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Rogy, Pierre

University of British Columbia

Food webs, networks of feeding interactions within ecological systems, have presented a consistent challenge to generations of researchers. Nonetheless, some recent approaches, in particular those focussing on energy and matter flows, have a strong potential to move the field forward. This dissertation focuses on integrating two of these approaches: ecological stoichiometry and energy channel theory. The former focuses on the role of elemental ratios in shaping feeding interactions, while the latter focuses on describing food webs in terms of different chains, or channels, with organisms interacting more strongly within than across channels. In the integrated framework, ecological stoichiometry will provide a mechanism to explain the emergence of energy channels, while energy channels theory will scale ecological stoichiometry to entire communities. I tested predictions derived from the framework using the aquatic food webs of epiphytic tank bromeliads through a combination of complementary approaches. First, I conducted two greenhouse experiments, where I examined how the stoichiometry of a resource, light exposure, and either the bromeliad itself or a macroscopic consumer acted together to influence energy flows in the microscopic compartments of the bromeliad food web. The experiments showed that bromeliads compete more strongly with algae than bacteria, and emphasised the important role of consumer recycling in contexts of nutrient limitation. Second, I conducted two field experiments, where I manipulated the stoichiometry of a resource and the presence of a top predator, studying how these treatments altered energy flow in model food webs. Here, the working hypotheses were challenged by nutrient co-limitation and underlined the importance of consumer recycling. Finally, using the database constructed by the Bromeliad Working Group, I examined how the stoichiometry of organisms influenced the flows of energy in the food webs that they compose. This chapter showed that, although important in shaping energy flows, ecological stoichiometry alone is not sufficient to fully describe them. This dissertation has two main take-home messages: first that ecological stoichiometry theory and energy channel theory can be successfully integrated in a single theoretical framework, and second that the multi-faceted nature of food webs begets an array of complementary theories to be comprehensively studied.

Text

2024-07-11

Attribution-NonCommercial 4.0 International

http://hdl.handle.net/2429/88622

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc/4.0/