UC Davis

Lampreys on the West Coast of North America are an understudied group of native fishes. Many West Coast lamprey populations are in decline, but the lack of historical data and poor fundamental scientific understanding of these fishes obstruct conservation efforts. Taxonomic uncertainty is prevalent across the entire lamprey lineage, in part due to patterns of life history variation (i.e. migration, parasitism) and associated morphological diversity (i.e. body size, oral disc dentition). In some cases, different life history variants are accurately classified as distinct species, but in other cases, these life history variants co-occur within the same species. As genetic tools were developed, some taxonomic uncertainty has been resolved; however, previous research has been limited to few genetic markers and included few samples from California. This study utilizes mitochondrial phylogenetics and molecular species delimitation methods in tandem with phylogenomics and population genomic analyses to investigate species diversity, evolutionary relationships, and genomic diversity of lampreys in California (Entosphenus spp. and Occidentis spp.). Study results show relatively shallow divergences between Entosphenus species, deep divergences between Occidentis species, and high species richness in Occidentis in California, including two novel species found in the Napa River and Alameda Creek. In Entosphenus, results largely support current taxonomy, except the unnamed Goose Lake lamprey, which is not genetically distinct from E. lethophagus. Genomic differentiation across E. tridentatus individuals is isolated to a putative chromosomal inversion region, which is associated with variation in reproductive maturity timing. Study results advance our understanding of lampreys and inform conservation management.