Institute of Biology, Federal University of Bahia, Salvador, Brazil.
Department of Ecology and Evolutionary Biology, Museum of Zoology, University of Michigan, Ann Arbor, MI, USA.
J Evol Biol. 2020 Nov;33(11):1530-1542. doi: 10.1111/jeb.13689. Epub 2020 Aug 30.
Understanding the structure of hybrid zones provides valuable insights about species boundaries and speciation, such as the evolution of barriers to gene flow and the strength of selection. In river networks, studying evolutionary processes in hybrid zones can be especially challenging, given the influence of past and current river properties along with biological species-specific traits. Here, we suggest that a natural hybrid zone between two divergent lineages of the sexually dimorphic Neotropical fish Nematocharax venustus was probably established by secondary contact as a result of a river capture event between the Contas and Pardo river basins. This putative river capture is supported by hydrogeological evidence of elbows of capture, wind gaps and geological faults. The morphological (colour pattern) and genetic (mtDNA and RADseq) variation reveal a clinal transition between parental lineages along the main river, with predominance of F2 hybrids at the centre of the hybrid zone, absence of early generation backcrosses and different levels of hybridization in the tributaries. We highlight that different sources of information are crucial for understanding how the riverscape spatial history influences the connectivity between and within river systems and, consequently, the dynamics of gene flow between freshwater lineages/species.
了解杂种区的结构为物种界限和物种形成提供了有价值的见解，例如基因流障碍的进化和选择的强度。在河流网络中，考虑到过去和当前河流特性以及生物特定物种特征的影响，研究杂种区的进化过程可能特别具有挑战性。在这里，我们提出，两性异形的新热带鱼类 Nematocharax venustus 的两个分歧谱系之间的自然杂种区可能是由于 Contas 和 Pardo 流域之间的河流捕获事件而通过二次接触建立的。这种假定的河流捕获得到了水力地质证据的支持，包括捕获肘、风隙和地质断层。形态（颜色模式）和遗传（mtDNA 和 RADseq）变异沿主要河流显示出亲代谱系之间的渐变过渡，杂种区中心以 F2 杂种为主，不存在早期世代的回交，支流中的杂交程度也不同。我们强调，不同来源的信息对于理解河流景观空间历史如何影响河流系统之间和内部的连通性以及淡水谱系/物种之间基因流的动态至关重要。
