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Phylogeography of Camassia quamash in western North America: postglacial colonization and transport by indigenous peoples


  • This research was conducted when H. Tomimatsu was a postdoctoral research fellow at the University of British Columbia. His research has focused mainly on the dynamics of plant populations and communities in human-modified landscapes. S. Kephart is a Professor of Biology at Willamette University, where she conducts research on diverse questions related to hybridization, plant-pollinator interactions, systematics and conservation biology. M. Vellend is an Assistant Professor and Canada Research Chair in Conservation Biology at the University of British Columbia, where he conducts research on the ecology, genetics and conservation of plant populations and communities.

Hiroshi Tomimatsu, Fax: +81 229 84 6490; E-mail: Current address: Graduate School of Life Sciences, Tohoku University, Osaki, Miyagi 989-6711, Japan


Recent human activities have spread numerous plant species across the globe, yet it is unclear to what degree historical human activities influenced plant dispersal. In western North America, Camassia quamash was one of the most important food plants for indigenous peoples, who transported its propagules either intentionally or accidentally. We investigated how human and natural dispersal might have contributed to the current pattern of spatial genetic structure in C. quamash by performing phylogeographical surveys at two geographical scales. We sequenced two noncoding regions of chloroplast deoxyribonucleic acid (DNA) in 226 individuals from 53 populations of C. quamash as well as 126 individuals from 21 populations of the non-food plant Zigadenus venenosus. Contrary to the expectation of anthropogenic transport, C. quamash populations did not exhibit weaker genetic structure than Z. venenosus populations. We also failed to find convincing evidence for signatures of transport. Instead, our data showed strong effects of past glaciation and geographical barriers of the mountains in the Cascade Range, Olympic Peninsula and Vancouver Island. West of the Cascades, the species appears to have largely migrated northward from a southern refugium after deglaciation, whereas few populations having a highly divergent haplotype might have survived in southwestern Washington. Our data suggest that despite substantial ethnobotanical evidence for anthropogenic transport, the current pattern of genetic structure of C. quamash does not show any detectable signatures of transport by indigenous peoples and is better understood as the result of natural dispersal processes.

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