Eastern Japanese Dictyostelia Species Adapt While Populations Exhibit Neutrality

摘要

The dynamics of biological communities are the result of social interactions among components that span multiple scales. In addition, differences between population-level dynamics and species-level dynamics are poorly understood and have generated ambiguity regarding the concepts of what constitutes a population and a species. In the present study, Dictyostelia was employed as a model community with which to clarify these concepts. The distributions of logarithmically ranked populations could be explained by unified neutral theory and a zero-sum patch game, while distributions of ranked species could not be explained by unified neutral theory. Furthermore, non-metric multidimensional scaling analysis and principal component analysis demonstrated that species occupied distinct niches, supporting the idea that species-level organization could be explained by adaptive structure, while population-level organization could be explained by unified neutral theory. Genetic structures of both populations and species, and the differences in the characteristic time scales of these communities, based on actual and deduced point mutation rates and speciation rates, were also examined. The results indicated that species of eastern Japanese Dictyostelia may have behaved adaptively over a long time scale, while populations may have behaved in accordance with unified neutral theory over a shorter time scale.