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Using ecological niche modeling to identify the potential range of novel invasive toadflax genotypes in the U.S. northern Rockies




McCartney, Kevin R., author
Ward, Sarah, advisor
Kumar, Sunil, committee member
Sing, Sharlene, committee member
Boone, Randall, committee member

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Dalmatian toadflax (Linaria dalmatica [L.] Mill.) and yellow toadflax (Linaria vulgaris Mill.) are vigorous invasive weeds posing significant management challenges. Predictions of suitable environments for these aggressive, emergent hybrid taxa are urgently required. Publishing predictive maps of the potential geographic distribution of toadflax will facilitate weed and land managers' efforts in maximizing limited resources for locating and controlling present and future populations of these invaders. The invaded ranges of Dalmatian and yellow toadflax span the Intermountain West, which encompasses the study area (i.e. Montana, Wyoming, and Colorado). These two species are listed as noxious weeds in all three states, with legal requirements for control in Wyoming and Colorado. Their hybrid progeny have even greater invasive potential; yet, relatively little is known about the current distribution of – and management approaches for – the hybrid. Ecological niche modeling with MaxEnt was performed for each taxon to identify favorable environmental characteristics and to predict fundamental niches in the study area. Areas at high risk of hybrid invasion were identified based on: a) known hybrid occurrence and associated environmental conditions; b) zones environmentally suitable for co-occurrence of the parental species; and c) areas common to both a) and b). Hybridization hot spots were predicted for western Montana; northwestern, northeastern, and southeastern Wyoming; and the Western Slope and Front Range of Colorado. Model output also indicated that hybrid toadflax would have greater ecological amplitude than its progenitors, with potential hybrid invasion in much of north central Montana where the parental species have not been reported. These methods for predicting the distribution of an emerging hybrid taxon with little occurrence data can be applied to similar taxa. Managers working to control the spread of toadflax can use these results to prioritize areas of high invasion risk. To solicit feedback from those involved with managing toadflax, seven people were interviewed regarding their level of knowledge of hybrid toadflax and the usability of the maps. There was a lack of awareness among interviewees regarding the potential geographic spread of the hybrid, and there were six requests for localized hot spot maps. By generating predictive maps of hybrid toadflax distribution and reaching out to weed and land managers, awareness of this taxon will increase and managers will be attentive to ongoing biocontrol and herbicide research.


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hybrid vigor
Linaria vulgaris
Linaria dalmatica


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