Abstract:
Natural selection, as first independently conceptualized by Darwin (1859) and Wallace
(Darwin and Wallace 1858), aimed to explain the evolutionary changes in biological
populations by differential survival and reproduction among individual organisms. The
principle of natural selection has also provided insights into how life-histories themselves
evolve, in addition to focusing attention on the life-history as the interface between
organismal phenotypes and fitness (Roff 1992; Stearns 1992, 2000). The life-history is
determined by the process of development, age of attaining reproductive maturity,
lifespan, and the number and probability of survival of offspring (Reznick and Travis
1996). Life-history theory attempts to predict the evolution of optimization of the
schedule of survival and reproduction in a given ecological scenario (Stearns 1992, 2000;
Roff 1992).
In an evolutionary utopia, life-histories should evolve to maximize overall fitness i.e.
organisms would start reproducing soon after birth, producing very large numbers of
offspring and survive infinitely. Such a scenario, however, is not possible due to resource
limitation, manifested as trade-offs among fitness-related traits. The understanding of the
evolution of life-history, thus, requires identification of main fitness-related traits and the
genetic correlations among them in the ecological scenario of interest. In this regard,
laboratory selection experiments on life-history related traits have been extremely useful
in investigating the genetic architecture for fitness-related traits in a well defined and
controlled ecology (reviewed in Prasad and Joshi 2003). In particular, such studies on
Drosophila melanogaster have provided important insights into the manner in which
ecology and genetics interact to shape trajectories of adaptive evolution (reviewed in
Prasad and Joshi 2003).
