PARENT SESSION
Tuesday, August 8, 8:00-11:30 am
COS 20 - Food webs I: trophic interactions
Mississippi, Mezzanine Level, Cook Convention Center
Presiders: D Gruner

Processing chain facilitation in a grassland detrital foodweb: the interaction between Porcellio scaber, a common macrodetritivore on soil nematodes.

Bastow, Justin^*,1, ¹ University of California, Davis, Davis, CA

ABSTRACT- Detritus and carrion often support successions of consumers, whose interactions may be structured by changes in the condition of their shared resource. One model of such species interactions is a processing chain, in which consumers feeding on the resource in a less processed state change the resource condition for subsequent consumers. I tested the hypothesis that a common macrodetritivore, Porcellio scaber, interacted with soil fauna through the processing of plant litter in microcosm experiments. I added different detrital resources to soil from a California coastal prairie in order to simulate different levels of detritus processing by the macrodetritivore. Microcosms which received only whole grass litter corresponded to detrital foodwebs lacking macrodetritivores, while microcosms which received mixtures of Porcellio scaber feces and grass litter corresponded to different levels of litter processing by Porcellio scaber. Litter processing by Porcellio scaber increased bactivorous nematodes by 97% in 30 days. Fungivorous nematodes showed much weaker responses to litter processing, suggesting that Porcellio scaber primarily facilitates the bacterial channel of the soil foodweb. Microcosms which received fragmented grass litter were not significantly different from microcosms which received unprocessed (whole) grass litter. This suggests that Porcellio scaber's facilitation of bactiviorous nematodes is not the result of comminution, but some other change in detritus quality.

Key words: species interactions, community ecology, soil foodwebs