A reappraisal of the California Roach/Hitch (Cypriniformes, Cyprinidae, Hesperoleucus/Lavinia) species complex.

Abstract

The California Roach (Hesperoleucus symmetricus) and Hitch (Lavinia exilicauda) form a species complex largely endemic to California (CA), USA. Using previous studies of this complex along with a recent comprehensive genomic analysis, we developed a highly supported taxonomic hierarchy of two genera, five species, four subspecies and multiple distinct population segments within two presently recognized species. The genera Lavinia and Hesperoleucus are supported as representing distinct lineages, despite occasional hybridization between them. While hybridization is one pathway to some speciation in this complex, hierarchical levels correlate nicely between genomic results and earlier morphological work. Hesperoleucus symmetricus is newly divided into four species (H. parvipinnis-Gualala Roach, H. mitrulus-Northern Roach, H. venustus-Coastal Roach, and H. symmetricus-California Roach) and two subspecies (H. s. serpentinus-Red Hills Roach, H. s. symmetricus-California Roach). Within H. venustus, two subspecies are identified (H. v. navarroensis-Northern Coastal Roach, and H. v. subditus-Southern Coastal Roach), which are supported by previous morphological studies but resolve discrepancies between those studies. Finally, six distinct population segments are identified within different species/subspecies: Kaweah, Russian River, Navarro River, Monterey, and Tomales Bay. Clear Lake Roach are introgressed between California and Coastal Roach, making them distinct but difficult to formally name. Results should greatly improve management and conservation of each taxonomic entity and help resolve past ambiguities. Additional studies are needed to improve range-wide boundaries and to investigate population structure within all species and subspecies identified in both Lavinia and Hesperoleucus lineages.