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International Journal of Plant Sciences








Premise of research. Population connectivity, the exchange of genes among geographically separated subpopulations, is thought to be a key process for the maintenance of genetic diversity and the survival of invasive species in newly colonized areas. Plant populations' degree of genetic connectivity, which occurs via pollen and seed dispersal, leads to different degrees of genetic admixture and genetic structure. Environmental barriers and differential selection pressures that are variable across time and space tend to alter genetic structure within and among populations via restriction or facilitation of gene flow. Canada thistle, an invasive species of the United States and Canada, is well known for production of high numbers of seeds, asexual reproduction, and wide environmental tolerance. These factors may influence its success as an invader by facilitating population persistence.

Methodology. In this study we evaluated genetic connectivity of 12 Canada thistle populations across a 75-km area using 10 microsatellite loci, estimated the spatial scale of genetic exchange between populations, and tested for an association between genetic structure and variation in landscape characteristics.

Pivotal results. All loci were highly polymorphic within populations, and populations were significantly differentiated from one another ( FST = 0.21 , p = 0.001), but environmental, geographic, and climatic factors were found to have little explanatory power for the observed genetic structure. Bayesian clustering analysis suggested the presence of two distinct genetic groups and admixture in several populations.

Conclusions. We conclude that, for this species, genetic admixture and co-occurrence of genetically distinct types may play an important role in rapid adjustment to diverse environments and persistence of populations across the landscape.


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Original Publication Citation

Nobarinezhad, M. H., Challagundla, L., & Wallace, L. E. (2020). Small-scale population connectivity and genetic structure in Canada Thistle (Cirsium arvense). International Journal of Plant Sciences, 181(4), 473-484. doi:10.1086/706882


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