First DNA Barcode Reference Library for the Identification of South American Freshwater Fish from the Lower Paraná River

Valid fish species identification is essential for biodiversity conservation and fisheries management. Here, we provide a sequence reference library based on mitochondrial cytochrome c oxidase subunit I for a valid identification of 79 freshwater fish species from the Lower Paraná River. Neighbour-joining analysis based on K2P genetic distances formed non-overlapping clusters for almost all species with a ≥99% bootstrap support each. Identification was successful for 97.8% of species as the minimum genetic distance to the nearest neighbour exceeded the maximum intraspecific distance in all these cases. A barcoding gap of 2.5% was apparent for the whole data set with the exception of four cases. Within-species distances ranged from 0.00% to 7.59%, while interspecific distances varied between 4.06% and 19.98%, without considering Odontesthes species with a minimum genetic distance of 0%. Sequence library validation was performed by applying BOLDs BIN analysis tool, Poisson Tree Processes model and Automatic Barcode Gap Discovery, along with a reliable taxonomic assignment by experts. Exhaustive revision of vouchers was performed when a conflicting assignment was detected after sequence analysis and BIN discordance evaluation. Thus, the sequence library presented here can be confidently used as a benchmark for identification of half of the fish species recorded for the Lower Paraná River.鱼类物种的准确鉴定对于生物多样性保护与渔业管理至关重要。本研究基于线粒体细胞色素c氧化酶亚基I（mitochondrial cytochrome c oxidase subunit I）构建序列参考文库，以实现对巴拉那河下游79种淡水鱼类的准确鉴定。基于K2P遗传距离的邻接法（Neighbour-joining）分析结果显示，几乎所有物种均形成了互不重叠的聚类簇，且每个聚类的自展支持率均≥99%。97.8%的物种可实现成功鉴定，此类物种与其最近邻物种的最小遗传距离均大于其自身的最大种内遗传距离。整个数据集存在2.5%的条形码间隙（barcoding gap），仅存在4个例外情况。种内遗传距离范围为0.00%至7.59%，种间遗传距离范围为4.06%至19.98%；本研究未纳入最小遗传距离为0%的Odontesthes属（Odontesthes）物种。本研究通过BOLD的BIN分析工具、泊松树过程模型（Poisson Tree Processes）以及自动条形码间隙发现工具（Automatic Barcode Gap Discovery）完成序列文库验证，并结合专家开展可靠的分类学赋值。当序列分析与BIN不一致性评估发现分类学赋值存在冲突时，研究人员对标本凭证进行了全面复核。综上，本研究构建的序列文库可作为可靠基准，用于鉴定巴拉那河下游已记录鱼类物种中的半数物种。