Eurytoma serratulae and E. robusta (Hymenoptera, Eurytomidae): complementary host exploitation strategies of coexisting parasitoids and their impact on the host Urophora cardui

By

Zwölfer, Helmut
Böheim, Marc
Beck, Erwin, 1937-

Type

Article

Date of Publication

2015

Original Publication

Journal of Hymenoptera research

Volume

42

Pages

47-62

Subjects

coexistence of Eurytoma , parasitoid-interactions , stimulation of gall growth , Urophora cardui galls

Contributed by

Pensoft Publishers

Language

English

Published by

Washington, D.C International Society of Hymenopterists

Identifiers

DOI: https://doi.org/10.3897/JHR.42.8847

 

Abstract

Our study investigates the host exploitation strategies of Eurytoma serratulae and E. robusta (Chalcidoidea, Eurytomidae), two parasitoid species that co-occur in gall populations of the tephritid Urophora cardui on Cirsium spp. The endoparasitoid E. serratulae detects the host larvae before an externally visible gall is formed. It profits from large galls, as its parasitization rate increases with increasing numbers of chambers per gall. Oviposition by the ectoparasitoid E. robusta does not occur until a distinct gall with chambers has been formed. Its parasitization rate reaches highest values in medium-sized galls. Eurytoma robusta is the dominant parasitoid in host populations with low and moderate gall densities, whereas E. serratulae is the superior exploiter of host populations with high gall densities. Within single galls E. robusta is an important hyperparasitoid of E. serratulae, but E. serratulae has no adverse influence on E. robusta. Parasitism by E. serratulae induces host larvae to promote gall growth, an effect that is profitable to both the parasitoid and the remaining host larvae in the gall. Parasitism by E. robusta often leads to smaller galls, as cases of unsuccessful parasitization result in empty gall cells.