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The mathematical model presented here aims to elucidate the essential mechanisms of coexistence of species, especially those
of closely related forms, as a result of competition in the same environment. It describes a system where the fate of the
competitors or mutants is observed at the initial stage of evolution. The model encompasses both the external variables and
the internal state of the competitors, which differ only in one of the metabolic rate constants. Results of simulations, even
with the simplified form of the model, show that stable coexistence of closely related forms in a uniform environment is possible.
In addition, the model allows the analysis of the limitations on the level of differences and similarities among the competitors
for achieving a state of coexistence. The essential mechanisms for the coexistence of closely related competitors are proposed
to be the involvement of the metabolic network in allowing the same growth rate of competitors which have different internal
states, and the interplay between the internal states of the competitors and the external variables of their environment. 相似文献
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Wei-Zhong Xu Akiko Kashiwagi Tetsuya Yomo Itaru Urabe 《Researches on Population Ecology》1996,38(2):231-237
A simple system was constructed and used in the experimental elucidation of the fate of a mutant emerging in a population.
ThreeEscherichia coli strains having the same genetic background except for their glutamine synthetase gene were used as model competitors. The
difference in the enzyme gene were introduced by random mutation. Competition between these bacterial strains was carried
out and observed in a continuous liquid culture. In most cases, the competitors stably coexist either in a steady state or
in an oscillating state. In addition, the competition between the strains was found to be a deterministic process and not
a stochastic one. These results showed that an emerging mutant in a population, be it a closely related one to the original
members, can attain a state of stable coexistence even in a homogeneous environment. The ability of each of the emerging mutants
to maintain its stable coexistence with the original population gives rise to the accumulation of various mutants in a population.
Therefore, evolution starts from gradual accumulation of various mutants in the population, which in turn leads to the diversification
of the population. As our experimental system is a minimum model for the various competitions in the natural ecosystem, the
observed competitive coexistence is proposed to be a general phenomenon in nature. 相似文献
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Akiko Kashiwagi Tadashi Kanaya Tetsuya Yomo Itaru Urabe 《Researches on Population Ecology》1998,40(2):223-226
Closely related competitors comprising ofEscherichia coli strains having the same metabolic system and differing only with a few bases on the glutamine synthetase gene in the plasmid
pKGN were previously shown to coexist in a chemostat. The differences among these closely related competitors can be considered
large enough to allow coexistence as the level of enzyme activity is different. To bring the difference among competitors
to the slightest possible, the mutation was introduced on the noncoding region of the plasmid pKGN harbored in the wild-type
strain (strain W). The new strain, strain W’, carries the plasmid pKGN’ with a 4-base insertion at theHind III site in the polycloning site of pKGN. As the noncoding region is a nucleotide segment that is not translated into amino
acids, the relatedness between strains W and W’ is the closest possible from the genetic point of view. Interestingly, though
both strains are almost identical, they can coexist stably in a chemostat irrespective of the initial population size. These
experimental results suggest that in the natural ecosystem, no matter how akin competitors are, coexistence is not impossible. 相似文献
4.
Yanagi Itaru Kobashi Yohei Pekkanen Robert J. Tsujinaka Yutaka 《Voluntas: International Journal of Voluntary and Nonprofit Organizations》2021,32(3):534-547
VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - This study innovates by introducing a conceptual distinction between the provision of public services and the receipt of... 相似文献
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