The genetic architecture of fitness-related traits in populations of three species of drosophila subjected to selection for adaptation to larval crowding

Abstract

Fitness can be comprehensively defined in terms of reproductive value or the expected future reproductive contribution of an individual, as a function of its age, expectation of survival and expectation of reproduction (Reznick and Travis, 1996). Thus, the study of lifehistory traits like reproductive age, number of offspring, life span and other traits which affect these indirectly, like resistance of an organism to various biotic and abiotic stresses or traits affecting resource acquisition and utilization, is important to both ecology and evolution. However, it was Mac Arthur and Wilson’s (1967) theory of density-dependent selection which for the first time formally brought together population genetics and population ecology, as it considered the impact of population density on evolutionary trends. Since then, many theoretical models have been developed for life-history evolution over the course of time and under different environmental conditions (Gadgil and Bossert, 1970; Roughgarden, 1971; Asmussen, 1983; Boyce, 1984; Charlesworth 1994). These models predict the life-history expected to evolve under some defined selection regime. However, these models typically do not explicitly consider the genetic architecture of fitness-related traits. This lacuna has been addressed by many empirical studies on life-history evolution done in field, semi-natural or laboratory conditions (Rose 1984; Vasi et al. 1994; Hoffmann et al. 2003; van der Linde, 2005; Nussey et al. 2008).