Considering ecological neutrality (all species are functionally equivalence) has been effective null hypothesis to know the community assembly mechanisms. Generally, concept of neutrality is used to detect how environmental conditions (and functional traits related to environment) determine the community composition. In this context, dispersal process is assumed to be neutral between species. But in reality, differences in species dispersal ability (related to dispersal traits) is important factor to determine the community composition.
　In this study, we defined “neutrality” on both environment related traits and dispersal related traits to detect the differences in importance of species identity among two hierarchal assembly processes. To assess the dispersal process properly, we researched 433 vegetation patches (completely separate each other) at “patchy tundra vegetation” in northern Canada at three spatial scales (150m, 2km, 20km).
　As expected from earlier study, community composition is largely explained by environmental conditions at every spatial scale (environmental trait-based assembly). On the other hands, the differences in dispersal ability didn’t explain the community composition in any spatial scale (dispersal trait-neutral assembly). In theory, plant community in arctic area was thought to be more predictable by species ecological trait, but in terms of dispersal traits, it did not matter (neutral) in community assembly.