Abstract Detail



Ecology

Sandacz, Daniel [1], Calkwood, John [2], Hakes, Alyssa [3].

Does the early bud escape the weevil? Examining the effects of microclimate and Pitcher's thistle phenology on weevil oviposition.

Wisconsin populations of the federally threatened Pitcher's thistle (Cirsium pitcheri) in Lake Michigan dune habitats are facing severe seed predation from an invasive weevil, Larinus planus. This weevil was originally implemented as a biocontrol agent for weedy thistles, however, it readily oviposits eggs into immature C. pitcheri flower heads where larvae will consume the developing seeds. Preliminary data from our experiments at Whitefish Dunes State Park (WDSP) show that C. pitcheri are more vulnerable to weevil damage at low dune elevations and when surrounded by marram grass neighbors. Another important factor to weevil oviposition choice is plant size (crown diameter); smaller C. pitcheri are more vulnerable to weevil infestation. Moreover, surface temperatures at grassy or sandy microsites near C. pitcheri stems at low and high elevations significantly differ from each other. In determining the maturity of flower heads, a greater proportion of flower heads are open at higher elevations, and larger plants are the first to open their flowers. Collectively, these data suggest that a plant's size and spatial location may influence its phenology. We are currently collecting additional data to determine 1) if microclimate differences cause variation in C. pitcheri flowering time, and 2) if flowering time affects weevil oviposition. We predict that a greater proportion of C. pictheri flowers will open earlier in microsites with a higher surface temperature, and that C. pictheri individuals that flower earlier will have fewer oviposition holes (i.e. escape weevils in time). This finding would suggest that variation in microclimate and phenology across the dune landscape may contrinute to the variation in weevil damage observed. Understanding the factors that predict weevil damage intensity is key to developing conservation strategies for this rare plant. 


1 - Lawrence University, Biology, 711 E. Boldt Way, Appleton, WI, 54911, United States
2 - Lawrence University, 711 E. Boldt Way, Appleton, WI, 54911, United States
3 - Lawrence University, Biology, 711 E. Boldt Way, Appleton, WI, 54911, USA

Keywords:
Cirsium pitcheri
Larinus planus
Dune habitat
phenology
Plant-Insect interaction
Conservation.

Presentation Type: Poster
Number: PEC016
Abstract ID:515
Candidate for Awards:Ecological Section Best Undergraduate Presentation Award


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