Document Type


Publication Date


Publication Title

Ecological Applications


Hybridization and introgression between introduced and native salmonids threaten the continued persistence of many inland cutthroat trout species. Environmental models have been developed to predict the spread of introgression, but few studies have assessed the role of propagule pressure. We used an extensive set of fish stocking records and geographic information system (GIS) data to produce a spatially explicit index of potential propagule pressure exerted by introduced rainbow trout in the Upper Kootenay River, British Columbia, Canada. We then used logistic regression and the information-theoretic approach to test the ability of a set of environmental and spatial variables to predict the level of introgression between native westslope cutthroat trout and introduced rainbow trout. Introgression was assessed using between four and seven co-dominant, diagnostic nuclear markers at 45 sites in 31 different streams. The best model for predicting introgression included our GIS propagule pressure index and an environmental variable that accounted for the biogeoclimatic zone of the site (r2¼0.62). This model was 1.4 times more likely to explain introgression than the next-best model, which consisted of only the propagule pressure index variable. We created a composite model based on the model-averaged results of the seven top models that included environmental, spatial, and propagule pressure variables. The propagule pressure index had the highest importance weight (0.995) of all variables tested and was negatively related to sites with no introgression. This study used an index of propagule pressure and demonstrated that propagule pressure had the greatest influence on the level of introgression between a native and introduced trout in a human-induced hybrid zone.


Ecological Applications, 20(1), 2010, pp. 263–277 ©2010 by the Ecological Society of America

"Permission to make digital or hard copies of part or all of articles published in journals of the Ecological Society of America for personal use or educational use within one's home institution is granted without fee, provided that the first page or initial screen of a display includes the notice "Copyright by the Ecological Society of America," along with the full citation, including the name of the author(s). Copyrights for components of a work owned by others than ESA must be honored. Authors may post their articles to their personal or home institution’s website or institutional repository and may make and distribute photocopies of such articles."