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Population genetics, demographic and evolutionary history of the Dudley’s lousewort (Pedicularis dudleyi), a rare redwood forest specialist


Pedicularis dudleyi (Dudley’s Lousewort, Orobanchaceae) is an extremely rare plant endemic to the redwood forests of Central California. Until recently, the species was known only from three extant natural populations. However, in 2019, one of those populations was described as a novel species (P. rigginsiae D.J. Keil) based on morphological and ecological data leaving only two populations described as P. dudleyi. While little is known about the past distribution of the species, historical records have led to speculation that the species was once more widespread and may have suffered from habitat destruction as a result of widespread logging during the early twentieth century. We utilized a combination of ddRAD SNP and Sanger sequencing data to: (1) Test the morphological hypothesis that P. rigginsiae is distinct from P. dudleyi; (2) Describe the genetic diversity and population structure of P. dudleyi and; (3) Test the hypothesis that the species underwent a bottleneck corresponding with increased logging of redwood forests in the early twentieth century. Our results support the recognition of P. rigginsiae as distinct from P. dudleyi, increasing the conservation priority of both species. Genetic diversity statistics and analyses of genetic structure suggest that both populations of P. dudleyi are highly differentiated from each other with one population exhibiting unexpected substructure. Finally, demographic modeling supports a scenario where the contemporary rarity of the species is explained by a recent bottleneck.

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We thank Abigail Moore and Leann Monaghan, Christine Edwards and two anonymous reviewers for their insightful comments on the manuscript. We also thank Lydia Smith, Austin Betancourt, Anjum Gujral, and Tracey Simmons for their invaluable assistance in the laboratory and field. The study benefited from the insights and logistics assistance of Portola Redwoods State Park staff Tyler Knapp, Ryan Diller, Tim Hyland and Joanne Kerbavaz. We are also grateful to Mujtaba Ghouse (Portola and Castle Rock Foundation) and Amy Patten (California Native Plant Society) for their valuable discussion and Kim Kuska, who shared many of his observations and insights with us. The computing for this project was performed at the OU Supercomputing Center for Education & Research (OSCER) at the University of Oklahoma (OU).


This study was funded through Research Grant #144 from Save the Redwoods League and the National Postdoctoral Research Fellowship in Biology Award #1810989.

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TMM, CH and BEC designed the study. TMM gathered and analyzed the data and wrote the manuscript. CH and BEC provided guidance on the study and commented on all drafts of the manuscript.

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Correspondence to Tracy M. Misiewicz.

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The authors have no conflict of interest.

Data availability

Raw sequence data were deposited at the National Center for Biotechnology Information Short Read Archive ( database under the accession number BioProject ID PRJNA742774. Processed SNP data (vcf, genepop, STRUCTURE and DIYABC-RF formats) and the concatenated ITS and matK-5’trnK intron sequence alignment are available from DataDryad ( Genbank accession numbers for the ITS and matK-5’trnK intron are listed in Table 1.

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Misiewicz, T.M., Hauser, C. & Carter, B.E. Population genetics, demographic and evolutionary history of the Dudley’s lousewort (Pedicularis dudleyi), a rare redwood forest specialist. Conserv Genet 23, 513–525 (2022).

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  • Pedicularis dudleyi
  • Rare plants
  • Redwood specialist
  • ddRAD seq
  • Bottleneck
  • Demographic history