Non-host neighbors provide associational susceptibility of a native thistle to an invasive weevil
Results/Conclusions: There was a significant difference in the frequency of oviposition holes among treatments; 44% of C. pitcheri located at low elevations with grass neighbors had oviposition holes present, whereas the frequency of oviposition holes was lower for plants at the same elevation with grass neighbors (9%) and for plants at higher elevations (15%). This difference in damage among treatments was also significant at the season’s end. C. pitcheri in the low-elevation grass treatment had on average twice as many flower heads damaged than those in the low-elevation clipped treatment. There was not a significant difference in seed predation between the low-elevation clipped treatment and high elevation grass treatment. Together these results suggest that L. planus weevils prefer to disperse at low dune elevations and through the dominant Ammophila grass matrix to locate and climb onto its host. C. pitcheri that germinate further away from beach grass may have a better chance of successfully reproducing. I discuss the mechanisms that may explain why a non-host grass provides associational susceptibility to an invasive herbivore’s unintended host.