Genomics reveals extensive population structure and undescribed phylogenetic relationships in the Cascade torrent salamander (Rhyacotriton cascadae)
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Abstract
Aim
Aims of the study are to examine patterns of range-wide genetic differentiation and population structure in a headwater obligate salamander living in a geologically rich region, to identify genetically distinct populations and areas of gene flow between them.
Location
Oregon and Washington in the Pacific Northwest, United States of America.
Time Period
Tissue samples were collected in 2022 and 2023.
Major Taxa Studied
The Cascade torrent salamander Rhyacotriton cascadae.
Methods
Utilisation of a genome-wide single nucleotide polymorphism (SNP) dataset from across the species range to conduct a principal components analysis (PCA), Bayesian model of population structure, co-ancestry matrix, phylogenetic tree and estimate genetic diversity.
Results
There are extensive levels of population structure within R. cascadae, including a previously unknown and highly differentiated clade. Structure is characterised by an island-like pattern wherein the species is comprised of six populations that function as independent demographic units, with gene flow largely constrained within populations.
Main Conclusions
Our findings reveal cryptic population structure within R. cascadae, identifying six distinct populations across the range. The northernmost population in the northwest of the species range in Washington is surprisingly highly divergent from the other five populations, and the divergence was not previously known to science. While major rivers act as phylogeographic boundaries between some populations, these boundaries appear to not always be complete.
Suggested Citation
Cousins, C.D., Olson, D.H., Millward, L.S., Adams, M.J., Pearl, C., Rowe, J., Garcia, T.S., 2026, Genomics reveals extensive population structure and undescribed phylogenetic relationships in the Cascade torrent salamander (Rhyacotriton cascadae): Journal of Biogeography, v. 53, no. 2, e70167, 15 p., https://doi.org/10.1111/jbi.70167.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Genomics reveals extensive population structure and undescribed phylogenetic relationships in the Cascade torrent salamander (Rhyacotriton cascadae) |
| Series title | Journal of Biogeography |
| DOI | 10.1111/jbi.70167 |
| Volume | 53 |
| Issue | 2 |
| Publication Date | February 17, 2026 |
| Year Published | 2026 |
| Language | English |
| Publisher | Wiley |
| Contributing office(s) | Forest and Rangeland Ecosystem Science Center |
| Description | e70167, 15 p. |
| Country | United States |
| State | Oregon, Washington |