Ecological effects of seed harvesting ants on rangeland plant communities

Uhey, Derek Andrew (2022) Ecological effects of seed harvesting ants on rangeland plant communities. Doctoral thesis, Northern Arizona University.

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Abstract

Harvester ants play important ecological roles through nest construction and trophic interactions, considered by many to be keystone species. Yet they have historically been labeled as pests and persecuted within their native ranges. This dissertation focuses on understanding beneficial and detrimental roles of harvester ants to human activities and rangeland ecosystems. I review the literature focusing on support or lack of support for keystone and pest effects of harvester ants in rangeland habitat. Harvester ants perform beneficial roles such as: a) nest rims serving as refugia for plants thereby increasing ecosystem stability, b) the dispersal or consumption of seeds, and c) trophic roles such as predation of arthropod and prey to insectivores. Oppositely most detrimental roles had little to no scientific support, instead stemming from anecdotes or assumption. The only detrimental role that potentially justifies eradication of harvester ants in rare cases is the powerful sting of some species. However, other roles of harvester ants are recently discovered and require more study to clarify the beneficial or detrimental effects to human activities. I investigated the roles of harvester ants in structuring vegetation through nest-construction and seed harvesting. Harvester ants enhanced both native and invasive plant species along their nest rims. Harvester ants preferred a variety of native grass seeds but rejected seeds from other species. These findings are important for broadcast seeding and invasion dynamics in areas with high densities of harvester ants. Harvester ants have been accused of causing degradation because their nest densities may be increased from disturbances such as grazing, although in these cases they are a symptom not cause of ecosystem disfunction. I investigated how human activities change harvester ant nesting densities. The presence of hiking trails increased nest densities, while grazing decreased them. These results underscore the roles human activities have in either promoting or decreasing abundances of ants. Overall, the few detrimental roles of harvester ants seem easily mitigated and none support persecution of harvester ants as pests, while the strong support for their roles as keystone species indicate the importance of their conservation.

Item Type:	Thesis (Doctoral)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Disturbance; Granivory; Keystone species; Pogonomyrmex; Productivity; Rangeland; Harvester ants;
Subjects:	Q Science > QL Zoology
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of the Environment, Forestry, and Natural Sciences > School of Forestry
Date Deposited:	01 Jun 2023 16:49
Last Modified:	01 Jun 2023 16:49
URI:	https://openknowledge.nau.edu/id/eprint/5938

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