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1 October 2006 The status of Impatiens capensis (Balsaminaceae) on the Pacific Northwest coast
Peter F. Zika
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Three Pacific Northwest taxa, Impatiens aurella, Impatiens ecalcarata, and Impatiens noli-tangere, are considered native plants, based on collecting histories beginning in the 1850s. Impatiens capensis, indigenous to eastern North America, is found in coastal Oregon, Washington, and British Columbia, where it was first collected in 1950. Its late arrival suggests Impatiens capensis is a recent introduction and not native, contrary to reports in regional floras. Rapid dispersal and population increases have made it common on many shorelines. Of 39 indigenous Impatiens ecalcarata populations located west of the Cascade Mountains, 34 (87%) were mixed with introduced Impatiens capensis. Spontaneous hybrids flowered simultaneously with both parents. In a mixed population pollinators favored the flowers of Impatiens capensis (77% of 295 visits) over hybrids (18%) and Impatiens ecalcarata (4%). Hybrids were frequent, ranging from 6–69% of the individuals present, and were found in all mixed populations of Impatiens capensis and Impatiens ecalcarata. Impatiens capensis and its hybrids together comprised more than half the individuals present at most sites, suggesting Impatiens capensis is a potential threat to the genetic integrity of native coastal populations of the relatively uncommon Impatiens ecalcarata.

Peter F. Zika "The status of Impatiens capensis (Balsaminaceae) on the Pacific Northwest coast," The Journal of the Torrey Botanical Society 133(4), 593-600, (1 October 2006).[593:TSOICB]2.0.CO;2
Received: 12 December 2005; Published: 1 October 2006

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