The origin of tiger salamander (Ambystoma tigrinum) populations in California, Oregon, and Nevada: introductions or relicts?

Abstract

Whether intentionally or accidentally introduced, exotic species have the capacity to dramatically disrupt native communities. In central California, tiger salamanders (Ambystoma tigrinum) have been introduced as a by-product of the sport fishing bait industry. Some of these introductions are relatively well known and have resulted in the formation of hybrids with the imperiled native California tiger salamander (A. californiense). Other populations of A. tigrinum, particularly in the northern and eastern parts of the state, remain poorly characterized and are present in regions where relictual amphibian populations of other species have persisted, suggesting that these might be relictual, native A. tigrinum. We used genetic sequence data to determine the provenance of all known extralimital A. tigrinum populations in California and adjacent Oregon and Nevada through comparison with reference samples from the native range of A. tigrinum. Our results suggest that A. tigrinum have been introduced in Northern California, Southern California and the Sierra Nevada, originating from multiple sources across the Great Plains of the US. Furthermore, two populations near the California-Oregon border are most closely related to A. tigrinum populations from Washington and Oregon and may represent native tiger salamander lineages.