14 - An adaptive resource ecology : foundation and prospects

Summary

In this concluding chapter, I review retrospectively the conceptual foundation established by preceding sections, and outline prospects for further developments of the resource-centred metaphysiological approach. I also look beyond the specific models developed for large mammalian herbivores in this book, to raise some general theoretical issues concerning the dynamics of consumer–resource systems. Thereby I introduce the vision of a broader Adaptive Resource Ecology.

Retrospective review

In starting this book, I set out to establish a conceptual framework for modelling herbivore–vegetation systems that would accommodate spatiotemporal variability in the resource base. The approach entailed integrating models of adaptive resource use by individual herbivores into a metaphysiological formulation of population dynamics. The basic principle was not to develop an elaborate, multi-level simulation, but rather to incorporate the functional outcome of lower-level processes, such as adaptive behaviour, into higher-level dynamics.

The starting foundation was Caughley's (1976a) modification of the classical Lotka–Volterra equations for herbivore–vegetation systems. I extended Caughley's analysis by recognizing how variation in food quality could cause the consumer gain function to deviate from the intake (‘functional’) response to changing resource abundance. Furthermore, I specified mortality losses as being non-linearly dependent on nutritional gains (following Getz 1991, 1993). In addition, I allowed for physiological expenditures as an independent biomass loss. The GMM label captured mnemonically the basic processes governing consumer biomass dynamics, at all levels from individuals to populations: Growth, Metabolism and Mortality.