Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Pollinator conservation and restoration in semi-natural ecosystems(Montana State University - Bozeman, College of Letters & Science, 2022) Glenny, William Robb; Chairperson, Graduate Committee: Laura Burkle; This is a manuscript style paper that includes co-authored chapters.Semi-natural ecosystems are areas with biological and physical characteristics that resemble natural ecosystems but are also affected by anthropogenic disturbances. Semi-natural ecosystems are also areas with high insect pollinator diversity. Land management actions within semi-natural ecosystems may therefore be important to counteract future declines of insect pollinators. However, current restoration strategies for insect pollinator communities are based on evidence from agricultural ecosystems, which have frequent human interventions to ensure plant success, neglect the importance of nesting materials, and primarily benefit generalist species. To inform management actions for the conservation and restoration of insect pollinators in semi- natural ecosystems, I (1) synthesized the current understanding of the effects of common land management actions on insect pollinators on public lands in the US, (2) identified habitat characteristics which structure the taxonomic and functional diversity of bee communities, (3) evaluated the strength of influence of mechanisms associated with diet breadth across groups of bee species and (4) designed a conceptual model which can be used to select flowering plant species to provide food resources for bee communities in semi-natural ecosystems. Management actions that increase the abundance of floral and nesting resources to support bee species from different functional groups are required to conserve and restore insect pollinator communities in semi-natural ecosystems. I found that (1) management actions have positive, neutral, and negative effects on insect pollinators, but research trends vary depending on the taxon and habitat type, (2) the taxonomic and functional diversity of bee communities are structured by the abundance of both floral and nesting resources, (3) patterns of abundance across space and time have a more positive effect on the diet breadth of bumble bee species compared to non- bumble bee species, and (4) wildflower species that receive a high visitation rate and richness, occupy functionally important positions within bee-flower interaction networks, and are spatially and temporally widespread are important to provide bee communities with food resources in semi-natural ecosystems. These wildflower species may be particularly important to include within seed mixes to revegetate semi-natural ecosystems and provide food resources for insect pollinators.Item Bee and butterfly communities in roadside habitats: identifying patterns, protecting monarchs, and informing management(Montana State University - Bozeman, College of Letters & Science, 2023) Meinzen, Thomas Claasen; Chairperson, Graduate Committee: Diane M. DebinskiInsect pollinators play a critical role in our natural and agricultural ecosystems. With global pollinator declines and habitat loss, attention has turned to roadside right-of-way lands (ROWs) as potential areas for supporting pollinator populations. Although many roadsides host flowering plants, understanding whether--and under what circumstances--roadsides actually benefit pollinator populations is critical for good conservation decision-making. Through a literature review, we found that pollinator population data (e.g., birth and death rates) are lacking to assess whether roadsides are a source or sink for pollinator populations. However, conscientious management practices, including reduced, well-timed mowing, selective, targeted spraying, and well-placed native plantings can improve roadsides' potential to support robust pollinator populations. Identifying roadside habitat for diverse pollinator communities and imperiled species is essential to prioritize pollinator-focused management practices across ROW systems. To support efforts to conserve monarch butterflies (Danaus plexippus), we surveyed 1,465 km (910 miles) of southern Idaho highways, mapping 1,363 patches of showy milkweed (Asclepias speciosa), the monarch's host plant. Roadside milkweed often bordered irrigated fields and crops; water availability may best explain its distribution. Existing statewide milkweed models (Svancara et al., 2019) did not effectively predict milkweed distribution in ROWs, suggesting the importance of roadside-specific factors, such as ROW management and disturbance history. To identify patterns of pollinator richness and abundance in Idaho ROWs, we surveyed butterflies and sampled bees at a randomized set of 63 100-meter (328-foot) roadside transects in southeastern Idaho, stratified by highway class and NDVI (greenness) category. Lower NDVI (less green) sites, those with more flowering plant species, and sites along smaller, less-trafficked highways supported significantly more species of bees, while ROWs with more abundant flowers were associated with more species of butterflies. Low NDVI sites were often characterized by native sagebrush plant communities, while sites of high NDVI were associated with high proportions of non-native plants, suggesting that NDVI might be useful both in predicting bee richness and abundance (low values) and locating developing noxious weed patches (high values). These results, together with our management recommendations, can help prioritize ROWs for pollinator protection and increase their capacity to support diverse pollinator communities.Item Plant-pollinator network assembly after wildfire(Montana State University - Bozeman, College of Letters & Science, 2018) Simanonok, Michael Peter; Chairperson, Graduate Committee: Laura BurklePlant-pollinator networks are threatened by anthropogenic influence due to habitat loss, changing fire regimes, climate change and other factors. Furthermore, we have little current knowledge for how species interactions and processes like pollination assemble and recover post-disturbance. Studying the mechanisms by which plant-pollinator interactions assemble in a post-disturbance landscape, particularly across gradients of disturbance intensity and successional time, would greatly help in building foundational ecological knowledge regarding the assembly of species interactions as well as provide specific information to aid conservation and management. Therefore, we investigated plant-pollinator network assembly after wildfire, between mixed- and high-severity burns and across time-since-burn, and we asked i) how do network structure and the network roles of persistent species vary ii) how does wildfire change the nutritional landscape of available floral pollen quality and how does that influence bumble bee foraging and nutrition, and iii) how do nesting and floral resources affected by wildfire influence wood-cavity-bee nesting success and richness? Our study design involved four wildfires from the Absaroka Mountains of southwest Montana, USA, which included a range of burn severities as well as a 1-25 year chronosequence of time-since-burn sampled primarily from 2014 to 2016. Bees were sampled via hand netting and nesting boxes alongside floral census transects and pollen sampling to assess metrics important to plant-pollinator network assembly, available floral pollen quality, bumble bee nutrition, and wood-cavity-nesting bee nesting success. The primary findings are that i) plant-pollinator network structure does not dramatically shift with burn severity or time-since-burn, nor do the network roles of persistent species, ii) available floral pollen quality and bumblebee nutrition are limited by high-severity burns, and iii) burn severity has little effect on the nesting success of wood-cavity-nesting bees. The conclusions that follow these results are mainly that i) evidence of constant structure and low variance of species' roles provides evidence for preferential attachment over opportunistic attachment in assembling plant-pollinator networks post-disturbance, ii) varied species composition between mixed- and high-severity burns may mean that bumble bees are nutritionally limited in high-severity burns, and iii) nesting resources do not appear to strongly limit nesting success or richness of wood-cavity-nesting bees.Item The influence of post-wildfire logging on forb and pollinator communities and forb reproductive sucess, Gallatin National Forest, Montana(Montana State University - Bozeman, College of Letters & Science, 2016) Heil, Laura Jean; Chairperson, Graduate Committee: Laura BurklePollinators are in decline worldwide, and these declines have implications for flowering plants and their reproduction, given that 80% of flowering plants depend on insects for pollination. One potential contributor to pollinator species' declines is shifts in disturbance regimes, such as increased severity and frequency. Wildfires are essential natural disturbances that are important drivers of forest biodiversity in the western U.S., and there is often pressure to respond to wildfire with management including post-wildfire logging. This management strategy involves the removal of dead trees for economic value immediately following wildfire. Thus, is expected that post-wildfire logging has additional impacts on forest communities compared to non-salvage logging, and that it impacts forb and pollinator communities. Several studies have examined the short-term responses of forb and pollinator communities to wildfire and non-salvage logging individually, and one study examined their combined effects. However, no studies have examined the long-term effects of post-wildfire logging, on forb and pollinator communities and on forb reproduction. My research addresses these gaps in knowledge and asks: 1) how do floral and bee communities respond to post-wildfire logging and how do their responses differ between two different-aged fires, and 2) how does post-wildfire logging influence forb reproduction and pollen limitation of reproduction in an older wildfire? In the more recent fire, floral and bee density and species richness were higher in logged than unlogged areas. By contrast, in the older fire, forb and bee communities were similar between logged and unlogged areas. Unexpectedly, we found large inter- and intra-annual variation in the effects of post-wildfire logging. Lastly, in the older fire, there were no effects of post-wildfire logging on forb reproduction, but plants were pollen limited in unlogged areas. This suggests that plants in unlogged areas are able to augment their reproductive output with supplemental pollen resources, but plants in logged areas cannot. Together, these results suggest that post-wildfire logging is beneficial for forbs and pollinators in the short-term, and these positive effects depend on time of growing season and sampling year. However, post-wildfire logging may be detrimental for forb reproduction in the long-term.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.