Laboratório de Ictiologia, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul - UFRGS, Av. Bento Gonçalves, 9500, Bloco 4, prédio 43.435, 91501-970 Porto Alegre, RS, Brazil.
Laboratório de Ictiologia, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul - UFRGS, Av. Bento Gonçalves, 9500, Bloco 4, prédio 43.435, 91501-970 Porto Alegre, RS, Brazil; Laboratório de Sistemática Molecular-Beagle, Departamento de Biologia Animal, Universidade Federal de Viçosa - UFV, Av. Ph. Rolfs, sn, Anexo II CCB, 36570-000 Viçosa, MG, Brazil.
Mol Phylogenet Evol. 2019 Nov;140:106604. doi: 10.1016/j.ympev.2019.106604. Epub 2019 Aug 27.
The pike-characin Oligosarcus is a group of Characidae composed of 22 species, which have mostly allopatric distributed species in southeastern South America and sympatric occurrence of few species. Oligosarcus shares a similar distribution pattern with other fish genera and therefore, can help us to understand biogeographic events that influenced freshwater fish distribution in the southeastern South America. Our paper presents the most extensive taxonomic coverage for molecular analysis of Oligosarcus and uses various methods to examine the evolutionary history of the genus. Phylogenetic relationships among species of Oligosarcus were examined using a multilocus dataset by Maximum Likelihood and Bayesian methods. A relaxed molecular clock was used to estimate lineage divergence times, which provide a framework to examine the biogeographic history of this clade across the drainage basins of southeastern South America. Oligosarcus was resolved as monophyletic with strong support, and related to lineages currently assigned to the genus Astyanax. Within Oligosarcus, two groups of approximately equal species richness were resolved as monophyletic, mainly restricted to continental and coastal drainages of southeastern South America. Oligosarcus radiation is estimated to the late Neogene, with its origin in the Pliocene and most speciation events occurring in the Pleistocene. Some apomorphic characteristics associated with piscivory (e.g. large caniniform teeth) in Oligosarcus likely have evolved once, and are convergent to similar phenotypes observed in a distantly related clade of Astyanax (formerly Bramocharax). In addition, the presence of morphological convergence within the genus Oligosarcus (e.g. trophic morphology) seems to explain the difference between the present molecular hypothesis and some previous morphological studies. Ancestral geographical range estimation using analytical methods (e.g. DIVALIKE and DEC) demonstrated the effects of different Landscape Evolution Models (LEMs) on diversification of Oligosarcus. The results suggest that the two main Oligosarcus clades evolved in allopatry in continental and coastal drainages, with subsequent range extension and vicariance events that established the modern distributions. LEM analyses indicate the importance of formation of riverine barriers across the watershed of the La Plata basin and the effects of sea-level changes during the Pleistocene for delineating lineage distributions of Oligosarcus.
南美脂鲤属是脂鲤科的一个由 22 个物种组成的群组，这些物种主要分布在南美洲东南部的不同地区，也有少数物种共同分布。南美脂鲤属与其他鱼类属具有相似的分布模式，因此可以帮助我们了解影响南美洲东南部淡水鱼类分布的生物地理事件。我们的论文展示了对南美脂鲤属进行分子分析的最广泛的分类学覆盖范围，并使用各种方法来研究该属的进化历史。使用最大似然法和贝叶斯法通过多基因数据集来检验物种间的系统发育关系。使用松弛分子钟来估计谱系分化时间，为检验该分支在南美洲东南部水系中的生物地理历史提供了一个框架。南美脂鲤属被确定为单系群，具有很强的支持，与目前分配给 Astyanax 属的谱系有关。在南美脂鲤属中，两个具有大致相等物种丰富度的类群被确定为单系群，主要局限于南美洲东南部的大陆和沿海流域。南美脂鲤属的辐射估计发生在晚中新世，起源于上新世，大多数物种形成事件发生在更新世。南美脂鲤属中与肉食性相关的一些特化特征（例如大犬齿状的牙齿）可能是一次进化而来的，与 Astyanax 属的一个远缘分支（以前称为 Bramocharax）中观察到的相似表型趋同。此外，在南美脂鲤属内存在形态趋同（例如营养形态），这似乎可以解释目前的分子假说与一些先前的形态学研究之间的差异。使用分析方法（例如 DIVALIKE 和 DEC）进行祖先地理范围估计，证明了不同景观演化模型（LEMs）对南美脂鲤属多样化的影响。结果表明，两个主要的南美脂鲤属类群在大陆和沿海流域的异域进化，随后发生了范围扩展和隔离事件，从而建立了现代分布。LEM 分析表明，拉普拉塔河流域水系中形成河流屏障以及更新世海平面变化对划定南美脂鲤属谱系分布的重要性。
