UC Riverside

Organisms exhibit characteristics that can change depending on the environment and vary across a species, especially those with expansive ranges. Due to eusociality, which has led to proliferation throughout nearly every terrestrial ecosystem, many social insects make ideal subjects for studying variation in how a species interacts with the environment across its range. Soil-dwelling ants create and modify habitat as ecosystem engineers while building nests that act as an extended phenotype, buffering the colony against climate. Understanding how ants can persist in a wide range of environments and developing a predictive understanding of their soil impacts across environmental gradients will advance our knowledge of soil ecosystem function. Through soil sampling in and around nests and a controlled laboratory experiment, I investigated the extent to which climate influences nest architecture and the effects of nests on soil properties. Additionally, I conducted genomic analyses to identify markers associated with climatic heterogeneity in a widespread species, Formica podzolica. I found that nests differentially affect soil chemistry across elevational gradients; at lower elevations, nest soil had lower amounts of carbon and nitrogen than control soil, but at higher elevations, the opposite pattern was present. Nest architecture is shaped by local adaptation and a plastic response to temperature; while workers experiencing a high temperature excavated deeper nests than those experiencing a cooler temperature, I observed a significant interaction effect of natal elevation and temperature treatment on nest size and complexity. While these traits are plastic, genomic underpinnings may also influence ants’ fitness and their impact on soil in different climates; genomic signatures of adaptation to temperature, precipitation, and seasonality were present across F. podzolica’s range, with one locus exhibiting a precipitation-associated alternative allele exclusively at the northern edge of the range. Combined, these studies suggest that Formica ants likely modulate soil properties differently across environmental gradients, their nests are shaped by a combination of plastic and locally adapted behaviors, and genomic variation may be a factor in adaptive potential, especially at range margins.