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Abstract Plant-pollinator interaction networks are dynamic in time and space. Interaction turnover consists of interaction rewiring (i.e., changes in interactions independent of species turnover) and species turnover (i.e., the gain or loss of species present in the network). To capture network dynamics, it is crucial to address the effect of sampling effort because insufficient data can distort apparent network patterns. We used eight years of plant-pollinator interaction data from a subalpine meadow to examine patterns of temporal (week-to-week) interaction turnover and the role of sampling effort. With increasing sampling effort, values of interaction turnover and species turnover decreased, and rewiring increased. Saturation curves suggest an approach towards true values with higher sampling effort. Across the eight years, substantial variation in weekly and seasonal interaction turnover was observed, with identifiable seasonal trends across all aggregated years. These results demonstrated that the interpretation of interaction turnover and its components is sensitive to sampling effort, stressing the importance of considering its role in network studies. 

Abstract Understanding the ranges of rare and endangered species is central to conserving biodiversity in the Anthropocene. Species distribution models (SDMs) have become a common and powerful tool for analyzing species–environment relationships across geographic space. Although evaluating the distribution of rare species is integral to their conservation, this can be difficult when limited distribution data are available. Community science platforms, such as iNaturalist, have emerged as alternative sources for species occurrence data. Although these observations are often thought to be of lower quality than those of natural history collections, they may have potential for improving SDMs for species with few occurrence records from collections. Here, we investigate the utility of iNaturalist data for developing SDMs for a rare high‐elevation plant,Telesonix jamesii. Because methods for modeling rare species are limited in the literature, five different modeling techniques were considered, including profile methods, statistical models, and machine learning algorithms. The inclusion of iNaturalist data doubled the number of usable records forT. jamesii.We found that a random forest (RF) model using ensemble training data performed the highest of any model (area under curve = 0.98). We then compared the performance of RF models that use only natural history training data and those that use a combination of natural history (herbarium specimens) and iNaturalist training data. All models heavily relied on climate data (mean temperature of driest quarter, and precipitation of the warmest quarter), indicating that this species is under threat as climate continues to change. Validation datasets affected model fits as well. Models using only herbarium data performed slightly poorer when evaluated with cross‐validation than when validated externally with iNaturalist data. This study can serve as a model for future SDM studies of species with similar data limitations. 

Mutualistic interactions between plants and pollinators play an important role in supporting biodiversity and ecosystem stability. However, these interactions are increasingly threatened by climate change, which can alter the phenology of species and cause temporal mismatches between interacting partners. Leveraging historical and contemporary datasets collected more than a century apart, we investigated phenological shifts in plants and pollinators and the impact of changes in temporal overlap of the interaction partners on the persistence of their interactions. We found that generally, the onset of flowering and insect activity started earlier and has lasted longer in the present. We also found that greater temporal overlap of plant and pollinator species predicted a higher probability of persistence of their interaction between time periods. Our results document phenological shifts over a century, and emphasize the importance of maintaining phenological matching for the persistence of plant-pollinator interactions. This illustrates the value of historical data sets for understanding long-term ecological dynamics in the face of accelerating environmental change. 

Climate change‐induced range shifts can disrupt interactions among species by moving them in and out of ecological communities. These disruptions can include impacts on competition for shared resources. Bumble bees (Bombusspp.) are important pollinators shifting their range upwards in elevation in response to climate change. These shifts could lead to altered competition among species and threaten co‐existence. This could be particularly worrying at the tops of mountain ranges where bumble bees may no longer be able to move up to higher elevations to track climate change. To better understand this issue, we investigated changes in diet niche overlap among bumble bee species along a 2296 m elevation gradient in the southern Rocky Mountains. Additionally, we investigated how morphological and phenological traits impact diet composition (flower species visited) among bumble bee species and explored a simple simulation to understand how the continued upward movement of bumble bee species under climate change into the mountaintop may affect trait overlap of newly co‐occurring species. We found that diet niche overlap among bumble bee species increased with elevation. We also found that differences in morphological and phenological traits (body size, tongue length, date of activity) were correlated with differences in diet composition among bumble bee species. Finally, we described how the co‐occurrence of bumble bee species from lower elevations with mountaintop species would lead to increased trait overlap and likely more species sharing similar flowers. These shifts could lead to increased competition for high‐elevation restricted species on mountaintops and exacerbate the effects of climate change on high‐elevation bumble bees. 

Telesonix jamesii, a rare and imperiled species of perennial saxifrage, is restricted to rocky habitats at high elevations across 21 isolated, known populations in the southern Rocky Mountains of Colorado and New Mexico. Despite its imperiled conservation status, very little is known about the natural history of T. jamesii. We studied pollination of this species during the summers of 2019–2021 at multiple locations on Pikes Peak, Colorado. We conducted a total of 899 min of pollinator surveys, identifying all floral visitors during this time period. We then examined floral visitors for the presence of T. jamesii pollen to determine which species might be effective pollinators. We found that flowers of T. jamesii are visited by a diverse assemblage of insects and one species of hummingbird. Bumble bees (Bombus) were the most commonly observed species visiting flowers, as well as the only group found carrying T. jamesii pollen on their bodies. Our findings suggest that T. jamesii is infrequently pollinated, and we speculate that gene flow for this species may be low. This work constitutes the first investigation into the field pollination ecology of T. jamesii. Our study warrants future investigation into the population genetics of this species as well as surveys of historical occurrences and high-suitability habitat for populations.