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The Spatial Ecology Of The Comanche Harvester Ant, Pogonomyrmex comanche (Hymenoptera: Formicidae)
Mayo, Ann Burgess
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Because of the diverse roles ants play, it has been suggested that ants may be ecosystem engineers and so, may be useful in monitoring ecosystem function and health. Because ant activities are localized around their nests, ant colony spatial patterns may have important ecological impacts on their own populations, other organisms and the environment. While some species in the harvester ant genus Pogonomyrmex are well studied, little is known about the Comanche harvester ant, Pogonomyrmex comanche.The goal of this study was to characterize the spatial pattern of local populations of P. comanche and investigate possible influences on this pattern. The examination of its local distribution and factors that influence that distribution may contribute to understanding P.comanche biogeography, population biology, ecological relationships and because of their movement between prairie and wooded habitats, may contribute to understanding some of the ecosystem processes important in the Cross Timbers Ecoregion.I hypothesized that the spatial pattern of P. comanche colonies is regular. Such a pattern implies the influence of competition and aggression among colonies as a driving force for population organization. I further hypothesized that the important influences on this spatial pattern include habitat characteristics, the presence of other ant species and colony interactions involving nestmate discrimination via aggression.I assessed the colony spatial pattern by mapping colonies in five areas from 2009 – 2013 and analyzing the pattern with a spatial point process, Ripley’s K function. To investigate habitat characteristics and other ant species, I assessed the ground active ant assemblage and environmental variables in 21 sites. I collected ants with pitfall traps in June, July, and August 2012 and measured environmental variables when the ants were collected. I calculated several diversity indices and used a redundancy analysis (RDA) to assess the differences in ant species among sites and ant response to environmental variables. Finally, I used a behavioral assay to test P. comanche’s ability to discern nestmates from non-nestmates in order to investigate aggression as a factor influencing the colony spatial pattern.I found that P. comanche colonies are randomly distributed at spatial scales up to 50 m, the ant assemblage differs among sites, species diversity is higher in prairie habitats compared to wooded habitats and P. comanche does discriminate nestmates from non-nestmates. However, I found no evidence that aggression is a significant factor in colony location or spatial pattern.