Document Type : Agricultural Entomology
Authors
1 Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran
2 Plant Protection Research Department, Tehran Agricultural and Natural Resources Research and Education Center, AREEO, Varamin, Iran
Abstract
Ooencyrtus telenomicida Vassiliev and Ooencyrtus fecundus Ferrier & Voegele (Hymenoptera, Encyrtidae) are egg parasitoids of Eurygaster integriceps Puton (Hemiptera: Scutelleridae). These species are sympatric and have widely overlapping niches, hence competitive displacement of one by another species is expected. However, in natural habitats, they coexist peacefully and no one is replaced by another. Therefore, they need some ways to avoid ecological exclusion. In this study, direct competition between larvae was investigated. In the first experiment, multiparasitism was studied by simultaneous release of equal number of the two species at different densities of both parasitoid and host. In the second experiment, sequential release of an inexperienced female of the two species with different time intervals from 3 h to 10 d was investigated. A telytokous population of O. fecundus was encountered. The multiparasitism experiment in 3h to 10 d intervals showed a 2.35-fold advantage of O. telenomicida over O. fecundus. A relative increase in parasitism rate of the second invader was observed in 2 to 7 d intervals. The simultaneous parasitism by the two species showed a 3-fold advantage of O. telenomicida in lower densities, which it enhanced to 15-fold at higher parasitoid densities. Results of this study revealed advantage of bisexual population of O. telenomicida over telytokous O. fecundus, which in higher densities it may also lead to exclusion of the latter, although such densities on host clutches are seldom expected in nature. Moreover, the results of competition of the two bisexual populations is still unknown and may be different.
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