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.

What can DNA tell us about biological invasions?

“…1). Moreover, at least 20 unique maternal lineages were identified in the introduced range (Johnson et al 2011). These genetic results are consistent with the reported introduction history, involving multiple releases of salamanders from Texas, Colorado, and New Mexico (Riley et al 2003).…”

“…1 Introduced tiger salamanders in California (samples represented by pie charts) show mitochondrial haplotypes from both the Southwestern (yellow) and Great Plains (orange) groups, consistent with multiple introductions from Colorado, New Mexico, and Texas (Riley et al 2003;Johnson et al 2011). Pacific Northwest (green), San Juan (gray), and Eastern (blue) groups are not represented in the introduced range samples (Johnson et al 2011).…”

“…If genetic variation is highly structured in the native range (i.e., high levels of among-population variation), then genotypes found in introduced populations might be assigned with high probability to geographic locations within the native range using clustering or assignment methods (Excoffier and Heckel 2006). For example, Johnson et al (2011) used mtDNA to show that introduced tiger salamanders (Ambystoma mavortium) in California originated from source populations in both the Great Plains and Southwest regions of North America, and not from the Pacific Northwest or east of the Mississippi River (Fig. 1).…”

Taxonomic Revision of Desmognathus wrighti (Caudata: Plethodontidae)

“…Range wide genetic analysis of N. lewisi and N. aff. lewisi will be necessary to test for a recent anthropogenic origin for the Hiwassee River population versus an ancient biogeographic connection to the Tar and Neuse (Johnson et al, 2011).…”

Origins of softshell turtles in Hawaii with implications for conservation

“…The application of molecular approaches to introduced populations can reveal hybridization and introgression (Holsbeek et al 2008, Parham et al 2013, Gering et al 2015, elucidate geographic origin (Jousson et al 2000, Johnson et al 2011, Siler et al 2014), infer population demography (Thibault et al 2009, Kalinowski et al 2010Purcell et al 2012), and elucidate the presence of cryptic species (May and Marsden 1992, Holland et al 2004, Stepien and Tumeo 2006. Genetic approaches are particularly helpful when unraveling introduction events that involve taxonomically problematic, sympatric and morphologically indistinguishable species, a situation particularly common to aquatic introductions (see Booth et al 2007 andGeller et al 2010 for recent reviews).…”