Neutral ecological drift, more than environmental factors, explains changes in plant community composition.
Link-Perez, Melanie*,1, Stevens, M. Henry1, 1 Miami University, Oxford, Ohio, USA
ABSTRACT- Neutral community models recognize the potential importance of dispersal limitation in structuring plant communities. According to neutral theory, geographic distance is a good predictor of plant community composition, since dispersal limitation is a mechanism of neutral ecological drift. On the other hand, classical niche theory suggests that soil characteristics determine community composition. We describe the change in species composition with distance in two prairie communities–one relict, one reconstructed–and compare the observed patterns of diversity with theoretical predictions derived from neutral theory. We sampled vegetation and soil characteristics in 2.5 m2 plots separated by 0-166 m. The relict prairie is a natural community: neutral theory predicts that dispersal limitation will affect community composition and similarity will decrease with distance. The 7-year-old reconstructed prairie offers, in contrast, a site where dispersal limitation at time of initial planting was absent: neutral theory predicts little change in similarity with distance. Simple and partial Mantel tests were performed on distance matrices of the cover class data for vegetation, the standardized data for thirteen environmental variables, and geographic coordinates. We found that in both prairies geographic distance was a better predictor of community dissimilarity than were environmental variables. In addition, geographic distance explained more variability in community dissimilarity in the older relict prairie than in the younger reconstructed prairie. These findings indicate that dispersal limitation and neutral ecological drift play a stronger role than environmental variables in structuring plant communities at these spatial scales.
Key words: neutral theory, niche, spatial patterns, beta diversity
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