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Item Environmental drivers of bee community diversity in Yellowstone National Park(Montana State University - Bozeman, College of Letters & Science, 2022) Switzer, Kristen Ann; Chairperson, Graduate Committee: Laura BurklePollinators are essential to their ecosystems and facing large declines. Studies on environmental drivers of bee community composition are currently lacking in North America, particularly in national parks. Understanding how bee diversity and plant-bee interactions change across environmental gradients gives us insight into the resilience of bee communities in the future. We collected data at seven sites across an elevational gradient in Yellowstone National Park. Pan traps were used to collect bee diversity data from in 2010, 2011, 2012, and 2020, and hand-netting was used to collect plant-bee interaction data from June to August 2020. We hypothesized that elevation would be a major driver of bee abundance, species richness, and community composition and that bee diversity would decrease as elevation increased. We predicted bee diversity would peak in the middle of the growing season in response to floral diversity peaking at that time. Finally, we predicted plant-bee interactions would be more generalized at higher elevations and flower species richness would be a major driver of network specialization (H2'). Our results revealed that seasonality and elevation were major drivers of bee abundance and species richness, indicating that both spatial and temporal factors are important in driving bee community patterns. Bee species richness was highest in 2010 and declined over years, which may signal that changing environmental conditions are stressing bee communities. Bee abundance and species richness declined as each growing season progressed, which aligns with broader literature on various taxa and mirrors seasonal flower diversity patterns. Despite close alignment between bee and floral diversity patterns, flower species richness was only a significant driver of bee community composition, indicating that other environmental gradients were bigger drivers of bee abundance and species richness patterns. Bee species richness was a significant driver of plant-bee network specialization and elevation, slope, and flower species richness were marginally significant, suggesting that plant- bee interactions are influenced more by spatial than temporal variables. Additional studies focusing on bee diversity across growing seasons and years could provide insights into how changing environmental conditions in the future may influence bee diversity and community resilience in Yellowstone National Park.Item Macroinvertebrate diversity, community structure, and dispersal are affected by tributary identity and confluence conditions in a regulated river(Montana State University - Bozeman, College of Letters & Science, 2023) Maguire, Zachary John; Chairperson, Graduate Committee: Lindsey Albertson; This is a manuscript style paper that includes co-authored chapters.Tributaries are essential components of freshwater ecosystems, playing a crucial role in maintaining connectivity and providing habitat for a diverse array of aquatic organisms. The role of tributaries in creating heterogeneity in physical conditions and food resources for fishes could be critical, yet little is known about how variable conditions in different tributaries in regulated river systems influence the mainstem. Using field observations in five tributaries on the Madison River, Montana, we found that tributaries in the same network and within relatively short distances of 60km varied greatly in their environmental conditions, macroinvertebrate densities, and macroinvertebrate community structure. Downstream of confluences macroinvertebrate richness increased overall, and per capita weight of drifting macroinvertebrates decreased overall. These findings suggest that confluences may act as hotspots for biodiversity in regulated rivers and introduce smaller bodied macroinvertebrates to the drift. The amount that a tributary influenced benthic richness and mean per capita weight in the drift downstream of its confluence was related to land use and abiotic factors within that tributary; both macroinvertebrate metrics significantly increased in magnitude downstream of confluences with higher percentage of US Forest Service land, cooler temperatures, decreased discharge, and increased elevation loss (i.e. steeper watershed slope). In contrast, tributaries that had a larger proportion of agricultural land, warmer temperatures, and higher discharge more strongly influenced benthic macroinvertebrate metrics. These tributaries supported higher benthic density and biomass downstream of confluences. Our results offer insight into the ways that tributaries can create heterogeneous habitats that in turn structure macroinvertebrate communities in mainstem rivers and suggest that conservation and restoration of these essential components of freshwater ecosystems is a well-spent endeavor in rivers with regulated mainstems. Future research will need to test the ubiquity of the patterns we observed in other river networks and under other global changes such as pollution, invasive species, and drought. Continued understanding of the importance of heterogeneity imparted by tributaries and their confluences on diversity, availability, and quality of food for threaten fishes is needed to guide restoration efforts aimed at improving river condition and resilience.Item Fish assemblage response to habitat restoration in Elk Springs Creek, Montana: implications for arctic grayling (Thymallus arcticus) restoration(Montana State University - Bozeman, College of Letters & Science, 2021) Marsh, Jason William; Chairperson, Graduate Committee: Alexander V. ZaleThe abundance and distribution of Arctic Grayling Thymallus arcticus in Montana have declined substantially during the past century as a result of habitat degradation and loss. Biologists tasked with conserving Arctic Grayling populations in the Centennial Valley of southwestern Montana implemented two habitat restoration projects to reclaim historical Arctic Grayling migration corridors and spawning habitats in Elk Springs Creek. I used before-after and before-after control-impact (BACI) study designs to evaluate the effects of these habitat restoration projects on physical habitat, water quality, and Arctic Grayling in Elk Springs and Picnic creeks. Because Arctic Grayling were rare in Elk Springs and Picnic creeks, I also examined the effects of restoration on two additional species (Brook Trout Salvelinus fontinalis and White Suckers Catostomus commersonii) with habitat requirements and life history characteristics similar to those of Arctic Grayling. I used electrofishing to monitor the abundance, biomass, and size distribution of each species before the restoration in 2016, and after the restoration during 2017 and 2018. A PIT-tag detection network monitored the seasonal movements of Arctic Grayling, Brook Trout, and White Suckers from spring 2016 through autumn 2018. In situ data loggers measured summer stream temperatures and dissolved oxygen concentration in expected fish migration corridors both before and after restoration. The abundances and biomasses of Arctic Grayling and White Suckers were similar before and after restoration. However, Brook Trout abundance and biomass increased significantly in the restored (impacted) reaches relative to the unrestored (control) reaches two years after habitat restoration. The size-class distributions of Arctic Grayling and Brook Trout broadened after restoration. Movements of Arctic Grayling, Brook Trout, and White Suckers among unique habitat segments in Elk Springs and Picnic creeks increased after restoration, but pre-restoration movement data was sparse and limited inference. Following channel restoration, summer stream temperatures decreased, and dissolved oxygen concentration increased and equilibrated. Physical habitat improved (i.e., fine sediments decreased, and depth, percentage of pools, and gravels increased) in restored historical Arctic Grayling spawning areas. I thereby showed that channel reconnection and spawning habitat restoration can substantially improve water quality and physical habitat. However, the restoration measures implemented in Elk Springs Creek affected my target species disproportionately.Item Understanding the effects of wildfire on the functional traits of plants and bees(Montana State University - Bozeman, College of Letters & Science, 2018) Durney, Janice Simone; Chairperson, Graduate Committee: Laura BurkleDiversity, often assessed by species richness, fosters ecosystem success, promoting ecosystem services, stability, and adaptation. Evaluations of functional trait composition are a better indicator of ecological process dynamics. Functional trait variation of species within a community (i.e., inter-specific variation) and of individuals within a species (i.e., intra-specific variation) may reflect adaptations and phenotypic variation contributing to the functional diversity of a community in the face of change. Wildfires have shifted from mixed-severity to frequent high-severity fires, due to fire suppression and climate change, modifying ecosystem function, trait selection pressure, and species sorting. Traits involved in plant-pollinator interactions can be used to understand the mechanisms underlying shifting interactions across communities and how post-wildfire environmental conditions affect community assembly, structure, and stability. We tested how productivity, time-since-burn, and wildfire severity influenced mean functional trait values and inter- and intra-specific functional trait variation of plants and bees known to interact in southwestern Montana, USA. Fieldwork was conducted from 2013-2017 in two locations that differed in productivity with similar fire histories of recent-mixed-severity, recent-high-severity, older-high-severity burns, and unburned areas. Functional traits involved in plant-bee interactions were selected and measured among plant and bee species observed across these various productivity, time-since-burn, and fire severity levels. We found that as productivity and time-since-burn increased, the mean functional trait values and inter- and intra-specific functional trait variation of plants and bees increased. In addition, productivity, time-since-burn, and fire severity affected the functional trait values and variation of plant species more than bee species. These results suggest that as productivity and time-since-burn increases so does trait diversity - promoting ecosystem function and stability. The increased effect of productivity and time-since-burn on plant functional traits compared to bee traits suggests the dispersal abilities of bees allow them to cope with the effects of fire, while plant species are more prone to productivity and time-since-burn habitat filtering and species sorting, potentially due to limited mobility. Our results support previous findings that shifting wildfire regimes from mixed to high-severity burns increases species sorting and limits trait variation after wildfire regardless of productivity but trait variation increases as time-since-burn and productivity increases.Item Interaction turnover among pollination networks across space, time, and environment(Montana State University - Bozeman, College of Letters & Science, 2013) Simanonok, Michael Peter; Chairperson, Graduate Committee: Laura BurklePollination networks provide an ideal system in which to test hypotheses around interaction turnover across ecologically meaningful gradients, as there is already baseline understanding of plant and pollinator communities. Parallel declines in plants and pollinators imply that disruption of interactions between species in pollination networks may be leading to pollinator declines; therefore, beginning to understand how plant-pollinator interactions turnover through space, time, and environment could be vital for future conservation and management efforts. I investigated i.) how do plant and pollinator species diversity (i.e., richness and evenness), phenology, and composition change across space, time, and environment, ii.) how do interactions between pollination networks turn over across these same gradients (i.e., space, time, and environment), and iii.) what is the relative contribution of species turnover (plant, pollinator, or both simultaneously) vs. host switching to interaction turnover among pollination networks? Field work was conducted during summer 2012 on the Beartooth Plateau, an alpine ecosystem in Montana and Wyoming, with weekly observations of plant-pollinator interactions and the floral community across the growing season. Community diversity and composition were compared across space, time, elevation, slope, and aspect using linear regressions, t-tests, and principle coordinate analysis. Interaction turnover was calculated between all possible pair wise combinations of study site and week and compared across, space, time, elevation, slope, and aspect using a partial Mantel test and linear regressions. We found that interaction turnover mostly occurred due to simultaneous species turnover of both plant and pollinator communities with host-switching having marginal contribution. Furthermore, interaction turnover occurred across temporal and environmental gradients, with no significant variation across spatial scales. These results differ greatly from inter-annual patterns on the contribution of species turnover vs. host switching, however some results may be due to sampling or scale limitations. It is possible that host switching does not readily occur within-season, but more work is needed for confirmation. Spatial and environmental patterns remain possible, but did not emerge at the extents used herein. This study represents the first instance of the partitioning of interaction turnover into individual species components for a pollination network, and the first to do so intra-annually.Item Bird response to landscape pattern and disturbance across productivity gradients in forests of the Pacific Northwest(Montana State University - Bozeman, College of Letters & Science, 2007) McWethy, David Burch; Chairperson, Graduate Committee: Andrew HansenManaging forest lands for biodiversity is a common goal in the public and private forests of the Pacific Northwest and is typically achieved through harvests that result in an array of vegetation structural conditions that provide suitable habitat for a number of species. The assumption is made that the causative factors of biodiversity do not vary geographically and that silviculture, as a management tool, can be applied similarly across different biophysical locales. The primary aim of this research is to better understand how species respond to both local and landscape-scale forest structural conditions in landscapes with different levels of productivity (e.g. gross primary productivity). We hypothesized that the influence of landscape effects on bird richness, abundance and community organization would be more pronounced in highly productive environments. We also hypothesized that species response to disturbance would differ across gradients in ecosystem productivity. We predicted that bird diversity would increase with increasing disturbance extent where favorable climatic conditions result in high levels of competitive exclusion. Alternatively, we predicted that bird diversity would decrease with increasing disturbance extent when factors other than competition limit or regulate bird species diversity.Item Biodiversity potential in the Pacific and Inland Northwest : the relative importance of forest structure and available energy in driving species diversity(Montana State University - Bozeman, College of Letters & Science, 2007) Verschuyl, Jacob Pieter; Chairperson, Graduate Committee: Andrew J. HansenCurrently, the most common strategy of forest biodiversity managers in the Pacific and Inland Northwest (PINW) is to maintain structural complexity within forest stands and create the full range of seral stages across the landscape. Recent advances in ecological theory reveal that biodiversity at regional to continental scales is strongly influenced by available energy (i.e. factors influencing vegetative growth such as precipitation, temperature, radiation, soil fertility). We hypothesized bird species richness (BSR) exhibits a positive or unimodal relationship with energy across landscapes and the relationship between energy and BSR within a landscape is positive in energy limited landscapes and flat or decreasing in energy rich landscapes. Additionally, we hypothesized that structural complexity explains a lower percentage of the variation in BSR in energy limited environments and higher percentage in energy rich environments and that the slope of the relationship between structural complexity and BSR is greatest in energy rich environments.