From Physiology to Population Dynamics and Communities

Abstract

Levels of organization provide one of the central themes around which biologists attempt to understand the living world. Mechanistic explanations for behaviour at one level tend to be couched in terms of behaviour of lower level systems; the hierarchy is familiar, running from cell biology and biochemistry, to physiology, individual behaviour, population dynamics, communities, and ultimately ecosystems and the biosphere. Generally the most useful explanations link adjacent steps in the hierarchy. Here, I explore a very small part of what physiology can tell us about populations and communities of animals, concentrating on drawing attention to promising lines for further research. Schoener (1986) and Kingsolver (1989) adopt a similar approach but cover very different aspects of the same general problem. My specific aim is to show how simple, tactical models of energy acquisition and use by individual animals generate understanding of both population dynamics and species' distributions. The principle concern of the paper is with the rules determining rates of energy assimilation, respiration and production by individual animals. In broad terms, the physiology of resource acquisition and use provides the scaling rules within which populations and communities must operate (Peters, 1983, 1986). This paper focuses upon metabolic rate, particularly maintenance metabolism and the partitioning of assimilated energy between metabolism and production. It then links these processes to single-species population dynamics, as well as to predator-prey and competitive interactions, and goes on to explore in a very tentative manner the size of species' geographic ranges, and questions of tropical and temperate species' diversity.