Centaurea solstitialis was introduced to the United States from Europe during the 19th century and since has wreaked havoc on the native plant communities and rangelands. Interestingly, Centaurea calcitrapa and Centaurea sulphurea, two plant species that are phylogenetically similar to C. solstitiallis, were introduced to the U.S. at about the same time and established viable populations, but have not become invasive in North America. Furthermore, C. calcitrapa is far more abundant in its native range of Spain than C. solsitialis. We compared characteristics of seeds and seedlings produced from seeds collected from a number of populations in the native and non-native ranges for each species.  We tested the hypothesis that C. soltitialis would demonstrate greater plasticity or evidence for greater evolutionary change than the two exotic but non-invasive congeners.

Results/Conclusions

Seeds and seedlings of all three species showed significant differences in morphology between populations from native and non-native ranges. However, the differences between Spanish and North American populations of C. solstitialis were substantially greater than differences between populations of C. sulphurea or C. calcitrapa. Thus C. solstitialis appeared to have undergone more evolutionary change than C. sulphurea or C. calcitrapa. Greater ability of C. solstitialis to acclimate or adapt to new environments may be a major driver of the species’ success in non-native ranges.