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Phenology, the timing of recurrent biological events, is a key mechanism by which species adapt or acclimatize to variable environmental conditions, including those influenced by climate change. Measurable traits, including the onset and end of activity, peak activity, and duration, characterize the phenology of life events, and could be significant predictors of trends in population abundance or stability in a changing climate. Bees provide critical pollination services, and understanding the covariates of bee phenological traits can refine predictions on the vulnerabilities of bees and their services to climate change. We paired 16 years of monthly bee survey data (2002-2019) with climate data for 74 bee species in dryland ecosystems of central New Mexico, USA. Contrary to the current paradigm of temperature as the key driver of insect phenology, twice as many bee species had phenological sensitivity to precipitation (39%) than to temperature (20%). Among phenological traits, the end date of active flying periods was most sensitive to climate. Of the 20% of bee species for which precipitation predicted activity end date, 73% ended activity later in wetter years. Fifteen bee species (~20%) had phenological traits sensitive to temperature, but temperature sensitivity was idiosyncratic, and only four species had earlier onset in warmer years, as expected from results in other biomes. Oligolectic (diet specialist) bee species began, peaked, and ended activity later in the year than polylectic (generalist) species, but phenological traits did not correlate with sociality. All phenological traits showed phylogenetic signal, suggesting evolutionary conservatism of phenology among the common bees of central New Mexico drylands. Finally, species with long activity durations were more common, had greater temporal stability in abundance from year to year, and were less likely to decline over time, perhaps because of their longer window for resource acquisition. Our results suggest that drier climates of the future may shift bee phenological activities toward earlier onset, peak, and end dates, that bees with short activity durations may be among the most sensitive to declines in future climates, and that both generalist and social bees may be able to resist or recover from climate change if they have long durations of flight activity.
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This content will become publicly available on March 1, 2026
Bumble bee niche overlap along an elevation gradient: how traits can inform novel competitive pressures under climate 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.
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- Award ID(s):
- 2102974
- PAR ID:
- 10630278
- Publisher / Repository:
- Oikos
- Date Published:
- Journal Name:
- Oikos
- Volume:
- 2025
- Issue:
- 3
- ISSN:
- 0030-1299
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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