. This paper investigates cooperative behavior in an artificial ecology.in which egoistic agents interact-with each other through a tournament of iterated games..The tournament played is a variant of the Axelrod (1984) iterated prisoner's dilemma (IPD) game,modified to permit players to choose and refuse potential game.partners. In each iteration, players use expected payoffs updated on'the basis of past encounters to make prisoner's dilemma game offers to a limited number of preferred players, and to refuse prisoner's, dilemma game offers from unacceptable players...