The role of prey size and abundance in the geographical distribution of spider sociality

Authors

  • KIMBERLY S. POWERS,

    1. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA,
    2. David Evans and Associates, Inc., 2100 River Parkway, Portland, OR 97201, USA
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  • LETICIA AVILÉS

    1. Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA,
    2. Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; and
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Leticia Avilés, Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada (e-mail: laviles@zoology.ubc.ca).

Summary

  • 1Social species in the spider genus Anelosimus predominate in lowland tropical rainforests, while congeneric subsocial species occur at higher elevations or higher latitudes.
  • 2We conducted a comparative study to determine whether differences in total biomass, insect size or both have been responsible for this pattern.
  • 3We found that larger average insect size, rather than greater overall biomass per se, is a key characteristic of lowland tropical habitats correlating with greater sociality.
  • 4Social species occupied environments with insects several times larger than the spiders, while subsocial species nearing dispersal occupied environments with smaller insects in either high or low overall biomass.
  • 5Similarly, in subsocial spider colonies, individuals lived communally at a time when they were younger and therefore smaller than the average insect landing on their webs.
  • 6We thus suggest that the availability of large insects may be a critical factor restricting social species to their lowland tropical habitats.

Ancillary