Expanding the Distribution and Phylogenetic Insights ofChrysobrycon mojicaiin the Peruvian Amazon: Morphological and Molecular Analyses with Taxonomic Corrections

Abstract

AbstractThis study focuses on the genusChrysobrycon, particularlyChrysobrycon mojicai, which was initially described in the Amacayacu National Natural Park in Colombia. Here, we document a new geographical record ofC. mojicaiin various locations of the Peruvian Amazon, including the Nanay, Putumayo, Tapiche, and Tigre Rivers basins. Based on morphological, morphometric, and molecular analyses, we confirm the presence ofC. mojicaiin these new locations, expanding its known distribution. Morphological features such as the distinct shape of the hypertrophied scales and the specific arrangement of teeth were used to confirm its identity. Molecular data, obtained through cytochrome oxidase I (COI) gene sequencing, provide additional validation and contribute to understanding its phylogenetic relationships within the Stevardiini tribe. Our phylogenetic analysis reveals unresolved relationships within the tribe, particularly in the genusGephyrocharax, and highlights discrepancies in the current taxonomic framework, withC. mojicaishowing close genetic affinity toC. myersifrom the Pachitea River basin. The study also presents morphometric information of the holotype of C. mojicai, specifically the percentages of measurements relative to the head, which were not included in the original description. It also includes ecological observations of the habitats whereC. mojicaiwas collected, noting its presence in blackwater and mixed water streams characterized by fluctuating water levels and specific physical and chemical parameters. Additionally, the study restricts the distribution ofC. guahibofor Colombia and invalidates the COI sequence ofHysteronotus megalostomusavailable in molecular databases. This research not only expands the known distribution ofC. mojicaibut also underscores the need for further taxonomic and ecological studies to resolve existing ambiguities within the Stevardiini subfamily.