Publications by Colleges and Departments (MSU - Bozeman)
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Item Dynamics of a plant–pollinator network: extending the Bianconi–Barabási model(Springer Science and Business Media LLC, 2024-06) Castillo, William J.; Burkle, Laura A.; Dormann, Carsten F.We study the dynamical assembly of weighted bipartite networks to understand the hidden mechanisms of pollination, expanding the Bianconi–Barabási model where nodes have intrinsic properties. Allowing for a non-linear interaction rate, which represents the seasonality of flowers and pollinators, our analysis reveals similarity of this extended Bianconi–Barabási model with field observations. While our current approach may not fully account for the diverse range of interaction accretion slopes observed in the real world, we regard it as an important step towards enriching theoretical models with biological realism.Item Seasonality and alternative floral resources affect reproductive success of the alfalfa leafcutting bee, Megachile rotundata(Taylor & Francis, 2024-08) Delphia, Casey M.; Burkle, Laura A.; Botti-Anderson, Joshua M.; O'Neill, Kevin M.Background: Managed populations of the alfalfa leafcutting bee (ALCB), Megachile rotundata (F.), are often not sustainable. In addition to numerous mortality factors that contribute to this, the dense bee populations used to maximize alfalfa pollination quickly deplete floral resources available to bees later in the summer. Providing alternative floral resources as alfalfa declines may help to improve ALCB reproduction. Methods: We examined the relationship between floral resource availability and ALCB reproduction and offspring condition via (1) a field study using alfalfa plots with and without late-blooming wildflower strips to supply food beyond alfalfa bloom, and (2) a field-cage study in which we provided bees with alfalfa, wildflowers, or both as food resources. Results: In the field study, bee cell production closely followed alfalfa floral density with an initial peak followed by large declines prior to wildflower bloom. Few bees visited wildflower strips, whose presence or absence was not associated with any measure of bee reproduction. However, we found that female offspring from cells provisioned earlier in the season, when alfalfa predominated as a source of provisions, eclosed with greater body sizes and proportion body lipids relative to total body mass. For bees restricted to cages, the proportion of offspring that survived to adults was highest on pure alfalfa diets. Adding wildflowers to cages with alfalfa did not affect adult offspring production or female offspring body size and lipid content. Furthermore, although similar numbers of adults were produced on wildflowers alone as with alfalfa alone, females eclosed with smaller body sizes and lower proportion body lipids on wildflowers despite the higher protein content we estimated for wildflower pollen. We found no evidence that adding the late-season wildflower species that we chose to plant enhanced ALCB offspring numbers. Our results highlight the importance of considering multiple measures of reproductive success, including offspring body size and lipid stores, when designing and evaluating floral resource management strategies for agroecosystems.Item Dynamics of a plant–pollinator network: extending the Bianconi–Barabási model(Springer Science and Business Media LLC, 2024-06) Castillo, William J.; Burkle, Laura A.; Dormann, Carsten F.We study the dynamical assembly of weighted bipartite networks to understand the hidden mechanisms of pollination, expanding the Bianconi–Barabási model where nodes have intrinsic properties. Allowing for a non-linear interaction rate, which represents the seasonality of flowers and pollinators, our analysis reveals similarity of this extended Bianconi–Barabási model with field observations. While our current approach may not fully account for the diverse range of interaction accretion slopes observed in the real world, we regard it as an important step towards enriching theoretical models with biological realism.Item Bees and Butterflies in Roadside Habitats: Identifying Patterns, Protecting Monarchs, and Informing Management(ITD Reseach Program, 2023-07) Meinzen, Thomas C.; Debinski, Diane M.; Burkle, Laura A.; Ament, Robert J.Pollinating insects provide vital ecosystem services and are facing global declines and habitat loss . Roadsides are increasingly regarded as important potential areas f or enhancing pollinator habitat. Understanding which roadsides best support pollinators — and why — is essential to helping locate and prioritize pollinator conservation efforts across roadside networks. To support this effort, we assessed butterfly, bee, and flowering plant species richness and abundance on a set of 63 stratified randomized roadside transects in State-managed rights-of-way in SE Idaho. Our research evaluated pollinator diversity as a function of highway class (interstate, U.S., and state highways), remotely sensed NDVI values (a measure of vegetation greenness), and floral resources. We found that smaller highways and lower (less green) maximum NDVI values were associated with significantly more bee species and total bees. Roadsides bordering sagebrush habitats typically had low NDVI values and higher bee and butterfly species richness, potentially contributing to this observed pattern. Butterfly richness increased in association with higher floral abundance in roadsides. Additionally, we identified and mapped 1,363 roadside patches of milkweed (Asclepias speciosa), larval host plant for the imperiled monarch butterfly (Danaus plexippus), in a survey of over 900 miles of southern Idaho highways. Based on these results and a literature review, we recommend management strategies to promote the health of pollinator populations in Idaho’s rights-of-way and provide data to help ITD prioritize areas for pollinator-friendly management practices and habitat restoration within their highway system.Item Characterization Factors to Assess Land Use Impacts on Pollinator Abundance in Life Cycle Assessment(American Chemical Society, 2023-02) Alejandre, Elizabeth M.; Scherer, Laura; Guinée, Jeroen B.; Aizen, Marcelo A.; Albrecht, Matthias; Balzan, Mario V.; Bartomeus, Ignasi; Bevk, Danilo; Burkle, Laura A.; Clough, Yann; Cole, Lorna J.; Delphia, Casey M.; Dicks, Lynn V.; Garratt, Michael P.D.; Kleijn, David; Kovács-Hostyánszki, Anikó; Mandelik, Yael; Paxton, Robert J.; Petanidou, Theodora; Potts, Simon; Sárospataki, Miklós; Schulp, Catharina J.E.; Stavrinides, Menelaos; Stein, Katharina; Stout, Jane C.; Szentgyörgyi, Hajnalka; Varnava, Androulla I.; Woodcock, Ben A.; van Bodegom, Peter M.While wild pollinators play a key role in global food production, their assessment is currently missing from the most commonly used environmental impact assessment method, Life Cycle Assessment (LCA). This is mainly due to constraints in data availability and compatibility with LCA inventories. To target this gap, relative pollinator abundance estimates were obtained with the use of a Delphi assessment, during which 25 experts, covering 16 nationalities and 45 countries of expertise, provided scores for low, typical, and high expected abundance associated with 24 land use categories. Based on these estimates, this study presents a set of globally generic characterization factors (CFs) that allows translating land use into relative impacts to wild pollinator abundance. The associated uncertainty of the CFs is presented along with an illustrative case to demonstrate the applicability in LCA studies. The CFs based on estimates that reached consensus during the Delphi assessment are recommended as readily applicable and allow key differences among land use types to be distinguished. The resulting CFs are proposed as the first step for incorporating pollinator impacts in LCA studies, exemplifying the use of expert elicitation methods as a useful tool to fill data gaps that constrain the characterization of key environmental impacts.Item Wildfire severity alters drivers of interaction beta-diversity in plant–bee networks(Wiley, 2022-01) Burkle, Laura A.; Belote, R. Travis; Myers, Jonathan A.Spatial variation in species interactions (interaction β-diversity) and its ecological drivers are poorly understood, despite their relevance to community assembly, conservation and ecosystem functioning. We investigated effects of wildfire severity on patterns and four proximate ecological drivers of interaction β-diversity in plant–bee communities across three localities in the northern Rocky Mountains (Montana, USA). Wildfires decreased interaction β-diversity but increased interaction frequency (number of visits) and richness (number of links). After controlling for interaction frequency and richness, standardized effect sizes of interaction β-diversity were highest following mixed-severity wildfires, intermediate following high-severity wildfires and lowest in unburned landscapes, suggesting that wildfire increases spatial aggregation of plant–bee interactions. Moreover, higher effect sizes in burned landscapes were largely determined by turnover in the species composition of both trophic levels rather than by interaction rewiring (spatial turnover in local species interactions not due to species turnover). The underrepresented level of rewiring indicated spatial consistency in post-disturbance patterns of interactions among co-occurring species. Together, our findings suggest that wildfire alters the β-diversity of mutualistic species interactions via linked assembly of plant–bee communities and provide insights into how environmental change alters complex networks of species interactions.Item Proximity to wildflower strips did not boost crop pollination on small, diversified farms harboring diverse wild bees(Elsevier, 2022-05) Delphia, Casey M.; O'Neill, Kevin M.; Burkle, Laura A.The yield of many agricultural crops depends on pollination services provided by wild and managed bees, many of which are experiencing declines due to factors such as reductions in floral resources. Thus, improving pollinator habitat on farmlands using management strategies like planting wildflower strips is vital for wild bee conservation and sustainable crop pollination. Yet, few studies have examined whether and at what spatial scales wildflower strips enhance crop pollination and yields, and most research has been conducted in large-scale commercial agriculture. Therefore, we investigated the effects of wildflower strips on crop pollination on small, diversified farms (i.e., those growing a variety of crop species) where wild bee diversity and abundance is predicted to be comparatively high. Over three years, on four diversified farms in Montana USA, we tested the hypothesis that distance (20, 60, and 180 m) of crops from native perennial wildflower strips planted alongside crop fields affected wild bee visitation, pollination, and yields of squash and sunflower crop plants. We found that distance to wildflower strips did not affect bee visitation or pollination in crops. Squash yield was pollen-limited in the growing season prior to wildflower strip establishment, and in one of the two years after wildflower strip establishment, but proximity to wildflower strips did not influence the magnitude of pollen limitation. Sunflower seed production was not pollen-limited in any year. Our findings demonstrate that even on diverse farms with wildflower strips and a demonstrated high diversity of bees, some crops do not necessarily receive maximum pollination, regardless of distance from the wildflower strips. However, the value of wildflower strips for supporting wild bee diversity, and other ecological or economic benefits, needs consideration for a full understanding of this pollinator habitat management strategy.Item Asynchrony between solitary bee emergence and flower availability reduces flower visitation rate and may affect offspring size(Elsevier, 2021-08) Slominski, Anthony H.; Burkle, Laura A.Climate change can disrupt plant-pollinator interactions when shifts in the timing of pollinator activity and flowering occur unequally (i.e., phenological asynchrony). Phenological asynchrony between spring-emerging solitary bees and spring-flowering plants may cause bees to experience food deprivation that can affect their reproductive success. However, the mechanisms underlying the effects of food deprivation on solitary bee reproduction remain unknown. We investigated 1) whether food deprivation caused by phenological asynchrony affects solitary bee reproduction by influencing female lifespan and/or visitation to flowers, and 2) the relationship between the magnitude of asynchrony and bee responses. We simulated phenological asynchrony by depriving emerged female Osmia cornifrons (a spring-active solitary bee species) of nectar and pollen for 0 to 16 days. Following asynchrony treatments, we used flight cages to monitor 1) post-treatment female lifespan, 2) flower visitation, and 3) reproduction (i.e., total offspring, offspring weight, sex ratio). We found that post-treatment female lifespan was not affected by phenological asynchrony treatments, but that flower visitation rate and offspring weight decreased as the magnitude of asynchrony increased. Due to low offspring production and a lack of female offspring across treatments, we were unable to assess the effects of phenological asynchrony on total offspring produced or sex ratio. Findings suggest that post-emergence food deprivation caused by phenological asynchrony may affect offspring size by influencing nest-provisioning rates. In solitary bees, body size influences wintering survival, fecundity, and mating success. Thus, phenological asynchrony may have consequences for solitary bee populations that stem from reduced flower visitation rates, and these consequences may increase as the magnitude of asynchrony increases. Because many wild flowering plants and crops rely on pollination services provided by bees for reproductive success, bee responses to phenological asynchrony may also affect wild plant biodiversity and crop yields.Item Earlier spring snowmelt drives arrowleaf balsamroot phenology in montane meadow(Wiley, 2022-08) Durney, J. Simone; Engel, Arden; Debinski, Diane M.; Burkle, Laura A.Climate change is shifting phenology globally, altering when and how species respond to environmental cues such as temperature and the timing of snowmelt. These shifts may result in phenological mismatches among interacting species, creating cascading effects on community and ecosystem dynamics. Using passive warming structures and snow removal, we examined how experimentally increased temperatures, earlier spring snowmelt, and the poorly understood interaction between warming and earlier spring snowmelt affected flower onset, flowering duration, and maximum floral display of the spring-flowering montane species, arrowleaf balsamroot (Balsamorhiza sagittata), over a 7-year period. Additionally, potential cumulative effects of treatments were evaluated over the study duration. The combination of heating with snow removal led to earlier flower onset, extended flowering duration, and increased maximum floral display. While there was year-to-year variation in floral phenology, the effect of heating with snow removal on earlier onset and maximum floral display strengthened over time. This suggests that short-term studies likely underestimate the potential for climate change to influence phenological plant traits. Overall, this research indicates that B. sagittata's flowering onset responded more strongly to snow removal than to heating, but the combination of heating with snow removal allowed plants to bloom earlier, longer, and more profusely, providing more pollinator resources in spring. If warming and early snowmelt cause similar responses in other plant species, these patterns could mitigate phenological mismatches with pollinators by providing a wider window of time for interaction and resiliency in the face of change. This example demonstrates that a detailed understanding of how spring-flowering plants respond to specific aspects of predicted climatic scenarios will improve our understanding of the effects of climate change on native plant–pollinator interactions in montane ecosystems. Studies like this help elucidate the long-term physiological effects of climate-induced stressors on plant phenology in long-lived forbs.Item Effects of Temperature and Wildflower Strips on Survival and Macronutrient Stores of the Alfalfa Leafcutting Bee (Hymenoptera: Megachilidae) Under Extended Cold Storage(Oxford University Press, 2022-08) Park, Mia G.; Delphia, Casey M.; Prince, Cassandra; Yocum, George D.; Rinehart, Joseph P.; O’Neill, Kevin M.; Burkle, Laura A.; Bowsher, Julia H.; Greenlee, Kendra J.Megachile rotundata (F.) is an important pollinator of alfalfa in the United States. Enhancing landscapes with wildflowers is a primary strategy for conserving pollinators and may improve the sustainability of M. rotundata. Changing cold storage temperatures from a traditionally static thermal regime (STR) to a fluctuating thermal regime (FTR) improves overwintering success and extends M. rotundata’s shelf life and pollination window. Whether floral resources enhance overwintering survival and/or interact with a thermal regime are unknown. We tested the combined effects of enhancing alfalfa fields with wildflowers and thermal regime on survival and macronutrient stores under extended cold storage (i.e., beyond one season). Megachile rotundata adults were released in alfalfa plots with and without wildflower strips. Completed nests were harvested in September and stored in STR. After a year, cells were randomly assigned to remain in STR for 6 months or in FTR for a year of extended cold storage; emergence rates were observed monthly. Macronutrient levels of emerged females were assessed. FTR improved M. rotundata survival but there was no measurable effect of wildflower strips on overwintering success or nutrient stores. Timing of nest establishment emerged as a key factor: offspring produced late in the season had lower winter survival and dry body mass. Sugars and glycogen stores increased under FTR but not STR. Trehalose levels were similar across treatments. Total lipid stores depleted faster under FTR. While wildflowers did not improve M. rotundata survival, our findings provide mechanistic insight into benefits and potential costs of FTR for this important pollinator.
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