Wednesday, 20 November 2002 - 8:36 AM

This presentation is part of : Apiculture and Social Insects (Ants et al.)

Semi-claustral colony founding in the seed-harvester ant Pogonomyrmex californicus: a comparative analysis of colony founding strategies

Robert A. Johnson, Department of Biology, Arizona State University, Department of Biology, Social Insect Research Group, Tempe, AZ

The evolution of fully claustral queens is viewed as a major advance for higher ants because it eliminated the need for queens to forage. In an apparently unusual secondary modification, the seed-harvester ant Pogonomyrmex californicus displays obligate queen foraging, i.e., queens must forage to garner the resources necessary to rear their first brood. I examined the potential benefits of queen foraging by comparing ecological and physiological traits between P. californicus queens and several congeners in which single queens rear brood using only body reserves. The primary advantage of foraging appears to lie in providing the queens of P. californicus with the energy to raise significantly more brood than possible by fully claustral congeners; these workers were also heavier in mass than that predicted by their head width. Other correlates of queen foraging included a small queen body size and a low percentage content for total fats and storage proteins.

This life history scenario contrasts with a divergent population of P. californicus in southern California, in which queens differ in founding behavior and other life history traits. A low percentage of these queens can rear brood without an external food source, apparently because of the additional energy reserves supplied by a larger body size and higher fat content. Queens also forage in other well-studied species of Pogonomyrmex, suggesting that queen foraging may be more common than previously thought in higher ants. Overall, the genus Pogonomyrmex offers a diverse system to understand the evolution of nest founding strategies.

Species 1: Hymenoptera Formicidae Pogonomyrmex californicus (California harvester ant)
Keywords: queen foraging, brood production

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