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DENSITY‐DEPENDENT EVOLUTION OF LIFE‐HISTORY TRAITS IN DROSOPHILA MELANOGASTER
Author(s) -
Bierbaum Todd J.,
Mueller Laurence D.,
Ayala Francisco J.
Publication year - 1989
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.1558-5646.1989.tb04234.x
Subject(s) - biology , fecundity , longevity , larva , selection (genetic algorithm) , survivorship curve , drosophila melanogaster , density dependence , trait , life history theory , population , population density , ecology , zoology , evolutionary biology , life history , demography , genetics , gene , cancer , artificial intelligence , sociology , computer science , programming language
Populations of Drosophila melanogaster were maintained for 36 generations in r‐ and K ‐selected environments in order to test the life‐history predictions of theories on density‐dependent selection. In the r ‐selection environment, populations were reduced to low densities by density‐independent adult mortality, whereas populations in the K ‐selection environment were maintained at their carrying capacity. Some of the experimental results support the predictions or r‐ and K ‐selection theory; relative to the r ‐selected populations, the K ‐selected populations evolved an increased larval‐to‐adult viability, larger body size, and longer development time at high larval densities. Mueller and Ayala (1981) found that K ‐selected populations also have a higher rate of population growth at high densities. Other predictions of the thoery are contradicted by the lack of differences between the r and K populations in adult longevity and fecundity and a slower rate of development for r ‐selected individuals at low densities. The differences between selected populations in larval survivorship, larval‐to‐adult development time, and adult body size are strongly dependent on larval density, and there is a significant interaction between populations and larval density for each trait. This manifests an inadequacy of the theory on r‐ and K ‐selection, which does not take into account such interactions between genotypes and environments. We describe mechanisms that may explain the evolution of preadult life‐history traits in our experiment and discuss the need for changes in theories of density‐dependent selection.