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DENSITY‐DEPENDENT NATURAL SELECTION IN DROSOPHILA : EVOLUTION OF GROWTH RATE AND BODY SIZE
Author(s) -
Santos Mauro,
Borash Daniel J.,
Joshi Amitabh,
Bounlutay Nira,
Mueller Laurence D.
Publication year - 1997
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.1997.tb02429.x
Subject(s) - biology , larva , natural selection , drosophila melanogaster , selection (genetic algorithm) , ecology , experimental evolution , population , zoology , biomass (ecology) , natural population growth , body weight , population density , evolutionary biology , demography , genetics , artificial intelligence , sociology , computer science , gene , endocrinology
Drosophila melanogaster populations subjected to extreme larval crowding (CU lines) in our laboratory have evolved higher larval feeding rates than their corresponding controls (UU lines). It has been suggested that this genetically based behavior may involve an energetic cost, which precludes natural selection in a density‐regulated population to simultaneously maximize food acquisition and food conversion into biomass. If true, this stands against some basic predictions of the general theory of density‐dependent natural selection. Here we investigate the evolutionary consequences of density‐dependent natural selection on growth rate and body size in D. melanogaster. The CU populations showed a higher growth rate during the postcritical period of larval life than UU populations, but the sustained differences in weight did not translate into the adult stage. The simplest explanation for these findings (that natural selection in a crowded larval environment favors a faster food acquisition for the individual to attain the same final body size in a shorter period of time) was tested and rejected by looking at the larva‐to‐adult development times. Larvae of CU populations starved for different periods of time develop into comparatively smaller adults, suggesting that food seeking behavior in a food depleted environment carries a higher cost to these larvae than to their UU counterparts. The results have important implications for understanding the evolution of body size in natural populations of Drosophila , and stand against some widespread beliefs that body size may represent a compromise between the conflicting effects of genetic variation in larval and adult performance.