Abstract 42
Eitam, A., Pavlíček, T., Blaustein, L. and Nevo, E. 2002: Effect of inter- and intra-slope contrasts at "Evolution Canyon", Israel, on a gall aphid and its natural enemies. J. Med. Ecol. 3: 47-52.
We use the aphid Aploneura lentisci as a model to test the hypothesis that abiotic stress is the dominant factor shaping ecological contrasts between and within the slopes of 'Evolution Canyon', Mt. Carmel, Israel. Aploneura lentisci forms galls on Pistacia lentiscus, one of only a few woody plant species common to both slopes. Gall densities were nearly ten–fold greater on the hotter, drier south-facing slope (SFS), but there were no statistically significant intra-slope differences in gall abundance. The large inter-slope difference is consistent with the hypothesis that there is an indirect effect of abioticstress on A. lentisci, i.e., that P. lentiscus is less resistant to the aphid on the more stressful SFS. However, the most likely explanation is the greater abundance on the SFS of both primary and secondary hosts (P. lentiscus and roots of grasses,respectively). No statistically significant inter- or intra-slope differences in gall size or in abundance of parasitoids and predators were observed, except for a decrease in the abundance of parasitoids with elevation on the SFS. The latter is consistent with a direct negative effect of abiotic stress, which is greatest on the higher elevations of this slope.




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