HYBRIDIZATION AND CRYPTIC SPECIES IN DICAMPTODON (CAUDATA: DICAMPTODONTIDAE).

The salamander genus Dicamptodon consists of at least four genetically divergent groups of populations with 10-19 fixed allelic differences (out of 31 loci scored) between populations in alternative groups. One of these groups corresponds to D. copei; the other three until now usually have been considered to belong to the single morphologically homogeneous species D. ensatus. Two instances of geographic contact between genetic units occur in the genus, one between D. copei and "D. ensatus" in northern Oregon and the other between two highly divergent types of "D. ensatus" in coastal northern Calfornia. In the former case no hybridization occurs, while in the latter a narrow hybrid zone has been observed. There appears to be selection against hybrids within this hybrid zone, and introgression beyond the zone is apparently nonexistent. The population groups therefore appear to be genetically independent units, and Dicamptodon is best considered to consist of four species: D. copei, D. ensatus, D. tenebrosus, and D. aterrimus.