Comparative life histories and ecophysiology of Drosophila melanogaster and D. simulans.

Numerous laboratory investigations have compared Drosophila melanogaster and D. simulans for various life history traits and fitness related ecophysiological parameters. From presently available information, it is however difficult to get a general comparative pattern describing the divergence of their ecological niches and understanding their demographic success. Two environmental factors seem however to have played a major role: temperature and alcoholic resources. From an ecophysiological approach, D. simulans may be described as generally more sensitive to stresses; other results point to this species as more cold adapted than its sibling; in some cases, however, D. simulans may appear as better adapted to a warm environment. When investigated, ecophysiological traits show a lesser geographic variability in D. simulans than in D. melanogaster. Presently available information does not explain the ecological prevalence of D. simulans in many places with a mild temperate or subtropical climate. This is presumably due to the fact that most comparisons have been done at a single, standard temperature of 25 degrees C. Comparative studies should be undertaken, spanning the thermal ranges of the two species, and the phenotypic plasticity of ecophysiological traits should now be considered.