Vol. 51 No. 2, 2012

Changes in Oak Gall Wasps Species Diversity (Hymenoptera:Cynipidae) in Relation to the Presence of Oak Powdery Mildew (Erysiphe alphitoides)

Mohammed Reza Zargaran^1,*, Nadir Erbilgin², and Youbert Ghosta¹

¹Plant Protection Department- Sero Road- Agricultural Faculty, Urmia Univ., PO Box 165, Urmia, Iran
²4-42 Earth Sciences Building, Department of Renewable Resources, Univ. of Alberta, Edmonton T6G 2E3, AB Canada

Mohammed Reza Zargaran, Nadir Erbilgin, and Youbert Ghosta (2012) Plant-mediated interactions usually lead to multipartite interactions in a community of organisms. To evaluate the impact of oak powdery mildew Erysiphe alphitoides infestation on the distributions of cynipid oak gall wasps (Hymenoptera: Cynipidae), a field survey was conducted in West Azerbaijan Province, Iran, in 2 consecutive years of 2009-2010. Multiple samples were taken from both infected and uninfected trees (Quercus spp.) at 4 different sites where maximum activity of E. alphitoides occurred and cynipid galls exhibited complete development. The species diversity and richness of gall-forming wasps were estimated and also parameters such as Simpson’s index, Shannon’s H’, and the Sorensen similarity quotient were calculated. Data were also analyzed by independent-samples t-test to compare the mean numbers of galls occurring on infected and uninfected trees. Results clearly indicated that the highest richness and diversity of oak gall-forming wasps were consistently found on uninfected trees at all study sites in the 2 consecutive years. Further, the number and diversity of gall-forming wasps were negatively correlated with the extent (percentage) of pathogen infection, and trees with the heaviest E. alphitoides infection had the lowest numbers of gall-forming wasps. In addition, E. alphitoides decreased the rate of Sorensen’s coefficient between regions where oak trees infected with E. alphitoides were sampled. This study demonstrates plant-mediated interactions between a native pathogen and a community of gall-forming insects on oak trees.

Key words: Cynipid gall wasps, Tree-mediated interactions, Species diversity, Abundance, Oak forest.

*Correspondence: E-mail:Zargaran391@yahoo.com