Lee Alan Dugatkin

Beyond the prisoner's dilemma: Toward models to discriminate among mechanisms of cooperation in nature

The iterated prisoners dilemma game, or IPD, has now established itself as the orthodox paradigm for theoretical investigations of the evolution of cooperation; but its scope is restricted to reciprocity, which is only one of three categories of cooperation among unrelated individuals. Even within that category, a cooperative encounter has in general three phases, and the IPD has nothing to say about two of them. To distinguish among mechanisms of cooperation in nature, future theoretical work on the evolution of cooperation must distance itself from economics and develop games as a refinement of ethologys comparative approach.

Sexual selection and the evolutionary effects of copying mate choice

We examine the evolutionary consequences of copying mate choice using models in which the preferences of younger females are affected by the mate choices that they observe older females making. We introduce two models of copying, termed “single mate copying” and “mass copying”, corresponding to situations in which immature females imprint on the choices of only one or of a very large number of older females, respectively. Female mating preferences are assumed to evolve only through cultural evolution, while the male trait on which they act is inherited either via a haploid autosomal or a Y-linked locus. Results show that the preference and male trait can rapidly coevolve, with a positive frequencey-dependent advantage to the more common male trait allele. This process can cause a display trait that lowers male viability to increase in a population. Mass copying results in stronger frequency dependence than does single mate copying. Mass copying and, under some conditions, single mate copying lead to two alterative stable equilibria for the male trait. Neither copying model supports variation at the male trait locus, and copying makes it more difficult for a novel male trait phenotype to spread.

Juvenile three-spined sticklebacks avoid parasitized conspecifics

SynopsisJuvenile three-spined sticklebacks,Gasterosteus aculeatus, were given a series of four ‘choice’ tests to determine whether they avoided schools of conspecifics in which individuals were parasitized with the ectoparasiteArgulus canadensis. Results from these tests indicate that juvenile sticklebacks can avoid schools of parasitized conspecifics. Furthermore, parasites alone did not elicit an avoidance response, suggesting that it is both the presence of the parasite and its effect on stickleback behavior that causes avoidance of parasitized individuals.

Fish behaviour, partner choice experiments and cognitive ethology

Points of viewRecently, evidence for ‘partner choice’ in many different contexts (e.g. foraging, anti-predator behaviour) has been accumulating in the fish behavioural ecology literature. In addition to demonstrating relatively complex behaviour in fish, these studies suggest that work on partner choice may benefit by incorporating a cognitive ethological approach to behaviour. We believe that using this approach when studying partner choice, and social behaviour in general, will allow us to address new questions of interest both to fish biologists and to cognitive ethologists.