Efficiency of biomass transfer and the stability of model food-webs |
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Authors: | RSM Kirkwood JH Lawton |
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Institution: | Department of Biology, University of York, Heslington, York, YO1 5DD, England |
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Abstract: | Low efficiency of biomass transfer between trophic levels was found to enhance the stability of a model ecosystem in Lotka-Volterra form, consisting of six basal species, three primary consumers and an omnivore (De Angelis, 1975). The present paper extends De Angelis's result to a more general class of models, varying in species number, connectance and precise features of web design. Whilst the efficiency of biomass transfer does influence stability, it does not do so in the relatively simple way proposed by De Angelis. Three ranges of maximum efficiency of biomass transfer, γmax, were employed, biologically probable (1 > γmax > 0· 1), possible to very unlikely (0 · 1 > γmax>0 · 01) and highly improbable (0.01> γmax> 0· 001). Over most web configurations, in biologically probable regions of ymax, increasing connectance decreased the probability of webstability—the opposite of De Angelis's prediction. Increasing connectance only enhanced stability in biologically unrealistic regions of γmax. Stability was also markedly influenced in these models by the number of component species and trophic levels in the web, features not evaluated by De Angelis. Low efficiency of biomass transfer enhanced stability in some types of web, but not in others. |
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