Resource heterogeneity and community structure: A case study in Heliconia imbricata Phytotelmata

Complex or non-additive differences in the distribution and abundance of arthropod species inhabiting the water-filled bracts of Heliconia imbricata can be created by simple manipulations of resource levels. The primary resources for these assemblages are the corollas of the flowers that accumulate in the bracts. Removing or adding corollas to individual bracts changes the pattern in the abundance of arthropod species within each bract such that bracts with different treatments ultimately differ in composition and numerical associations among species. These results suggest that direct and indirect resource-mediated factors can structure or significantly affect the distribution and abundance of species in these and perhaps other assemblages. Thus, in natural communities, if resources are heterogeneous among patches (such as among the bracts in this study) structure in a given patch may be a function of the resource level of that patch and can differ significantly from neighboring patches that provide different resource levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47788/1/442_2004_Article_BF00665591.pd

Interspecific competition is not a major organizing force in many insect communities

Part of the current dogma in ecology is that competition between species for limited resources is not only common but also a major organizing force in many communities largely because studies on vertebrates, particularly birds, have played a major role in creating the traditional framework of niche theory and resource partitioning. Other workers, particularly those studying insect communities, have suggested that significant interspecific competition is too rare and sporadic to be of major significance and have placed more emphasis on autecological processes. Efforts to resolve the controversy have concentrated on the question of whether or not competition is common in nature. Here we show that even where competition can be demonstrated, it need not have a major role in community organization