Morphometric and molecular differentiation of Pimelodus grosskopfii and Pimelodus yuma (Siluriformes: Pimelodidae)

Abstract Pimelodus grosskopfii and Pimelodus yuma, two species endemic to the Magdalena-Cauca basin in Colombia, overlap in the ranges of some of their diagnostic characters, which hampers their correct morphological identification. Aiming to help discriminate these species, this study conducted an integrative analysis using traditional and geometric morphometrics, phylogenetic analysis based on partial sequences of the mitochondrial cytochrome c oxidase subunit 1 gene (COI, cox1) and the identification of diagnostic Single Nucleotide Polymorphism markers (SNP). The species differ significantly in body geometry, allowing 100% discrimination, which was reinforced by a phylogenetic analysis that recovered well-supported monophyly of each species (posterior probability > 0.95). Additionally, the traditional morphometric results corroborated some previously reported diagnostic traits for both species and let us describe one non-overlapping ratio related to the adipose fin length. Three of five SNP markers had reciprocally exclusive alleles suitable for identifying each species. The morphometric and molecular methods conducted in this study constitute alternative tools for the correct discrimination of P. grosskopfii and P. yuma in the wild and in captive populations used for aquaculture.

摘要：哥伦比亚马格达莱纳-考卡流域（Magdalena-Cauca basin）特有两种油鲶属物种——格氏油鲶（Pimelodus grosskopfii）与尤马油鲶（Pimelodus yuma），二者部分鉴别特征的分布范围存在重叠，这对其准确形态鉴定造成了阻碍。为实现这两个物种的有效区分，本研究整合传统形态测量学与几何形态测量学（geometric morphometrics）方法开展分析，基于线粒体细胞色素c氧化酶亚基1基因（mitochondrial cytochrome c oxidase subunit 1，COI/cox1）的部分序列进行系统发育分析，并筛选诊断性单核苷酸多态性标记（Single Nucleotide Polymorphism，SNP）。研究结果显示，两种鱼类的躯体几何形态存在显著差异，可实现100%准确区分；系统发育分析进一步验证了这一结论，两个物种均形成了支持度极高的单系群（后验概率>0.95）。此外，传统形态测量学结果不仅证实了此前报道的两类物种的鉴别特征，还发现了一项与脂鳍长度相关的非重叠比例性状。5个SNP标记中有3个带有互斥等位基因，可用于两个物种的区分鉴定。本研究采用的形态测量学与分子生物学方法，可为野外种群及水产养殖圈养种群中的格氏油鲶与尤马油鲶的准确鉴别提供可行工具。