From organism to population: the role of life-history theory

The role of life-history theory in population and evolutionary analyses is outlined. In both cases general life histories can be analysed, but simpler life histories need fewer parameters for their description. The simplest case, of semelparous (breed-once-then-die) organisms, needs only three parameters: somatic growth rate, mortality rate and fecundity. This case is analysed in detail. If fecundity is fixed, population growth rate can be calculated direct from mortality rate and somatic growth rate, and isoclines on which population growth rate is constant can be drawn in a ”state space” with axes for mortality rate and somatic growth rate. In this space density-dependence is likely to result in a population trajectory from low density, when mortality rate is low and somatic growth rate is high and the population increases (positive population growth rate) to high density, after which the process reverses to return to low density. Possible effects of pollution on this system are discussed. The state-space approach allows direct population analysis of the twin effects of pollution and density on population growth rate. Evolutionary analysis uses related methods to identify likely evolutionary outcomes when an organism's genetic options are subject to trade-offs. The trade-off considered here is between somatic growth rate and mortality rate. Such a trade-off could arise because of an energy allocation trade-off if resources spent on personal defence (reducing mortality rate) are not available for somatic growth rate. The evolutionary implications of pollution acting on such a trade-off are outlined

Loss Aversion, Price and Quality

The Spence model (1975) is extended so that customers’ utility depends on their disposition to the firm in addition to quantity and quality of the good consumed. Disposition is determined by customers’ perception of firm’s pricing and quality decisions, which perception is ‘reference dependent’. The profit maximising and efficient price and quality combinations are derived. Adjustment to a change in economic conditions may call for price rigidity, quality rigidity or both depending on the level of the reference price and qualityLoss Aversion, monopoly pricing, quality

An Integrated Approach to Teaching Price Discrimination

Textbooks present the three 'degrees' of price discrimination as a sequence of independent pricing methods and consequently provide inadequate insight as to when a firm might adopt a particular pricing strategy. The paper describes a taxonomy of the various mechanisms of price discrimination, which can be used to teach monopolistic price discrimination in an integrated way. The pricing strategy adopted by firms is based on (i) the information on consumer demand available to it and (ii) whether the firm has the ability to conduct non-linear pricing. The paper proposes a method for ranking profit and efficiency levels under different price discrimination strategies. The proposed taxonomy is compared to the existing textbook approach.

Bringing Competition to Urban Water Supply

This paper proposes a market-based reform that would introduce competition into the provision of urban water. This proposal calls for a decoupling of infrastructure control and ownership of water whereby the property rights to water would be transferred to private hands. The proposal involves periodically allocation (e.g. by auction) of existing water stock held in urban catchments to virtual suppliers who then compete in providing bulk water. This change when coupled with effective third party access and retail competition would lead to a competitive market for the provision of urban water. The approach aims to address concerns over inefficient pricing and infrastructure provision under the current arrangement.Water Utilities, Efficient Water Pricing, Water Provider Competition

Multiple environmental controls explain global patterns in soil animal communities

Soil animals play important roles in ecosystem functioning and stability, but the environmental controls on their communities are not fully understood. In this study, we compiled a dataset of soil animal communities for which the abundance and body mass of multiple soil animal groups were recorded. The mass–abundance scaling relationships were then used to investigate multiple environmental controls on soil animal community composition. The data reveal latitudinal shifts from high abundances of small soil animals at high latitudes to greater relative abundances of large soil animals at low latitudes. A hierarchical linear mixed effects model was applied to reveal the environmental variables shaping these latitudinal trends. The final hierarchical model identified mean annual temperature, soil pH and soil organic carbon content as key environmental controls explaining global mass–abundance scaling relationships in soil animal communities (R2c = 0.828, Ngroup = 117). Such relationships between soil biota with climate and edaphic conditions have been previously identified for soil microbial, but not soil animal, communities at a global scale. More comprehensive global soil community datasets are needed to better understand the generality of these relationships over a broader range of global ecosystems and soil animal groups