Spotted knapweed (Centaurea stoebe) east of Missoula, Montana. Photo courtesy of Norman E. Rees, USDA Agricultural Research Service, Bugwood.org
Title: Knapweed Project
Students: Alexey Shipunov [Postdoctoral Research Associate now at the Woods Hole Oceanographic Institution], Anil Raghavendra [PhD candidate]
Summer Intern: Maryse Crawford
Collaborators: Dr. Cort Anderson, Dr. Timothey Prather, Dr. Sanford Eigenbrode, Dr. Mark Schwarzlaender, Dr. Ray Callaway
Department: Forest Resources
Invasiveness may be the result of ‘novel weapons’ that aid an introduced plant to outcompete evolutionarily naïve neighbours in its new range. Roots of Eurasian species of Centaurea are thought to produce allelochemicals that function as novel weapons in North America. However, a series of three experiments suggested that fungal endophytes that naturally established in seedling roots could have been confounded with novel weapons. In the first two experiments, endophtyes in roots of C. stoebe significantly reduced the biomass of naïve neighbours (i.e., Festuca idahoensis plants), compared to the effect of endophyte-free C. stoebe on F. idahoensis. For the third experiment, relative abundances of endophytes of C. stoebe in both its native and invaded ranges were determined so that representatives of the six most common haplotypes, three from each range, could be employed as root inoculants. In general, each of these endophytes again reduced the growth of naïve neighbours (i.e., Festuca idahoensis); remarkably, each also increased the growth of adapted neighbours (i.e., Festuca ovina) that were tested for the first time. Four of the six endophytes caused C. stoebe to gain a competitive advantage over its naïve neighbour that was significantly greater than the competitive advantage of endophyte-free C. stoebe over that same neighbour. Endophyte-free C. stoebe had no greater competitive advantage over F. idahoensis than it had over F. ovina. By aiding an invasive plant against F. idahoensis in a cryptic manner, endophytes could be confounded with novel weapons. However, without evidence that these endophytes are themselves native to Eurasia, it is premature to assert that they are themselves novel weapons.
For more information, email the PI: Dr. George Newcombe