Abstract
Conservation of rare species requires careful consideration to both preserve locally adapted traits and maintain genetic diversity, as species’ ranges fluctuate in response to a changing climate and habitat loss. Salt marsh systems in California have been highly modified and many salt marsh obligate species have undergone range reductions and habitat loss with concomitant losses of genetic diversity and connectivity. Remaining salt marshes are threatened by rising sea levels, and so these habitats will likely require active restoration and re-establishment efforts. This study aims to provide a reference point for the current status of genetic diversity and range-wide population structure of a federally and state listed endangered plant, salt marsh bird’s-beak (Chloropyron maritimum subsp. maritimum) that can inform future preservation and restoration efforts. We used historical data and current monitoring information to locate and sample all known occurrences throughout the range of this subspecies in southern California, and three additional occurrences from Baja California, Mexico. We used flow cytometry and single nucleotide polymorphic markers (SNPs), generated by double-digest restriction-site associated DNA sequencing (ddRAD), to assess relative ploidy, and estimate genetic diversity and population structure across the region. Overall, we found five distinct genetic clusters that coincide with geographic regions. Genetic diversity was greatest in the southern part of the range including Baja California and San Diego. These findings can bolster management and restoration efforts by identifying potentially isolated occurrences and areas that are the richest sources of allelic diversity, and by providing insight into the amount of genetic differentiation across the taxon’s range.
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Acknowledgements
K. Preston, B. Richardson and three anonymous reviewers provided valuable comments that improved this manuscript. We thank B. Richardson, T. Tobiasson and A. Boyd for processing the flow cytometry data, and all land managers for site access. This research was supported by the San Diego Association of Governments, NAVFAC SW, the USGS Ecosystems Mission Area and Western Ecological Research Center, and used resources provided by the Core Science Analytics, Synthesis, & Libraries (CSASL) Advanced Research Computing (ARC) group at the USGS. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
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Milano, E.R., Mulligan, M.R., Rebman, J.P. et al. High-throughput sequencing reveals distinct regional genetic structure among remaining populations of an endangered salt marsh plant in California. Conserv Genet 21, 547–559 (2020). https://doi.org/10.1007/s10592-020-01269-3
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DOI: https://doi.org/10.1007/s10592-020-01269-3