Departamento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC. c/José Gutiérrez Abascal, 2, 28006, Madrid, Spain.
Laboratorio de Biología Acuática, Facultad de Biología, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, Mexico.
BMC Evol Biol. 2018 Nov 20;18(1):173. doi: 10.1186/s12862-018-1286-y.
The Pantosteus plebeius-nebuliferus species-group is a group of freshwater fishes distributed in endo- and exorheic drainage basins in the Mexican Sierra Madre Occidental mountain range system and central North Mexico. The geological history of this region is considered an important factor in explaining the evolutionary history of low vagility animals like freshwaters fishes. The aim of this study was to examine the phylogenetic relationships and describe the evolutionary history of the species-group. We hypothesized that the genetic structure and distribution of the main clades of Pantosteus plebeius-nebuliferus are associated with the geological history of Northern Mexico. To this end, we obtained DNA sequences of mitochondrial and nuclear genes and performed phylogenetic and phylogeographic analyses. Divergence time estimation and ancestral area reconstruction were also carried out to propose a biogeographical hypothesis, and species boundaries within the species-group were also tested.
We identified four clades within the Pantosteus plebeius-nebuliferus species-group in both markers. Divergence ranged from 5.9% to 9.2% for cytb and 0.1% to 0.9% for GHI. We observed significant genetic structure and no shared haplotypes between clades. We estimated that the clades diverged during the last 5.1 Myr, with a biogeographic scenario suggesting eight vicariant and four dispersal events through the historic range of the species-group. We found that the best species-delimitation model is when four species are assumed, which correspond to the main clades. We identified nine evolutionary significance units (ESUs), pertinent to the conservation of the group, each representing populations present in distinct drainage basins.
The evolutionary history of the Pantosteus plebeius-nebuliferus species-group is characterized by vicariant post-dispersal processes, linked to geological changes in the Sierra Madre Occidental and central Northern Mexico since the Pliocene. This is congruent with biogeographic patterns described for other co-distributed fish species. We propose a new phylogenetic hypothesis for the species-group, clarifying the taxonomy of this evolutionarily complex group. Our results suggest that the species-group consists of at least four clades with independent evolutionary histories, two of which may represent new undescribed species. Our identification of ESUs provides a basis upon which conservation measures can be developed for the species-group.
Pantosteus plebeius-nebuliferus 物种群是一组分布在墨西哥西马德雷山脉系统的内陆和外陆流域以及中北美北部的淡水鱼类。该地区的地质历史被认为是解释像淡水鱼类这样低迁移性动物进化历史的重要因素。本研究的目的是检验物种群的系统发育关系并描述其进化历史。我们假设 Pantosteus plebeius-nebuliferus 的主要分支的遗传结构和分布与墨西哥北部的地质历史有关。为此，我们获得了线粒体和核基因的 DNA 序列，并进行了系统发育和系统地理学分析。还进行了分歧时间估计和祖区重建，以提出一个生物地理学假说，并检验了物种群内的物种边界。
在两种标记物中，我们在 Pantosteus plebeius-nebuliferus 物种群中鉴定出了四个分支。细胞色素 b 的分歧范围为 5.9%至 9.2%，GHI 的分歧范围为 0.1%至 0.9%。我们观察到了显著的遗传结构，并且分支之间没有共享的单倍型。我们估计，分支在过去的 5.1 百万年间发生了分歧，生物地理情景表明，有八个隔离事件和四个扩散事件发生在该物种群的历史分布范围内。我们发现，最佳的物种界定模型是假设存在四个物种，这与主要分支相对应。我们确定了九个进化意义单位 (ESU)，与该群体的保护有关，每个单位代表分布在不同流域的种群。
Pantosteus plebeius-nebuliferus 物种群的进化历史以隔离后扩散过程为特征，这与上新世以来西马德雷山脉和中北美北部的地质变化有关。这与其他共生鱼类的生物地理模式一致。我们提出了该物种群的一个新的系统发育假说，澄清了这个进化复杂的群体的分类学。我们的结果表明，该物种群至少由四个具有独立进化历史的分支组成，其中两个分支可能代表新的未描述的物种。我们对 ESU 的识别为制定该物种群的保护措施提供了基础。
