Parasitic relationships between a gall-forming insect Tomoplagia rudolphi (Diptera: Tephritidae) and its host plant (Vernonia polyanthes, Asteraceae)

We studied the impact caused by Tomoplagia rudolphi Lutz & Costa Lima (Diptera: Tephritidae) on the architecture, flower production, seed germination and seed viability of its host plant Vernonia polyanthes Less (Asteraceae). We measured the gall influence on the number df lateral shoots, on the production of Rower heads and on seed viability. Gall formation induced a significant increase in the number of lateral shoots modifying the host plant normal growth pattern. Galled stems produced an average of 7.3 +/- 0.45 shoots, whereas ungalled stems produced 5.6 +/- 0.60 shoots. Galling also caused a significant reduction in seed viability. Seeds of galled stems had a total percent seed germination mean of 28.4%, while seeds of ungalled stems had a mean of 33.8 %. However, flower head production and seed germination velocity were not affected by the gall. This study showed that T. rudolphi galls influence the architecture and seed viability of its host plant. (C) 1996 Annals of Botany Company