Abstract
The role of habitat complexity in the coexistence of ant species is poorly understood. Here, we examine the influence of habitat complexity on coexistence patterns in ant communities of the remote Pacific atoll of Tokelau. The invasive yellow crazy ant, Anoplolepis gracilipes (Smith), exists in high densities on Tokelau, but still coexists with up to seven other epigeic ant species. The size-grain hypothesis (SGH) proposes that as the size of terrestrial walking organisms decreases, the perceived complexity of the environment increases and predicts that: (1) leg length increases allometrically with body size in ants, and (2) coexistence between ant species is facilitated by differential habitat use according to body size. Analysis of morphological variables revealed variation inconsistent with the morphological prediction of the SGH, as leg length increased allometrically with head length only. We also experimentally tested the ability of epigeic ants in the field to discover and dominate food resources in treatments of differing rugosity. A. gracilipes was consistently the first to discover food baits in low rugosity treatments, while smaller ant species were consistently the first to discover food baits in high rugosity treatments. In addition, A. gracilipes dominated food baits in planar treatments, while smaller ant species dominated baits in rugose treatments. We found that the normally predictable outcomes of exploitative competition between A. gracilipes and other ant species were reversed in the high rugosity treatments. Our results support the hypothesis that differential habitat use according to body size provides a mechanism for coexistence with the yellow crazy ant in Tokelau. The SGH may provide a mechanism for coexistence in other ant communities but also in communities of other terrestrial, walking insects that inhabit a complex landscape.
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Acknowledgments
We would like to thank Lloyd Stringer, Kelemete Perez and Mika Perez for field assistance and the Nukunonu Council of Elders and community, without whom this project would not have been possible. John Patterson provided essential technical assistance for which we are grateful. This work was supported by a Victoria University of Wellington Graduate Scholarship to M. Sarty. Funds for research were provided by The Royal Society of New Zealand Marsden Fund and Victoria University of Wellington. All research conducted complied with the current legislation in Tokelau.
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Communicated by Konrad Fiedler
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Sarty, M., Abbott, K.L. & Lester, P.J. Habitat complexity facilitates coexistence in a tropical ant community. Oecologia 149, 465–473 (2006). https://doi.org/10.1007/s00442-006-0453-9
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DOI: https://doi.org/10.1007/s00442-006-0453-9