Biology Ph.D. Dissertations

The Effect of Anthropogenic Habitat Modification on Insect-Mediated Ecosystem Services

Date of Award

2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Biological Sciences

First Advisor

Shannon L. Pelini (Advisor)

Second Advisor

Nathan Hensley (Other)

Third Advisor

Kevin McCluney (Committee Member)

Fourth Advisor

Karen V. Root (Committee Member)

Fifth Advisor

Michael Weintraub (Committee Member)

Abstract

Human activity and land use negatively affect many arthropods that provide important ecosystem services. Agricultural land and cities are both common types of human-modified habitat that often have decreased arthropod richness and diversity, due in part to loss of habitat quantity, habitat complexity (i.e. habitat types available), and structural complexity (i.e. habitat density, shape, or height). This dissertation focuses on gaps in understanding of the relationship between habitat complexity and arthropod-mediated ecosystem services in human-modified environments. In agricultural fields, we examined the response of ground arthropods, microbial activity, and nutrient pools to applications of a nutrient source (labile detritus: mayfly carcasses) and/or habitat structure (recalcitrant detritus: corn stover) over a 7-week period. In urban prairies, we examined the relationship between arthropod predators and complexity, and the impact that urban features have on that relationship at multiple scales. Throughout the work presented in this dissertation, we found that known patterns and relationships were disrupted or dampened in human-modified habitats. Though labile detritus recruited ground arthropods to agricultural fields, they did not stimulate nutrient cycling as they do in less-modified systems. The labile detritus provided nutrients but had little impact on microbial activity. These findings suggest that low baseline biotic activity in agricultural fields lessens our ability to promote biotic nutrient cycling. In urban prairies, we found that on a small-scale, predator-prey ratio increased with structural complexity, but only structural complexity at lower heights and when the structural complexity was primarily due to forbs. On a larger scale, arthropod abundance and predation were best predicted by complexity within prairies, while arthropod community structure was best predicted by habitat complexity and urban features surrounding a prairie. Taken together, these findings suggest that in urban prairies, the surrounding complexity may determine which arthropods can find and/or persist in a prairie, while complexity within the prairie determines how many of the arthropods can be supported and perhaps even the ecosystem services they provide, once in the prairie. Ultimately, this dissertation fills gaps in the literature regarding the impact of habitat and structural complexity on arthropod ecosystem services in human-modified environments.

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