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Boneset and gall midges

Blair Qi and Emily Vincent
Ecology class, BIO 342, Biology Department, DePauw University
Fall semester 2014

Tall boneset, Eupatorium altissimum, is host to a species of gall-forming midge.  The midge lays its eggs in the plant’s tissue and induces the plant to form a gall.  Tall boneset spreads vegetatively through underground rhizomes.  All plants in one patch may be genetically identical.  We compared the size of galls within genetically identical patches of tall boneset. 

We hypothesized that galls would be similar in size when they grow on tall boneset plants in genetically identical patches.  We also hypothesized that galls would be larger when midges lay eggs on genetically weaker plants.

We measured plant height and gall size at five sites in the Nature Park.

Plant height varied significantly among the five sites (p < 0.001).  Plants were taller at sites A, B, C, and D and were shorter at site E.  There was no correlation between plant height and gall volume, but taller plants had lower gall positions.