| Summary: | Metacommunity theory has advanced understanding of mechanisms shaping community structure. Four main models (neutral, patch-dynamics, species-sorting, and mass-effects) have been recognized to explain these mechanisms, differing in their assumptions about the effects of environmental filtering and species traits on community composition. Here, I focus on complex, three-dimensional spider webs of two social and two solitary species as habitat patches for associated arthropods in a tropical rainforest in Ecuador. I used variance partitioning and various analyses of metacommunity structure to study the role of environmental filtering and dispersal in this system. I found that local patch characteristics, such as patch size and host species, predominantly affected local community composition. Webs of social spider species had higher richness, more variable communities, and proportionally more aggressive (i.e. predatory) web associates. Behavioral characteristics of the host spiders, such as sociality and aggressiveness, seemed to play an important role, as well, in shaping community composition on these patches. In a colonization experiment, there was indication of high dispersal rates at a short temporal scale and some evidence of species dominance at a longer temporal scale. I conclude that environmental filtering is responsible for the patterns of species distribution and that, given the conjunctive high dispersal and species specialization, the metacommunity patterns in this system seem to best be explained by a combination of the species sorting and mass effects models. === Science, Faculty of === Zoology, Department of === Graduate
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