Tritrophic interactions between cereals, aphids and parasitoids: Discrimination of different plant-host complexes by Aphidius rhopalosiphi (Hymenoptera: Aphidiidae)

Abstract

Abstract. The tritrophic interactions between two different plant-host complexes, Avena sativa-Sitobion avenae, Triticum aestivum-S. avenae and the aphid parasitoid Aphidius rhopalosiphi were studied with respect to odour learning and recognition by the parasitoid. The orientation behaviour of females towards odours from either uninfested or aphid-infested oat or wheat plants was tested in a series of dual choice Y-tube olfactometer experiments. Female parasitoids had the opportunity to gain a single oviposition experience on either the oat-S. avenae or wheat-S. avenae complex before the experiment. In the first set of experiments, where A. rhopalosiphi was reared on the oat-S. avenae complex, eight odour-bait combinations were tested. The females did not discriminate between uninfested oat and wheat. After oat complex experience, females responded to odours from the oat complex, but not to odours from the wheat complex. Consequently, in a direct comparison the oat complex was preferred over the wheat complex. After wheat complex experience, the parasitoid's orientation responses gave a different picture. Both, the wheat complex and the oat com plex, were then shown to be equally attractive. Hence, in direct comparison no preference was recorded between the oat and wheat complexes. In a second set of experiments, where A. rhopalosiphi was reared on the wheat-S. avenae complex, a possible influence of any pre-adult or emergence-related host plant experience could be excluded as the same results were obtained as before. At first glance the responses towards the different odour baits seem inconsistent. However, the results may be explained using a simple model with two key odour components.

Permutation tests for analyzing cospeciation in multiple phylogenies: applications in tri-trophic ecology

“…Evolutionary histories can be shared by more than two trophic levels, (Ahmad, Aslam, and Razaq, 2004;Forister and Feldman, 2010;Micha, Kistenmacher, Mölck, and Wyss, 2000), which is referred to as a phylogenetic cascade by Forister and Feldman (2010). We have demonstrated in this paper that the relationship among three phylogenies can be closely examined by using permutation of the individual tree tip labels and test statistics based on dominant eigenvalues and partial correlations.…”

Aphid-deprivation from Brassica plants results in increased isothiocyanate release and parasitoid attraction

“…This period in the diel rhythm of the wasps corresponds to the time window when adult female wasps show increased locomotor activity (M. Friedli and A. NajarRodriguez, personal observations). Providing parasitoids with a positive experience that is associated with an odour can facilitate the effective use of volatile chemicals by parasitoids, or enhance their ability to respond to these odours, thus increasing foraging efficiency (Grasswitz and Paine 1993;Micha et al 2000). Thus, newly emerged female wasps were exposed to Brassica leaves infested with B. brassicae aphids upon emergence.…”

Estimating ecotoxicological effects of pesticide drift on nontarget arthropods in field hedgerows

“…T. pyri is a generalist phytoseiid that feeds on spider mites, insects, and pollen [33,34], and its abundance is likely to be higher in the hedgerow. A. rhopalosiphi is instead a specialist parasitoid, and its abundance should be linked to that of its prey [35]. The population response during or soon after the treatments would also be of interest, but specific studies are needed [36].…”