G. de Jong

Acquisition and Allocation of Resources: Their Influence on Variation in Life History Tactics

Attempts to demonstrate trade-offs between alternative life history tactics have been relatively successful at higher taxonomic levels, but often fail at the level of individuals within a population. In this note we propose a simple model that explains this failure. The aim of our model is to understand the observations of positive correlations between life history traits where trade-offs, and hence negative correlations, are expected. It is assumed that the amount of resources that individuals can spend on life history traits varies between individuals. When some individuals spend much on several life history traits and others spend little, positive correlations are observed. Whether the observed correlations between life history traits are negative or positive depends on the relative variation in the acquisition and the variation in the allocation of resources.

Contribution of genetics to the study of animal personalities: a review of case studies

Summary The need for evolutionary studies on quantitative traits that integrate genetics is increasing. Studies on consistent individual differences in behavioural traits provide a good opportunity to do controlled experiments on the genetic mechanisms underlying the variation and covariation in complex behavioural traits. In this review we will highlight the contribution of genetic studies in animal personality research. We will start with reviewing the evidence that shows how much variation in animal personality traits is genetic, and connect this to knowledge from human personality studies. We will continue by considering the nature of that variation, its generation and maintenance. Finally we will point to further possibilities for studying the genetics of animal personalities. We will underline the importance of integrating both proximate and ultimate approaches when studying the evolution of animal personalities.

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.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 alloc...

Additive and nonadditive genetic variation in avian personality traits

Individuals of all vertebrate species differ consistently in their reactions to mildly stressful challenges. These typical reactions, described as personalities or coping strategies, have a clear genetic basis, but the structure of their inheritance in natural populations is almost unknown. We carried out a quantitative genetic analysis of two personality traits (exploration and boldness) and the combination of these two traits (early exploratory behaviour). This study was carried out on the lines resulting from a two-directional artificial selection experiment on early exploratory behaviour (EEB) of great tits (Parus major) originating from a wild population. In analyses using the original lines, reciprocal F1 and reciprocal first backcross generations, additive, dominance, maternal effects ands sex-dependent expression of exploration, boldness and EEB were estimated. Both additive and dominant genetic effects were important determinants of phenotypic variation in exploratory behaviour and boldness. However, no sex-dependent expression was observed in either of these personality traits. These results are discussed with respect to the maintenance of genetic variation in personality traits, and the expected genetic structure of other behavioural and life history traits in general.

Sex ratio under the haystack model: Polymorphism may occur

The haystack model describes a population which is subdivided in local mating groups. Female-biased sex ratios are known to occur under these circumstances. Analysis of this model, assuming that the sex ratio is under control of one gene with two alleles, acting in the mother, shows that a monomorphic evolutionary stable strategy (ESS) does not always exist, and that polymorphism can then be expected. In most cases this is caused by an effect of the gene action of alleles: no sex ratio exists capable of withstanding the invasion of rare “mutant” alleles of all possible degrees of dominance. A genetic analysis leads to different conclusions than a phenotypic analysis.

Phenotypic plasticity in morphological traits in two populations of Drosophila melanogaster

Isofemale lines of two populations of Drosophila melanogaster, originating from France and Tanzania, were examined over a range of temperatures. Morphological traits showed distinct patterns in phenotypic plasticity; flies of the two populations differed in shape.