ACQUISITION AND ALLOCATION OF RESOURCES - GENETIC (CO)VARIANCES, SELECTION, AND LIFE HISTORIES

We investigate a genetic model in which two traits result from the acquisition and allocation of a single resource. Phenotypic values for the two traits are written as a product of the total amount of the resource acquired and the proportion allotted to each of them. Although multiplicative gene action determines the traits, the epistasis at the gene level is mainly expressed in the additive genetic variance and covariance at the level of the measured traits. Phenotypic and additive genetic covariances between the two traits can be positive or negative; a negative additive genetic covariance can be accompanied by a positive phenotypic covariance. An acquisition-allocation model is the only model of multiplicative gene action that allows simultaneous selection on two traits to be written in matrix form. We use the model of resource acquisition and allocation to find the life-history consequences of acquisition of a resource and allocation to two traits. Two alternative allocation strategies-priority allocation to viability or to fecundity-lead to different evolutionarily stable strategies (ESSs) in life-history components. Primary allocation to fecundity has allocation fractions of zero or one as its stable state. Primary allocation to viability leads to an ESS allocation fraction that depends on resource availability, population growth rate. and the age structure of the population. In a poor environment and for inherently long-lived animals, the ESS allocation fraction tends in the direction of higher viability.