Material cycling and population interactions in food webs, and the evolutionary dynamics of biological communities

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This project was to promote ecological studies that analyzes the structure and dynamics of biological communities and food webs in relation to material cycling, interactions among organisms, and evolution of traits associated with resource uses and interspecific interactions. We investigated aquatic communities in natural phytotelmata and in laboratory microcosms as model systems because they possess essential properties of ecological systems, especially environmental patchiness, and are manipulable small, semiclosed systems which are suitable to both field and laboratory studies. In natural phytotelmata including treeholes, bamboo stumps, and pitcher plants, we found several important community properties. (1) In individual phytotelmata, the amount of detritus and stability of aquatic site were correlated with phytotelm size, and the phytotelm size was correlated with biomass and species richness. Thus, local communities were space and/or resource limited. (2) Species interactions (pr … More edation and competition) in local communities occurred among restricted small sets of species ; aggregated distribution in each species and random association between species often resulted in reduced interspecific interactions which might promote species coexistence. (3) Despite the local limitation of community diversity, regional species richness could be maintained in patchy environments, because the patchiness reduces overall strength of interspecific interactions and environmental heterogeneity involved allows niche segregation among species. (4) Evolutionary divergence of life-history and physiological traits, especially in habitat selection and the allocation of energy to foraging, development and growth, and survival, could leads to coexistence of competing species. In microcosm experiments, the importance of microbial loop was emphasized. The use of bacteria by crustaceans as food resources was studied in terms of foraging behavior and nutritional value. A cladocera had a fine trapping mechanism for bacteria. Also, invadability of bacteria into novel environments was studied in relation to application of genetically-engineered useful bacteria for restoring polluted environments. Mathematical models of interacting organisms and food webs in patchy environments are now analyzed to predict evolutionary dynamics of community and food web structures. Less