Sociality and resource use: insights from a community of social spiders in Brazil

We explored the role of group living and cooperation in resource use in a spider community where 4 congeneric species of similar body size, but with behaviors ranging from near-solitary to fully social, co-occur. We found that the range of insect sizes captured by each species reflected their nest and colony size so that species with larger colonies and prey capture webs captured larger insects than less social species. Yet, among those species whose webs did not differ significantly in size--the 2 with the largest and the 2 with the smallest webs--one captured significantly larger insects than the other. This pattern was apparently due to differences in the extent to which nest mates cooperated in the capture of prey, as in only one of the species in each pair did the size of the insects captured increase with colony size. The 4 species were thus packed along the spectrum of available insect sizes from least to most social, with limited overlap between contiguous species. The pattern of resource use was thus more overdispersed than expected by chance, as would be expected if the species had been assembled or differentiated to avoid extensive dietary overlap. We consider alternative hypotheses to explain these patterns and suggest that group size and level of cooperation may play an important role in the dietary segregation of sympatric organisms. Copyright 2011, Oxford University Press.