Relating temporal changes in species dispersion and inter-specific associations in successional plant communities to mechanisms of community assembly.
Waugh, Jennifer*,1, Aarssen, Lonnie1, 1 Department of Biology, Kingston, Ontario, Canada
ABSTRACT- If neutral theory predicts the same spatial patterns observed in natural communities traditionally attributed to niche theory, how can the two mechanisms be separated? We suggest that neutral-based mechanisms should have a different temporal 'signature' from niche-based mechanisms in the development of spatial patterns in community structure. More specifically, we ask if the directionality of changes in patterns of species dispersion and species associations through time can be used to infer the relative likelihood of niche- vs. neutral-based assembly in plant communities. To address this question, nearest neighbour point sampling was conducted on a sand dune chronosequence established as a site proceeding through primary succession. The pattern of change in species dispersion during community development was evaluated by comparing, across the chronosequence, the relative distance to intra-specific neighbours versus distance to inter-specific neighbours. Similarly, evidence for the development of directionality (i.e. positive or negative) in species associations during community development was assessed by comparing changes in the nearest neighbour diversity across the chronosequence, quantified by randomization of observed nearest neighbour identities. The temporal pattern in species dispersion was more consistent with a neutral-based mechanism, with individuals becoming less intra-specifically clumped in successive time periods. Similarly, the proportion of directional species associations decreased with time, thus providing no evidence for the role of spatial niche differentiation in the process of species assembly over time.
Key words: succession, community assembly, niche, neutral communities
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