Abstract
Harvester ants have long been known to exhibit interspecific seed preference and this preference has been thought to be associated with distance in a manner analogous with optimal foraging theory. However, little attention has been given to how intraspecific seed preference changes or how microhabitat (i.e. the composition of the terrain that the ants are moving through) impacts seed harvesting preference. We addressed these questions by conducting seed harvesting experiments in three different Ephedra viridis populations that contain harvester ants (Pogonomyrmex occidentalis) by using only E. viridis seeds and conducting trials over multiple distances and varying degrees of microhabitat cover. We found that increased microhabitat cover and increased seed mass decrease the likelihood of E. viridis seeds being harvested much more dramatically than distance. However, we found no effect of distance or microhabitat cover on which E. viridis seeds were harvested. We conclude that harvester ant E. viridis seed preference is distance and microhabitat independent. However, increases in microhabitat cover negatively impacts the likelihood of P. occidentalis harvesting E. viridis seeds of any size. Our findings suggest that harvester ant foraging behavior is influenced by structure of the microhabitat more than by distance. This provides a new context on how harvester ant foraging behavior and effectiveness should be considered.
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Acknowledgments
We would like to thank the University of Nevada, Reno for providing us with the opportunity to conduct this research. We would like to thank all the undergraduate lab assistants who helped weigh and measure all of the seeds in this experiment. We would also like to thank the reviewers who provided valuable feedback in improving the quality of this manuscript. Lastly, we would like to thank all of the individuals at the University of Nevada, Reno who provided valuable feedback during the development of this project. This work was supported by the National Science Foundation GK-12 Program, Grant DGE No. 1045584 [AH]. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation; This was supported by the University of Nevada, Reno Ecology, Evolution, and Conservation Biology department summer research grant [AH].
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Hickey, A., Hollander, J. & Peacock, M. Assessing Microhabitat Cover and Distance Effects on Harvester Ant Intraspecific Seed Preference. J Insect Behav 29, 535–547 (2016). https://doi.org/10.1007/s10905-016-9580-2
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DOI: https://doi.org/10.1007/s10905-016-9580-2