Abstract
We experimentally investigate the effects of habitat connectivity on dynamics and rates of colonization and extinction in a model multitrophic system of a plant, a phytopathogen, a herbivorous insect, and its parasitoid. We hypothesize that pathogen and parasitoid in the model system are more sensitive to fragmentation than the herbivore and are more frequently absent from isolated patches, and investigate effects thereof on the underlying trophic level and stability of the system as a whole. specific attention will be paid tot he sensitivity of the pathogen to fragmentation. The results will be used to test the general hypothesis that as a result of habitat fragmentation and isolation the stability of multitrophic systems will decrease because i) within multitrophic systems there are differences in dispersal ability of the participants, ii) these differences can lead to local absence of the participants with the lowest dispersal capacity, iii) in turn this may lead to over-exploitation by species at a lower trophic level, and iv) these processes are enforced by habitat fragmentation and isolation. Specific hypotheses will be derived from project 1. In collaboration with projects 3 and 4, we will survey the presence of component species in other multitrophic systems in relation to different scales of habitat connectivity to arrive at greater generality of the results, especially for systems of interest from a conservation point of view.
Netherlands