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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.

 

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.