Print PageAn important recent advance in food web ecology has been the application of theory regarding spatial gradients to studies of the factors that affect animal population dynamic. Here, we compare the importance of local versus geographic controls on arthropod communities, using Spartina alterniflora and associated arthropods as a model system in controlled greenhouse mesocosms. Building on extensive studies of the S. alterniflora food web at the local scale, we hypothesize that geographic variation in S. alterniflora quality is an important bottom-up control on food web structure, and that geographic variation in S. alterniflora quality will interact with the presence of predators and top omnivores to strongly mediate herbivore densities.
Results/Conclusions
In this experiment, bottom-up sources of variation in plant quality strongly determined food web structure in the Spartina mesocosms. However – this pattern was driven by local nutrient variability rather than by latitudinal variation in plant quality exhibited across large latitudinal scales. Top down effects on consumers were driven by the omnivore in our study rather than the strictly carnivorous mesopredator. In those cases where predators did exert a significant suppressing effect on herbivores, that impact was itself mediated by host-plant characteristics. Plants set the stage on which herbivorous insects and their enemies interact.
