Individual Energetics and the Equilibrium Demography of Structured Populations

Abstract

This paper considers the relationship between the demographic mechanisms of population control and the energetics of the individuals who comprise the population. We examine the equilibrium properties of a class of structured population models in which individuals compete for some environmental resource (such as food) and demonstrate that population demography is independent of the nature of the feedback loop which establishes the equilibrium state. We thus derive general insights into the influence exerted by individual energetic and allocation strategies on population average demographic characteristics. We show that models of individual energetics which produce apparently very similar predictions at the individual level can result in very different behaviour at the population level. In addition, we observe that different models of individual mortality can imply marked differences in population demography and that the common assumption of constant mortality can be responsible for potentially unrealistic model behaviour. Our results emphasise the substantial data requirements for parameterising and testing individual-based models.

Limits to the potential distribution of light brown apple moth in Arizona–California based on climate suitability and host plant availability

“…This approach requires considerably more weather data to drive the model, which increases biological realism and captures important Fig. 6 The added indirect effects of rainfall on LBAM distribution: a the simulated average distribution of yellow starthistle in California (see Gutierrez et al 2005), b the distribution of average total rainfall greater than 350 mm at elevations below 1,000 m, c superimposing total rainfall [350 mm on the simulated distribution and abundance of LBAM based only on temperature Potential distribution of light brown apple moth 3327 temporal factors that affect the distribution and abundance of a species (e.g., Gutierrez et al 1994;Gurney et al 1996;Gutierrez 1996;Holst and Ruggle 1997;Rochat and Gutierrez 2001;Baumgärtner 1984, 2007). The developmental biology of LBAM is relatively simple; it lacks an overwintering diapause, it is polyphagous, and its populations are suppressed by a combination of dispersal mortality, extremes of temperature, host plant availability, and in Australia, by native natural enemies that operate in a density independent manner (Danthanarayana and colleagues).…”

A regional analysis of weather mediated competition between a parasitoid and a coccinellid predator of oleander scale

“…Hughes & Gilbert 1968, Gilbert & Gutierrez 1973, and the use of physiologically based models has further simplifi es the problem (e.g. Gutierrez & Wang 1977, Gutierrez & Baumgärtner 1984, Gurney et al 1996, Gutierrez 1996, Holst et al 1997, Gutierrez et al 2005. Physiologically based demographic models describe basic biological processes of per capita poikilotherm growth and reproduction as driven by weather and as modifi ed by resource density and competition (i.e.…”

Bioenergetics, overcompensation, and the source–sink status of marine reserves

“…Two major types of energy allocation models have been proposed, which are referred to as net-production allocation and grossproduction allocation (Gurney et al 1996;Nisbet et al 2004). The rate of net production per unit of biomass equals the difference between the energy intake rate and the loss rate due to maintenance, sj(R) -m, whereas gross production equals sj(R).…”

“…The distinction between the two classes is that reproduction is supposed to be proportional to the energy intake rate either before or after maintenance costs have been substracted. By consequence, the allocation models assume different behaviour at low food conditions: in the gross-production model, individuals reproduce as long as the food concentration is positive, whereas in the net-production model, there is a threshold food concentration below which individuals stop reproducing (Gurney et al 1996). Simple MPA models formulated in terms of ordinary or partial differential equations (ODEs or PDEs, respectively) are often based on LotkaVolterra type models (Neubert 2003;Steele and Beet 2003;Baskett et al 2006), without explicitly considering bioenergetics.…”

“…In the context of size-structured population models, Gurney et al (1996) have shown that the individual-level energetics influence by which demographic process populations are regulated (i.e., reproduction, maturation, or survival limitation). The relevance of such individual-level assumptions in the context of MPAs is their implications for the local ecological response to the presence or absence of harvesting (aspect (i) above); the food web response will depend on how individuals react to (changes in) their environment.…”