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Abstract Detail


Hakes, Alyssa [1], Paniagua-Montoya, Monica [1], Czaplinska, Tina [1].

Bad neighbors and evil weevils: why the surrounding neighborhood of Picther's thistle (Cirsium pitcheri) may influence its damage levels.

Pitcher's thistle (Cirsium pitcheri), is a federally-threatened native plant that is endemic to western Great Lakes dune habitats. The invasion of a seed-eating Larinus weevil poses an emrging threat to the rare thistle's continued persistence. Our previous research on this system shows that the presence of marram grass (Ammophila breviligulata) neighbors increases the likelihood of weevil damage to Pitcher's thistle, but it is unclear why weevils prefer to be near grasses, especially since it is not a suitable host. We conducted mark-and-recapture experiments to test the hypothesis that grasses were aiding weevil dispersal (dispersal-mediated effects). In addition, we examined whether grass neighbors may be altering the abiotic conditions surrounding thistles in a way that is preferrable to them (refuge-mediated effects). We collected weevils on site, marked them, and released each individual 0.5 m away from a C. pitcheri target plant. We noted the time weevils spent resting, walking, or flying and whether these behaviors were taking place on the sand, on debris, or on grass. Of the 170 weevils that we observed, 44% (75) reached the target host. Four weevils died while struggling on the hot sand, and the remaining weevils flew out of sight (long-distance dispersal event). Of the weevils that reached the target thistle, 85% of them utilized grass neighbors in their dispersal (either climbing onto the thistle directly from the grass, or by flying from grass to thistle). The remaining weevils walked or flew onto the thistle from the sand. Weevils spent significantly more time on grass neighbors than on the sand or other types of substrate. In addition, surface temperature was significantly cooler near grass-surrounded thistles than near sand-surrounded thistles. There was a significant positive relationship between temperature and the likelihood of weevil dispersal away from the target thistle. Results from our study suggest that grasses may benefit weevil dispersal and influence host plant selection, resulting in grass-surrounded thistles experiencing greater levels of damage. Our experiment has implications for C. pitcheri conservation and we have identified locations within the dunes with greater risk to weevil damage.

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1 - Lawrence University, Biology, 711 E. Boldt Way, Appleton, WI, 54911, USA

Neighbor effects
Plant-Insect interaction
Biocontrol impacts
Cirsium pitcheri
Larinus weevil.

Presentation Type: Poster
Session: P, Ecology
Location: Grand Ballroom - Exhibit Hall/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 5:30 PM This poster will be presented at 6:15 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PEC010
Abstract ID:269
Candidate for Awards:None

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