Effects Of Niche Partitioning, Dispersal And Spatial Structure Of Metacommunity On Community Repeatability,Rarity And Species-Sorting

Niche and neutral theories have been proposed to explain the community assembly. They can explain the diversity from opposite points:niche theory focuses on the niche partitioning between species while neutral theory emphasizes the ecological equivalent and drift. Here, we study the repeatability of community composition, rarity and species distribution based on these two theories.The repeatability of community composition is theoretically defined as the similarity of community composition among replicate communities which means that the same community repeats many times, assembled under identical conditions. Rare species are those which occur at low frequencies, or with low abundance in samples of a certain size, which is typically small compared with the size of the whole community. Rarity of community is one of the important aspects of species relative abundance distribution. The species-sorting is one of the species distribution pattern, it describes the relationship between species distribution and the environment. All of these describe the structure and assembly process of community from different aspects.Repeatability of community composition is closely associated with community stability, predictability, conservation biology and ecological restoration. It has been shown that both immigration and local dispersal limitation can affect the community composition in both neutral and niche model. Hence, we use a spatially explicit individual-based model to investigate the potential influence of immigration rate and strength of local dispersal limitation on repeatability in both neutral and niche models. We find the correlation between repeatability and immigration rate is positive in the neutral model and an inverted unimodal in the niche model. The correlation between repeatability and local dispersal distance is positive in the niche model and negative in the neutral model. High repeatability between niche communities and neutral communities is observed with high immigration rates or when high local dispersal distance appears in the niche model or low local dispersal distance in the neutral model. Our results show that repeatability of community composition is not only dependent on the types of community models (niche vs. neutrality) but also strongly determined by immigration rates and local dispersal limitation.Both neutral and niche theory have been invoked to explain the rarity of certain species in ecological assemblages:niche theory stresses the importance of the resource division process, while neutral theory focuses on stochastic drift in densities of competitively identical species. Here, we show how migration and niche partitioning can act simultaneously to increase both the number of rare species and the total species richness. By simulating the dynamics of a metacommunity using an interconnected network of local communities, we incorporate niche partitioning into the otherwise per capita equivalent processes of birth and death. For a given niche breadth at the local community scale, unimodal relationships appear between the rate of migration, the number of rare species, and the total species richness. We find that a unimodal relationship between rare species number and migration lead to the appearance of a unimodal correlation between local species richness and migration rate. The integration of niche partitioning and migration therefore provides a rational explanation for the widespread rarity of species in ecological communities.The correspondence between species distribution and the environment depends on species’ ability to track favorable environmental conditions (via dispersal) and to maintain competitive hierarchy against the constant influx of migrants (mass effect) and demographic stochastic (ecological drift). Here we report a simulation study of the influence of landscape structure on species distribution. We consider lottery competition for space in a spatially heterogeneous environment, where the landscape is represented as a network of localities connected by dispersal. We quantified the contribution of neutrality and species sorting to their spatial distribution. We found that neutrality increases and the strength of species-sorting decreases with the centrality of a community in the landscape when the average dispersal among communities is low, whereas the opposite was found at elevated dispersal. We also found that the strength of species-sorting increases with environmental heterogeneity. Our results show that despite species-sorting and ecological drift being conceptually opposite, this relationship does not always hold. In the presence of a strong mass effect, there will be low species-sorting and low neutrality. Our results illustrate that spatial structure of the environment and of dispersal must be taken into account for understanding species distribution.To completely understand the community structure and dynamics, we should do the research based on the integrating niche and neutral theory, and which will be main methods in the future.