Ants as Ecosystem Engineers

Comanche harvester ant (Pogonomyrmex comanche) nest year

Comanche harvester ant (Pogonomyrmex comanche) nest year

Many ant species are ecosystem engineers. An ecosystem engineer is an organism which structures the environment to suit its needs and in doing so has profound effects on the occurrence, abundance, and spatial pattern of other species. Beavers, who turn streams into ponds, are the textbook example. Ants do exactly the same thing in soil. They are soil engineers. Through their nesting habits, ants are agents of bioturbation, mixing soil horizons and creating avenues for water and gas exchange through the tunnels and chambers that make up their nest architecture. These activities result in soil production and altering soil chemical, physical, and biotic profiles.

nest casts

Their movement of materials from above and below ground concentrates nutrients and minerals in the nest and associated soil. The above ground nest structure is engineered as well. By creating soil or other mound structures, the ants may prevent plant colonization and change soil temperature and moisture profiles. The addition of pebbles to nest mounds done by Pogonomyrmex barbatus and P. rugosus, for instance, changes the temperature of the upper region of the nests. These species intentionally forage pebbles from the environment to do so. The parasitic, commensalist and mutualist organisms which may share these nests change the soil communities since these species would not be present at all without the ants.

Todd Island (TI-1) site at the Fort Worth Nature Center, Fort Worth, Texas. Note the Comanche harvester ant nest in the bare area, lower left.

Todd Island (TI-1) site at the Fort Worth Nature Center, Fort Worth, Texas. Note the Comanche harvester ant nest in the bare area, lower left.

Through all these activities ants engineer the soil to be suitable for the internal environment of their nests insuring the development of their young and their own survival. Because of this soil engineering, the occurrence, abundance, and spatial pattern of soil organisms and therefore the soil community are significantly different in areas with ant nests and those without. In turn, the differences in the soil community affect soil nutrient cycling and availability which affects these communities as well as the plant community which has a large portion of their bodies above ground. When an ant colony dies or moves, the nest area becomes available for colonization. As a result of the far reaching impacts of their engineering, ants have been used as indicators of ecosystem health and function, specifically tracking the progression through climax stages and in remediation of mining sites specifically due to soil production and engineering activities of ants.

The external nest of a Comanche harvester ant. The ants remove any plants from this nest yard area.

The external nest of a Comanche harvester ant. The ants remove any plants from this nest yard area.

Here I have focused mostly on the engineering of ground nesting ants on soil and provided photo of Pogonomyrmex comanche nests. Ant engineering may include many other ant species and other ecosystem impacts such as foraging activities including vegetation clearing on foraging areas and trails and foraging on seed and vegetative parts through which ants can impact plant populations and communities.

Because ants are central place animals, like beaver, their engineering is of local significance and contributes to the importance of spatial ecology for understanding ecosystem function and health.

 

Selected Literature

Andersen, A.N. 1990. The use of ant communities to evaluate change in Australian terrestrial ecosystems: a review and a recipe. Proceedings of the Ecological Society of Australia 16: 347 – 357.

Bucy, A. M. and Breed, M. D. 2006. Thermoregulatory trade-offs result from vegetation removal by a harvester ant. Ecological Entomology 31: 423 – 429.

Carlson, S. R. and Whitford, W. G. 1991. Ant mound influence on vegetation and soils in a semiarid mountain ecosystem. American Midland Naturalist 126: 125 – 139.

Cox, M. G. and Blanchard, G. B. 2000. Gaseous templates in ant nests. Journal of Theoretical Biology 204: 223 -238.

Dean, W. R. J., Milton, S. J., and Klotz, S. 1997. The role of ant nest-mounds in maintaining small-scale patchiness in dry grassland in Central Germany. Biodiversity and Conservation 6: 1293 – 1307.

de Bruyn, L. A. L. 1999. Ants as bioindicators of soil function in rural environments. Agriculture, Ecosystems, and Environment 74: 425 – 441.

Dostal, P., Brezniva, M., Kozlickova, V., Herben, T. and Hovar, P. 2005. Ant-induced soil modification and its effect on plant below-ground biomass. Pedobiologia 49: 127 – 137.

Eldridge, D. J. 1993. Effects on ants on sandy soils in semiarid eastern Australia: local distribution of nest entrances and their effect in the infiltration of water. Australian Journal of Soil Research 31: 509 – 518.

Elmes, G. W. 1991. Ant colonies and environmental disturbance. In: The Environmental Impact of Burrowing Animals and Animal Burrows [Symposium of the Zoological Society of London 63]. Clarendon Press: Oxford, UK. p. 15 – 32. Clarendon Press: Oxford, UK.

Folgarait, P. J. 1998. Ant biodiversity and its relationship to ecosystem functioning: a review. Biodiversity and Conservation 7: 1221 – 1244.

Hendricks, P. and Hendricks, L. M. 1999. Field observations on the myrmecophilous beetle Araeoschizus airmeti Tanner (Coleoptera: Tenebrionidae) at harvester ant mounds (Hymenoptera, Formicidae) mounds. Great Basin Naturalist 59: 297 – 299.

Lesica, P. and Kannowski, P. B. 1998. Ants create hummocks and alter structure and vegetation of a mountain fen. American Midland Naturalist 139: 58 – 68.

MacMahon, J. A., Mull, J. F., and Crist, T. O. 2000. Harvester ants (Pogonomyrmex spp.): their community and ecosystem influences. Annual Review of Ecology and Systematics 31: 265 – 291.

New, T. R. 2000. How useful are ant assemblages for monitoring habitat disturbance on grasslands in south eastern Australia. Journal of Insect Conservation 4: 153 – 159.

Nikem, J. N., Lobry de Bruyn, L. A., Grant, C. D., and Hulugalle, N. R. 2000. The impact of ant bioturbation and foraging activities on surrounding soil properties. Pedobiologia 44: 60 9 – 621.

Pisani, G. R. 2009. Use of an active ant nest as a hibernaculum by small snake species. Transactions of the Kansas Academy of Science 112: 113 – 118.

Ríos-Casanova, L. Valiente-Banuet, and A., Rico-Gray. 2006. Ant diversity and its relationship with vegetation and soil factors in an alluvial fan of the Techuacán Valley, Mexico. Acta Oecologica 29: 316 – 323.

Smith, C. C. 1940. Biotic and physiographic succession on abandoned eroded farmland. Ecological Monographs 10: 421 – 484.

Snyder, S. R. and Friese, C. F. 2001. A survey of arbuscular mycorrhizal fungus root inoculums associated with harvester ant nests (Pogonomyrmex occidentalis) across the western United States. Mycorrhiza 11: 163 – 165.

Trager, J. C. 1990. Restored prairie colonized by native prairie ants (Missouri, Illinois). Restoration and Management Notes 8: 104 – 105.

Underwood, E. C. and Fisher, B. L. 2006. The role of ants in conservation monitoring: if, when, and how. Biological Conservation 132: 166 – 182.