MODELING AND ANALYZING DENSITY-DEPENDENT POPULATION PROCESSES - COMPARISON BETWEEN WILD AND LABORATORY STRAINS OF THE BEAN WEEVIL, CALLOSOBRUCHUS-CHINENSIS (L)

Three models were constructed for analyzing the population characteris tics of C. chinensis on stored beans; model A describing the whole rep roductive process with a single equation, model B describing the three age-specific processes (oviposition, egg survival and larval survival ) with separate equations, and model C which describes all these proce sses not for the whole habitat but for the individual beans comprizing it. The logit equation was employed here as a common basis to describ e the density-response relationship involved. All three models showed very good fit to the experimental data obtained for both laboratory an d wild strains of the weevil. The parameter values characterizing the population dynamics were, however, widely different between the two st rains; the laboratory one which had been reared for some 500 generatio ns showed significantly higher reproductive capacity, less sensitive a nd gentler response to crowding in both adult and egg stages, and more uniform egg distribution among individual beans, as compared with the wild strain newly introduced. Sensitivity analyses using these models suggested that these changes in population characteristics have been attained by the process of domestication or adaptation to stable labor atory conditions through a long period of time. This process seemed in effect to have optimized the population's performances in the laborat ory environment. Evolutionary significance of such optimization was di scussed with reference to the selection pressure which may have acted upon individuals.