PARENT SESSION
Oral Session #46: Animal Community Ecology: Pools, Foodwebs, Structure. Presiding: D. Post.
Wednesday, August 8, 2001. 8:00 AM to 12:00 PM. Hall of Ideas I.
Temporally variable trophic flows across habitats and the indirect effects.
Takimoto, Gaku1, Iwata, Tomoya1, Murakami, Masashi2, 1 2
ABSTRACT- There is increasing attention directed to the importance of trophic flows across habitats. When a habitat receives allochthonous resource inputs, apparent competition between allochthonous and in situ resources could be induced. Alternatively, in situ resource could be released from predation pressure if consumer shifts its diet to allochthonous resource. Therefore, indirect effects of allochthonous resource inputs on in situ resource could be either positive or negative. In this study, I investigate how temporal variability of resource flows (constant, seasonal, or pulsed flows) determines the indirect effects. For example, marine-derived resource is constantly transported to barren islands surrounded by always-productive ocean. In contrast, at interface between temperate stream and riparian forest, reciprocal resource flows alternate due to seasonal difference in productivity between aquatic and terrestrial systems. I incorporate these features of allochthonous resource input into a model of consumer-resource interaction. Other features of the model are an explicit parameterization of the time scale of the consumer relative to the resource dynamics, and consumer's type II functional response. Numerical analysis of the model reveals that, with constant resource inputs or fast consumer dynamics, indirect effect of allochthonous resource is negative, whereas seasonal or pulsed inputs, together with slow consumer dynamics, result in positive indirect effect. The results illustrate that the temporal as well as the spatial dynamics of trophic flows needs to be grasped to assess the effects across habitats.
KEY WORDS: allochthonous resource, indirect effects, temporal variability, apparent competition