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 格氏油鲶（Pimelodus grosskopfii）与尤马油鲶（Pimelodus yuma）为哥伦比亚马格达莱纳-考卡河流域特有物种，二者的部分鉴别特征取值范围存在重叠，这对其准确的形态学鉴定造成了阻碍。为助力这两个物种的区分鉴定，本研究整合运用传统形态测量学（traditional morphometrics）与几何形态测量学（geometric morphometrics）方法、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）部分序列开展系统发育分析，并筛选诊断性单核苷酸多态性（Single Nucleotide Polymorphism, SNP）标记。研究结果显示，两种鱼类在躯体几何形态上存在显著差异，可实现100%准确区分；系统发育分析进一步验证了该结果，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，传统形态测量学的分析结果不仅佐证了此前报道的两种鱼类的部分鉴别性状，还新发现了一项与脂鳍长度相关的非重叠比例特征。5个SNP标记中有3个携带互斥等位基因，可用于分别鉴定两个物种。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所用的人工繁育种群中格氏油鲶与尤马油鲶的准确鉴别提供可靠辅助工具。