Molecular Ecology (2007) 16, 4956-4971

Miki Okada, Riaz Ahmad and Marie Jasieniuk (2007)
Microsatellite variation points to local landscape plantings as sources of invasive pampas grass (Cortaderia selloana) in California
Molecular Ecology 16 (23), 4956-4971
Abstract: International trade in horticultural plants is a major pathway of introduction of invasive species. Pampas grass (Cortaderia selloana) is an invasive species of horticultural origin that is native to South America but cultivated as an ornamental in regions with Mediterranean climates worldwide. To gain insight into the introduction history of invasive populations in California, we analysed microsatellite marker variation in cultivated and invasive C. selloana. We sampled 275 cultivated plants from diverse sources and 698 invasive plants from 33 populations in four geographical regions of California. A model-based Bayesian clustering analysis identified seven distinct gene pools in cultivated C. selloana. Probabilities of assignment of invasive individuals to cultivated gene pools indicated that two gene pools accounted for the genomic origin of 78% of the invasive C. selloana sampled. Extensive admixture between cultivated source gene pools was detected within invasive individuals. Sources of admixed invasive individuals are probably landscape plantings. Consistent with the Bayesian assignment results indicating that multiple cultivated gene pools and landscape plantings are probable sources of invasive populations, F_ST and neighbour-joining clustering analyses indicated multiple escapes from shared sources in each geographical region. No isolation by distance or geographical trend in reduction of genetic diversity was evident. Furthermore, a generally random and discontinuous distribution of proportional assignments of invasive populations to cultivated gene pools suggests that introductions occurred recurrently within each geographical region. Our results strongly suggest that dispersal through local landscape plantings has contributed to the range expansion of invasive C. selloana in California.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Marie Jasieniuk

Research topic(s) for pests/diseases/weeds:
molecular biology - genes
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Cortaderia selloana (weed)		U.S.A. (SW)