THE ROLE OF PARASITISM IN THE POPULATION-DYNAMICS OF THE BARK BEETLE PHLOEOTRIBUS SCARABAEOIDES (COL, SCOLYTIDAE) ON EUROPEAN OLIVES (OLEA-EUROPAEA)

Mortality from parasitism and intraspecific larval competition was mea sured on a spatial scale for the olive bark beetle, Phloeotribus scara baeoides, in cut logs within a Spanish olive orchard. Mortality due to parasitism was inversely density-dependent, whilst that due to compet ition was directly density-dependent. The consequences of these mortal ity effects of parasitoid and host population dynamics were investigat ed using a simple population model. In the absence of parasitism, the beetle population stabilized at around three reproducing females per 1 0 cm(2) of olive log surface. Using Roger's random parasite equation t o model the parasitoid-host interaction, the effects of parasitism wer e to destabilize an otherwise stable interaction. The limitations of t he model in its current from are discussed in detail. Suggestions are also made for future improvements to the model including the incorpora tion of spatial heterogeneity in parasitism.