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Drosophila Population Dynamics: Chaos and Extinction
Author(s) -
Philippi Thomas E.,
Carpenter M. Patricia,
Case Ted J.,
Gilpin Michael E.
Publication year - 1987
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1938815
Subject(s) - carrying capacity , population , extinction (optical mineralogy) , statistical physics , logistic function , ecology , robustness (evolution) , chaotic , biology , stability (learning theory) , statistics , econometrics , mathematics , physics , computer science , demography , paleontology , biochemistry , artificial intelligence , machine learning , sociology , gene
Earlier work in our laboratory and others suggests that the discrete population dynamics of serial transfer Drosophila systems are stable, despite observed fluctuations about the carrying capacity. To investigate the robustness of this conclusion, we have radically reduced the available food in the system (from 40 to 3 mL of media). The number of flies in such systems fluctuates to such an extent that they go extinct. To investigate whether this is due to chaotic population dynamics, as opposed to environmental or demographic stochasticity, we fitted the discrete Q—logistic growth equation to data from i nput—output" experiments (i.e., experiments in which we recorded survivorship and recruitment in systems at eight starting densities) and compared the calculated parameters to previous work in our laboratory. Surprisingly, the resulting parameters for the mean behavior of our t hin—food systems indicated greater stability than those for previous t hick—foodsystems. Thus, the observed fluctuations and extinctions may be explained on the basis of a reduced carrying capacity and an increased variance of growth dynamics (environmental stochasticity). We have corroborated this with an empirically based computer model incorporating stochasticity. This work has implications for the problem of minimum viable population size