title: Bridging factorial and gradient concepts of resource co-limitation: towards a general framework applied to consumers.
abstract: Organism growth can be limited either by a single resource or by multiple resources simultaneously (co-limitation). Efforts to characterise co-limitation have generated two influential approaches. One approach uses limitation scenarios of factorial growth assays to distinguish specific types of co-limitation; the other uses growth responses spanned over a continuous, multi-dimensional resource space to characterise different types of response surfaces. Both approaches have been useful in investigating particular aspects of co-limitation, but a synthesis is needed to stimulate development of this recent research area. We address this gap by integrating the two approaches, thereby presenting a more general framework of co-limitation. We found that various factorial (co-)limitation scenarios can emerge in different response surface types based on continuous availabilities of essential or substitutable resources. We tested our conceptual co-limitation framework on data sets of published and unpublished studies examining the limitation of two herbivorous consumers in a two-dimensional resource space. The experimental data corroborate the predictions, suggesting a general applicability of our co-limitation framework to generalist consumers and potentially also to other organisms. The presented framework might give insight into mechanisms that underlie co-limitation responses and thus can be a seminal starting point for evaluating co-limitation patterns in experiments and nature.
authors.affiliation: School of Biological Sciences and The Charles Perkins Centre, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: Erik
authors.initials: E
authors.lastname: Sperfeld
authors.affiliation: School of Biological Sciences and The Charles Perkins Centre, The University of Sydney, Sydney, NSW, 2006, Australia.|Faculty of Veterinary Science, The University of Sydney, Sydney, NSW, 2006, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Raubenheimer
authors.affiliation: Ecology and Ecosystem Modelling, Institute of Biochemistry and Biology, University of Potsdam, Am Neuen Palais 10, Potsdam, 14469, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Wacker
keywords: Consumer; essential nutrient; factorial design; food quality; growth rate; multi-nutrient limitation; nutritional ecology; performance landscape; substitutable resource; synergistic effect