Spider sociality and community assembly

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The question of what determines the composition of plant and animal communities is central to ecology, but one not easily addressed given the large spatial scales and difficult manipulation of most systems. Social spiders, and the inquilines that colonize their webs, are tractable systems to address key questions in community and metacommunity ecology at multiple scales.******Communities of the social spider genus Anelosimus across the Americas exhibit the distinct signatures of environmental filtering at the continental scale and limiting similarity at the local scale. We have shown that the environmental filter reflects broad scale patterns of insect size, precipitation intensity and predation risk, which limit the occurrence of social and subsocial species to certain habitats. We will test the roles of resource partitioning and environmental and temporal heterogeneity in niche differentiation in these communities. We hypothesize that environmental heterogeneity opens up diverse microhabitats to species that differ in body size or level of sociality, which, in turn, differ in the size of prey they capture. To test the hypothesis that environmental heterogeneity and species richness are positively associated, we will characterize the habitats occupied by communities ranging from 1-5 species in Costa Rica/Panama, Ecuador, and Brazil. Within select communities, we will perform reciprocal nest transplant experiments to test the prediction that most functionally dissimilar species exhibit the greatest performance difference in a given microhabitat.******The three-dimensional webs of these social and other spiders harbour inquiline arthropod communities of sufficient distinctness and stability to serve as models for metacommunities. We will investigate the interplay of local and global processes in determining the make up of these communities. We suggest that three-dimensional scaling as a function of host web size interacts with environmental productivity to determine flow of resources to hosts and inquilines. These factors may impact not only the density of inquilines, but also their diversity. Behaviours of the host spiders, such as nest hygiene, may also influence the incidence of certain inquiline types. To test these hypotheses we will assess the composition of inquiline communities, host-inquiline interactions, and flow of resources to hosts and inquilines across elevation and precipitation gradients in Ecuador. By artificially establishing new host webs we will assess the role of local and spatial processes in the make up of these communities. ******The proposed projects pursuit two novel directions to address the question of community compositionrecognizing the importance of level of sociality in community assembly and using the inquiline communities in 3D spider webs as a new empirical system for metacommunity analysis. These two tractable systems make for a powerful combination to tackle one of the central questions in ecology at multiple scales.**