Barriers to gene flow in Embiotoca jacksoni, a marine fish lacking a pelagic larval stage

Abstract.— Marine species generally show high dispersal capabilities, which should be accompanied by high levels of gene flow and low speciation rates. However, studies that focused on the relationship between dispersal and gene flow in marine fishes have been inconclusive. This study focuses on the black surfperch, Embiotoca jacksoni , a temperate reef fish that lacks a pelagic larval stage and lives on almost continuous reefs along the California and Baja California coasts. Mitochondrial control-region sequences from 240 individuals were obtained, and phylogeographic patterns were analyzed. A major phylogeographic break was found at Santa Monica Bay, a sandy expanse that prevents adult dispersal. Deep water separating the southern California Channel Islands was also found to be a major barrier to gene flow. Minor phylogeographic breaks were also detected in the Big Sur/Morro Bay and in the Punta Eugenia/Guerrero Negro regions, but none in the Point Conception region. Gene flow levels in E. jacksoni were found to be almost identical to those of another species with limited dispersal, Acanthochromis polyacanthus , thus indicating that the lack of a pelagic larval stage combined with barriers to adult dispersal may have had similar effects on these two species.