Nuclear and mitochondrial diversification in two native California minnows: insights into taxonomic identity and regional phylogeography

摘要

Diversification of the California icthyofauna has been greatly influenced by a complex geomorphological history and past fluctuations in climate regimes. This complex history has resulted in areas of high endemism for a number of taxa. Here we present data on the two species in the genus Lavinia, the California roach (Lavinia symmetricus) and hitch (Lavinia exilicauda), that are widespread throughout the region. Individuals were sequenced at two mitochondrial DNA fragments and genotyped at eight microsatellite loci. Mitochondrial DNA indicated the presence to two highly divergent clades representing roach from the Gualala and Pit Rivers, which diverged from all other Lavinia ～3-6 MYA. Support was also found for roach from the Navarro River, Tomales Bay region, the Red Hills region, and the Russian River-Clear Lake basin. We found no evidence for any geographical groupings of mtDNA haplotypes for roach and hitch from the Monterey Bay region and the Sacramento-San Joaquin River drainages. Additionally roach and hitch from these two areas could not be readily distinguished by mtDNA data. Analysis of microsatellite DNA recovered all groupings found in the mtDNA analysis and was able to separate out roach, hitch, and all currently recognized subspecies of each species. These results indicate that hybridization may obscure the phylogenetic/phylogeographic informativeness of mtDNA in this group. Additionally, these results suggest that differentiation in this group occurs at the river basin level and that the described genetic entities constitute distinct units and should be conserved as such.