Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type


Type of Thesis

Departmental Honors


Ecology and Evolutionary Biology

First Advisor

Dr. Michael Breed

Second Advisor

Dr. Pieter Johnson

Third Advisor

Dr. Sarah Massey-Warren


Ants are widely regarded as ‘ecosystem engineers’ because they change the biological, chemical, and physical properties of the soil around their nests through nest construction and contributions to nutrient cycling. These processes were investigated in a species of alpine ant, Formica podzolica, to quantify its effects on soil structure and vegetation composition in an alpine ecosystem in Nederland, Colorado. Measurements of vegetation percent cover, biomass, species diversity and abundance, soil moisture and pH, and 15N in plants were taken at various distances from nests. A stable isotope analysis was utilized to determine the amount of 15N in vegetation surrounding nests, which provides information on the relatedness of ants and vegetation in a trophic web. Results showed that proximity to a nest had a positive influence on plant abundance and soil moisture. Additionally, high plant 15N concentrations near nests, compared to control sites (away from nests), aligned with high 15N in ant samples. F. podzolica has relatively large-scale impacts on the alpine ecosystem surrounding their nests. This research reveals how the daily foraging and excavation activities of an ant colony can lead to long-term changes in soil and vegetation structure, and suggests that F. podzolica ants are having similar ecosystem effects across North America.