Eastern Japanese Dictyostelia Species Adapt While Populations Exhibit Neutrality
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RESEARCH ARTICLE
Eastern Japanese Dictyostelia Species Adapt While Populations Exhibit Neutrality Shun Adachi
Received: 3 June 2014 / Accepted: 22 February 2015 Ó Springer Science+Business Media New York 2015
Abstract 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, nonmetric 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.
Electronic supplementary material The online version of this article (doi:10.1007/s11692-015-9312-0) contains supplementary material, which is available to authorized users. S. Adachi (&) Medical Research Project, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramotocho, Tokushima 770-8503, Japan e-mail: [email protected]
Keywords Biological community Population Species Unified neutral theory 18S ribosomal RNA (18S rRNA) Internal transcribed spacer (ITS)
Introduction In nature, population dynamics are defined as the change in population numbers over time, and individuals are characterized by their intrinsic physiologies and their interactions with other individuals. The studies of molecular biology and ecology have facilitated a greater understanding of certain roles of the organizational communities; however, the existence and precise definition of higherorder communities, such as species, remains poorly understood and has resulted in long-standing debates among biologists (Coyne and Orr 2004; Whitham et al. 2006). Populations are often defined within the context of both ecology and demographics, such as by Krebs (1972; p. 139), who defined a population as ‘‘a group of organisms of the same species occupying a particular space at a particular time’’. This qualitative definition allows different groups of researchers to define populations in
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