United States Department of Transportation
i
Landscape Genomics Study on California Tiger Salamander
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2020-07-01
[PDF-6.03 MB]
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Edition:Final Report,
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Abstract:The California Tiger Salamander – Ambystoma californiense (CTS) is endemic to California. The Sonoma County distinct population segments (DPS) and Santa Barbara County DPS are federally listed as Endangered, while the Central California DPS is federally listed as Threatened. CTS is listed as Threatened under the California Endangered Species Act. Caltrans is required to consult with regulatory agencies about the impacts of transportation projects. A major conservation issue for CTS is the ongoing hybridization with the introduced non-native barred tiger salamander - Ambystoma mavortium (BTS). The two species hybridized in the areas where they came into contact creating admixed populations around the introduction sites and generating hybrid swarms. Thus, CTS recovery, in part, depends on preventing the geographical spread of introgression. Landscape genomics is at the leading edge of new genetic tools that provide fine scale, spatially explicit data allowing researchers and managers to achieve a deeper understanding of how different habitat types impede or enhance the resistance to movement of organisms on landscapes. This work constituted the first such genomic data set explicitly designed to quantify the effects of roads on gene movement in an endangered species. The most fundamental result of this study howed that, as originally predicted, roads appear to have a larger measurable effect on the movement of hybrid salamanders than on pure natives. Several possible mechanisms, detailed fully in the final report, may be responsible for this pattern, and they cannot be disentangled without explicit experiments that are beyond the scope of this project. However, it does appear that roads are a potent barrier to the movement of hybrid salamanders, and as such should be considered when planning for the movement of non-native genes in the future.
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