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A Case Study in Experimental Evolution: Reproductive Effort and Induced Responses in Drosophila melanogaster
Author(s) -
STEARNS STEPHEN C.,
KAISER MARCEL,
BLARER ALBERT
Publication year - 1996
Publication title -
plant species biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.419
H-Index - 36
eISSN - 1442-1984
pISSN - 0913-557X
DOI - 10.1111/j.1442-1984.1996.tb00112.x
Subject(s) - fecundity , biology , drosophila melanogaster , ageing , longevity , larva , mortality rate , reproduction , physiology , zoology , demography , experimental evolution , reproductive value , evolutionary biology , ecology , genetics , population , offspring , pregnancy , gene , sociology
To understand the causes of tradeoffs, particularly those involved in ageing, to test the reproductive effort model of life history evolution, and to measure the rate of evolution of induced life history responses, we have been performing an artificial selection experiment on Drosophila melanogaster since November 1993. It consists of four treatments, each with three replicates. The first treatment consists of constant high adult mortality; the second treatment of constant low adult mortality. In all four treatments, propyl acetate is present in the medium for 4 weeks, then absent for 4 weeks. In the third treatment, propyl acetate in the larval medium is associated with high adult mortality. In the fourth treatment, propyl acetate is associated with low adult mortality. To ensure that the effects of treatments are due to differences in mortality and not in density, adult and larval density are kept the same in all treatments. In the first two treatments, the evolution of reproductive effort and age and size at maturity has been rapid and has confirmed the predictions of the reproductive effort model. The relationships between age and size at eclosion and between size at eclosion and fecundity have also evolved. Because the only difference between the first two treatments was the level of adult mortality, this establishes differences in mortality rates as a sufficient cause for the evolution of age and size at eclosion and for the age‐distribution of fecundity rates. In the second two treatments, the evolution of induced responses has been slow, and responses are not yet consistent. The reasons for the slower evolution of induced responses suggest two new theoretical questions.