Habitat heterogeneity and niche structure of trees in two tropical rain forests.
Dispersal-assembly theories of species coexistence posit that environmental factors play no role in explaining community diversity and structure. Dispersal-assembly theories shed light on some aspects of community structure such as species-area and species-abundance relationships. However, species' environmental associations also affect these measures of community structure. Measurements of species' niche breadth and overlap address this influence. Using a new continuous measure of niche and a dispersal-assembly null model that maintains species' niche breadth and aggregation, we tested two hypotheses assessing the effects of habitat heterogeneity on the ability of dispersal-assembly theories to explain community niche structure. We found that in both homogenous and heterogeneous environments dispersal-assembly theories cannot fully explain observed niche structure. The performance of the dispersal-assembly null models was particularly poor in heterogeneous environments. These results indicate that non-dispersal based mechanisms are in part responsible for observed community structure and measures of community structure which include species' environmental associations should be used to test theories of species diversity.
Potts
Matthew D
MD
Institute on Global Conflict and Cooperation, University of California San Diego, La Jolla, CA 92039, USA.
Davies
Stuart J
SJ
Bossert
William H
WH
Tan
S
S
Nur Supardi
M N
MN
D000531:Altitude; D003710:Demography; D017753:Ecosystem; D004777:Environment; D008296:Malaysia; D008962:Models, Theoretical; D014197:Trees; D014329:Tropical Climate