PARENT SESSION
Oral Session 67: Mutualism - Parasitism III: Ants.
Presiding: K Mooney
Wednesday, August 4, 8:00 AM to 11:30 AM, Meeting Room D 135.
Interaction between season and community composition on seed preference by Pogonomyrmex barbataus, red harvester ant.
Nicolai, Nancy*,1, Smeins, F.1, Cook, J.2, 1 Texas A&M University, College Station, TX2 Sam Houston State University, Huntsville, TX
ABSTRACT- The effects of season and community composition on seed species preference by Pogonomyrmex barbatus (red harvester ant) was studied by field experimentation in a southern mixed prairie of central Texas. P. barbatus raise their brood during the spring and prepare for winter's dormancy during the fall. Seasonal differences in nutrient requirements of the nest could lead to differential preferences in seed species harvested in different seasons. Cafeteria studies were conducted on seed selection by comparing seed removal among known quantities of different species in heavily grazed and ungrazed communities during spring and fall, 2003. Commercial seeds of known nutrient content and native species were tested. Additionally, seeds were collected from returning foragers. Total seed harvest was higher in the spring than fall. Preferences were significantly different among native seeds in both seasons, depending on the grazing treatment/community. Seeds of known nutrient content were harvested equally among treatments within season. Seed of high lipid content was harvested significantly more in the fall than spring. Bouteloua curpendula, a late-successional mid-grass, was harvested significantly more in the spring than the fall. Foragers selected seed species proportional to their abundance in the community, with selection expressed only among numerically rarer species. These results support the hypothesis that some species are preferred depending upon season. Preferences for native seed, both within and among seasons, depend on the grazing treatment. Contrary to many studies forb seeds are selected as much as grass seeds.
Key words: granivory, grasslands, Pogonomyrmex barbatus, seed preferences