Talon Stammen

Date of Award

January 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Robert A. Newman

Abstract

Boreal wetlands are ecologically rich yet vulnerable ecosystems shaped by hydrological dynamics, cold climate regimes, and landscape-scale disturbances. Among the most influential agents of change in these systems are beavers (Castor canadensis), whose engineering activities create a mosaic of lentic habitats at varying stages of ecological succession. This dissertation investigates the structure and dynamics of amphibian and aquatic macroinvertebrate communities across a beaver-influenced wetland landscape in Voyageurs National Park, Minnesota, USA.The first study (Chapter II) examines breeding phenology and detection patterns of boreal anurans using a combination of passive acoustic monitoring and visual encounter surveys at 25 wetlands over four years (2019–2022). Distinct seasonal calling patterns and developmental phenology were documented for seven species, revealing interspecific differences in timing and detectability. These patterns underscore the importance of time-sensitive monitoring protocols in temperate amphibian research and conservation.

The second study (Chapter III) models amphibian occupancy as a function of wetland successional stage, pond size, and spatial location using site-level ecological predictors across 55 wetlands (35 sites in multi-year analyses) over four years. Species-specific logistic regression models revealed that habitat suitability was high across successional stages and wetland perimeter was among the most influential factors structuring occupancy, though spatial patterns were limited at the scale of the study. The presence of metamorphs and juveniles confirmed successful breeding at many sites and provided supporting evidence for site-level habitat suitability.

The third study (Chapter IV) evaluates aquatic macroinvertebrate diversity and community composition in relation to successional stage, wetland type, and year across the same sites and time period as the amphibian component. Mid-season dip net sampling and laboratory identification to family level revealed high invertebrate richness across sites, with richness patterns corresponding to habitat structure and successional stage. Ordination analyses highlighted variation in assemblage structure associated with beaver-driven environmental heterogeneity and wetland classification.

Together, these studies offer a comprehensive ecological portrait of boreal wetland communities and their response to a natural gradient of habitat succession shaped by beaver activity. The work integrates species phenology, spatial habitat modeling, and community ecology within a landscape framework. It contributes critical baseline knowledge of amphibian and invertebrate biodiversity in a northern protected area, informs wetland management strategies, and illustrates the ecological value of long-term, multi-taxa monitoring in dynamic ecosystems.

Download

Share

COinS