Landscape genomics of the streamside salamander: Implications for species management in the face of environmental change

Understanding spatial patterns of genetic differentiation and local
adaptation is critical in a period of rapid environmental change. Climate
change and anthropogenic development have led to population declines and
shifting geographic distributions in numerous species. The streamside
salamander, Ambystoma barbouri, is an endemic amphibian with a small
geographic range that predominantly inhabits small, ephemeral streams. As
A. barbouri is listed as near-threatened by the IUCN, we describe
range-wide patterns of genetic differentiation and adaptation to assess
the species’ potential to respond to environmental change. We use outlier
scans and genetic-environment association analyses to identify genomic
variation putatively underlying local adaptation across the species’
geographic range. We find evidence for adaptation with a polygenic
architecture and a set of candidate SNPs that identify genes putatively
contributing to local adaptation. Our results build on earlier work that
suggests that some A. barbouri populations are locally adapted despite
evidence for asymmetric gene flow between the range core and periphery.
Taken together, the body of work describing the evolutionary genetics of
range limits in A. barbouri suggest that the species may be unlikely to
respond naturally to environmental challenges through a range shift or in
situ adaptation. We suggest that management efforts such as assisted
migration may be necessary in the future.