Trophic ecology

Modelling nutritional ecology

Researchers: Jerome Buhl, Fiona Clissold, Mathieu Lihoreau, Stephen Simpson

The aim of this research is to develop a generic modelling framework for nutritional ecology, linking the nutritional biology of individual organisms to population- and community- level processes across multiple scales and within an evolutionary context. Using agent-based models, we simulate the physiology, the behaviour, and the fitness of individuals evolving in spatially and nutritionally explicit environments. The models can be parameterised to represent a specific type of organism and generate testable ecological hypothesis, where theoretical and experimental approaches are tightly combined in a constant dialogue. This approach will allow us tackling key ecological questions from a phenotypic, population, and community perspective. Which foraging strategy to evolve in a given environment? To what extent can meta-population dynamics be explained by nutritionally motivated movements? How do ecosystems resilient to disturbances emerge?

Key Publications:

  • Simpson SJ, Raubenheimer D, Charleston MA, Clissold FJ, and the ARC-NZ Vegetation Function Network Herbivory Working Group. 2010. Modelling nutritional interactions: from individuals to communities. Trends in Ecology and Evolution 25:53-60.
  • Kearney M, Simpson SJ, Raubenheimer D, and Helmuth B. 2010. Modelling the ecological niche from functional traits. Philosophical Transactions of the Royal Society B 365:3469-3483.
  • Reynolds AM, Sword GA, Simpson SJ, and Reynolds DR. 2009. Predator percolation, insect outbreaks and phase polyphenism. Current Biology 19:20-24.

Plant-herbivore interactions

Researchers: Ximonie Clark, Fiona Clissold, James Gilbert, Stephen Simpson

Interactions between plants and their herbivores sit at the nexus of all food webs, and how well an animal matches its demand for nutrients with supply from the environment affects not only that individual, but has population- and community-level consequences. To understand trophic interactions within food webs, we need to be able to predict the nutritional consequences for a herbivore of ingesting a particular plant; however, grinding up plant tissues and measuring their chemical composition does not provide an indication of the ‘quality’ of that plant to herbivores. The ability of an insect herbivore that chews plant leaves to absorb nutrients depends on how these nutrients have been ‘packaged’ within the plant interacting with the insect’s morphological tools (typically the mandibles and gastrointestinal tract), and its behavioural and physiological flexibility. By utilizing a combination of laboratory and field studies, we aim to understand the interactive effects of plant traits (i.e., primary and secondary metabolites and biomechanical properties), animal traits (i.e., morphology, physiology and behaviour) and abiotic conditions influence diet selection in herbivores, the consequences of such choices for the herbivore and how this affects population and community outcomes.

Key Publications:

  • Clissold FJ, Tedder BJ, Conigrave AD, and Simpson SJ. 2010. The gastrointestinal tract as a nutrient-balancing organ. Proceedings of the Royal Society B 277:1751-1759.
  • Clissold FJ, Sanson GD, Read J, and Simpson SJ. 2009. Gross vs. net income: How plant toughness affects performance of an insect herbivore. Ecology 90:3393-3405.
  • Raubenheimer D, and Simpson SJ. 2009. Nutritional PharmEcology: Doses, nutrients, toxins, and medicines. Integrative and Comparative Biology 49:329-337.
  • Clissold FJ. 2007. The Biomechanics of chewing and plant fracture: Mechanisms and implications. Advances in Insect Physiology 34:317-372.

Carnivory: from Physiology to Communities

Researchers: Shawn Wilder, Stephen Simpson

The complexity of many natural food webs makes them daunting to study empirically. However, a nutritional approach may aid in decomposing food webs into more manageable units and understanding the mechanisms that influence how community members interact with one another. Carnivores can have large impacts on the structure and functioning of communities and ecosystems through their direct and indirect effects on other animals. Our research is guided by the premise that animals have specific physiological requirements for nutrients and will modify their foraging behavior to meet those requirements, which can have consequences for community and ecosystem dynamics (e.g., degree of omnivory, food chain length, nutrient cycling). We are particularly interested in understanding how trophic level (i.e., herbivore vs. carnivore) influences diet regulation rules, responses to food containing particular macronutrient combinations and the relative availability of key nutrients in nature. Currently, we are examining variation in the nutrient content of insects at different trophic levels in a phylogenetically-diverse data set and the implication of this variation for carnivores (e.g., growth, reproduction, diet selection) and, ultimately, community dynamics (e.g., omnivory, intraguild predation and food chain length).

Key Publications:

  • Jensen K, Mayntz D, Toft S, Raubenheimer D, and Simpson SJ. 2011. Nutrient regulation in a predator, the wolf spider Pardosa prativaga. Animal Behaviour 81:993-999.
  • Hewson-Hughes AK, Hewson-Hughes VL, Miller AT, Hall SR, Simpson SJ, and Raubenheimer D. 2011. Geometric analysis of macronutrient selection in the adult domestic cat, Felis catus. Journal of Experimental Biology 214:1039-1051.
  • Wilder SM, and Eubanks MD. 2010. Might nitrogen limitation promote omnivory among carnivorous arthropods: Comment. Ecology 91:3114-3117.
  • Raubenheimer D, Simpson SJ, and Mayntz D. 2009. Nutrition, ecology and nutritional ecology: toward an integrated framework. Functional Ecology 23:4-16.
  • Mayntz D, Raubenheimer D, Salomon M, Toft S, and Simpson SJ. 2005. Nutrient-specific foraging in invertebrate predators. Science, 307:111-113.