Effect of Contest and Scramble Competition on Population Dynamics.

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1. Using the two bruchid species, a contest type strategist (Callosobruchus analis), and a scramble type strategist (C. phaseoli), I investigated the aggressive behavior of their larvae. The third and fourth instar larvae of C. analis showed the strong aggressive behavior against conspecific and heterospecific larvae alike. No such aggressive behavior was observed at any larval stages of C. phaseoli.2. I performed multi-generation interspecific competition experiment between C. analis and C. phaseoli, using mung bean (Vigna radiata) as their resource. With large sized beans, C. analis was eliminated from the system within 200 days. With small sized beans, C. phaseoli was eliminated within 200 days. With mixture of equal amount of beans of the two sizes, the two species coexisted for more than 460 days. These results were fully explainable from the results of behavioral observations conducted in 1.3. Using the two strains of C. maculatus, one with contest type strategy and the other wit … More h scramble type strategy, I investigated the genetic mechanism of aggressive behavior. The genes responsible was shown to be additive multiple genes.4. I investigated the larval aggressive behavior of the above two strains. The contest type strain showed the aggressive behavior all through their larval stages. The scramble type strain showed the aggressive behavior only in their late larva stage. These results are quite different from those of C. analis and C. phaseoli observed in 1.5. I conducted multi-generation intraspecific competition experiment between the two strains of C. maculatus, similar to that done in 2. In terms of population size, the system converged to scramble type with small beans, and it converged to contest type with small beans. With mixed beans, the system showed the coexistence of the two strategist types. When the genetic structure of the individuals in the system was analyzed by backcrossing them to those of stock cultures, the system with large beans was shown to have converged to scramble type. However, with small beans and with mixed beans, the individuals in the systems showed the same genetic structure as those seen in F_1 individuals between scramble and contest types. Less