Analyses of life histories

There are signs that the integration of genetics at the population level with ecology that is needed for a coherent evolutionary biology of populations is beginning (Jain, 1979; Price, 1980; Parsons, 1982a). Population geneticists frequently choose clear-cut genetic markers – chromosomal inversions, recessive lethals, and electrophoretic variants – in order to study population variability. Having assayed variability, a search is made for the ecological significance of the variability patterns, almost as a second-order situation. By contrast, the ecologist takes traits of obvious adaptive significance in determining the distribution and abundance of organisms; the genetic basis of the traits is not often considered. Following Jain (1979), who was mainly considering plants, analyses of adaptation should proceed with (1) comparative studies of variation of several well-chosen traits, (2) the establishment of adaptive roles of these traits, (3) the demonstration of genetic changes under varying environments, and (4) the experimental demonstration of whether the outcomes represent adequate solutions to an adaptive challenge. Until recently, points (2) to (4) were not often considered, but the situation is beginning to change in that regard. This means that inferences are often speculative, since these omissions mean that genetic aspects tend to be given little emphasis – a conclusion that applies to animals and plants alike.