji fatlip”和 Placidochromis milomo 都嵌套在马拉维慈鲷鱼的非 mbuna 分支中。表现出略微肥大唇的 Lichnochromis acuticeps 似乎也与该组具有进化亲缘关系。然而，没有肥大唇的 Chilotilapia rhoadesii 被归入 Cheilochromis euchilus 种内。种系树重建和基因渗入分析提供了马拉维慈鲷鱼进化的模式。
与线粒体 DNA 系统发育相反，基于我们的 1024 个 UCE 位点的分支树支持马拉维湖唇线具有密切的亲缘关系。然而，马拉维的不完全谱系分选往往使这些推断更加脆弱。系统基因组分析将继续提供有关表型新颖性是在适应性辐射过程中一次还是多次出现的有力推断。
