The demography of native and non-native plant species in mountain systems: examples in the Greater Yellowstone Ecosystem

In mountainous areas, native and non-native plants will be exposed to climate change and increased disturbance in the future. Non-native plants may be more successful than natives in disturbed areas and thus be able to respond quicker to shifting climatic zones. In 2009, monitoring plots were established for populations of a non-native species (Linaria dalmatica) and a closely related native species (Castilleja miniata) on an elevation gradient in the Greater Yellowstone Ecosystem, USA. Population data were collected twice during the growing season for 3 years and used to calculate population vital rates for both species, and to construct population dynamics models for L. dalmatica. Linaria dalmatica vital rates were more associated with climatic/environmental factors than those of C. miniata. Population dynamics models for L. dalmatica showed no trend in population growth rate (λ) vs. elevation. The highest λ corresponded with the lowest vegetation and litter cover, and the highest bare ground cover. All populations with λ < 1 corresponded with the lowest measured winter minimum temperature. There was a negative association between λ and number of weeks of adequate soil moisture, and a weak positive association between λ and mean winter minimum temperature. Variance in vital rates and λ of L. dalmatica suggest broad adaptation within its current range, with the potential to spread further with or without future changes in climate. There is evidence that λ is negatively affected by persistent soil moisture which promotes the growth of other plant species, suggesting that it might expand further if other species were removed by disturbance.