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Environmental filtering of body size and darker coloration in pollinator communities indicate thermal restrictions on bees, but not flies, at high elevations.
PeerJ 2019; 7:e7867P

Abstract

Background

Bees and flies are the two most dominant pollinator taxa in mountain environments of the Southwest USA. Communities of both taxa change dramatically along elevation gradients. We examined whether bee and fly traits would also change along elevation gradients and if so, do they change in a predictable way related to a decrease in temperature as elevation increases.

Methods

We used insect body size and darkness traits as proxies for energetic requirements and indicators of cold tolerance in order to assess patterns of bee and fly community trait differences along an elevation gradient. We examined 1,922 individuals of bees and flies sampled along an elevation gradient ranging from 2,400 meters to 3,200 meters and from 9.6 °C to 5.2 °C mean annual temperature. We examined bees and flies separately using community weighted means (site-level trait values weighted by species abundance) and estimates of environmental filtering (quantified as the inverse of the standardized range of trait values).

Results

Bees and flies exhibited two somewhat distinct patterns; (1) Community weighted mean body volume and darkness of bees increased sharply at the highest elevation, and the intensity of environmental filtering also increased with elevation. This was due to both a change among bee populations within a species as well as species replacement at the highest elevation. (2) Community weighted mean body volume and darkness of flies also increased moderately with increasing elevation, but did not exhibit patterns of significant environmental filtering. In fact, the intensity of environmental filtering as indicated by the range of fly body volume weakened with elevation.

Conclusion

The increase in filter intensity at high elevations exhibited by bees suggests a significant limitation on the breadth of viable functional strategies for coping with extreme cold, at least within this regional species pool. Flies, on the other hand, do not appear to be limited by high elevations, indicating that the shift from bee to fly dominance at high elevations may be due, at least in part, to greater environmental constraints on bee adaptation to colder environments.

Authors+Show Affiliations

Merriam-Powell Center for Environmental Research and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, United States of America.Merriam-Powell Center for Environmental Research and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, United States of America.Merriam-Powell Center for Environmental Research and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, United States of America.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31632853

Citation

McCabe, Lindsie M., et al. "Environmental Filtering of Body Size and Darker Coloration in Pollinator Communities Indicate Thermal Restrictions On Bees, but Not Flies, at High Elevations." PeerJ, vol. 7, 2019, pp. e7867.
McCabe LM, Cobb NS, Butterfield BJ. Environmental filtering of body size and darker coloration in pollinator communities indicate thermal restrictions on bees, but not flies, at high elevations. PeerJ. 2019;7:e7867.
McCabe, L. M., Cobb, N. S., & Butterfield, B. J. (2019). Environmental filtering of body size and darker coloration in pollinator communities indicate thermal restrictions on bees, but not flies, at high elevations. PeerJ, 7, pp. e7867. doi:10.7717/peerj.7867.
McCabe LM, Cobb NS, Butterfield BJ. Environmental Filtering of Body Size and Darker Coloration in Pollinator Communities Indicate Thermal Restrictions On Bees, but Not Flies, at High Elevations. PeerJ. 2019;7:e7867. PubMed PMID: 31632853.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Environmental filtering of body size and darker coloration in pollinator communities indicate thermal restrictions on bees, but not flies, at high elevations. AU - McCabe,Lindsie M, AU - Cobb,Neil S, AU - Butterfield,Bradley J, Y1 - 2019/10/14/ PY - 2019/01/08/received PY - 2019/09/10/accepted PY - 2019/10/22/entrez PY - 2019/10/22/pubmed PY - 2019/10/22/medline KW - Bees KW - Body darkness KW - Body size KW - Elevational gradients KW - Flies KW - Functional traits KW - Pollinators SP - e7867 EP - e7867 JF - PeerJ JO - PeerJ VL - 7 N2 - Background: Bees and flies are the two most dominant pollinator taxa in mountain environments of the Southwest USA. Communities of both taxa change dramatically along elevation gradients. We examined whether bee and fly traits would also change along elevation gradients and if so, do they change in a predictable way related to a decrease in temperature as elevation increases. Methods: We used insect body size and darkness traits as proxies for energetic requirements and indicators of cold tolerance in order to assess patterns of bee and fly community trait differences along an elevation gradient. We examined 1,922 individuals of bees and flies sampled along an elevation gradient ranging from 2,400 meters to 3,200 meters and from 9.6 °C to 5.2 °C mean annual temperature. We examined bees and flies separately using community weighted means (site-level trait values weighted by species abundance) and estimates of environmental filtering (quantified as the inverse of the standardized range of trait values). Results: Bees and flies exhibited two somewhat distinct patterns; (1) Community weighted mean body volume and darkness of bees increased sharply at the highest elevation, and the intensity of environmental filtering also increased with elevation. This was due to both a change among bee populations within a species as well as species replacement at the highest elevation. (2) Community weighted mean body volume and darkness of flies also increased moderately with increasing elevation, but did not exhibit patterns of significant environmental filtering. In fact, the intensity of environmental filtering as indicated by the range of fly body volume weakened with elevation. Conclusion: The increase in filter intensity at high elevations exhibited by bees suggests a significant limitation on the breadth of viable functional strategies for coping with extreme cold, at least within this regional species pool. Flies, on the other hand, do not appear to be limited by high elevations, indicating that the shift from bee to fly dominance at high elevations may be due, at least in part, to greater environmental constraints on bee adaptation to colder environments. SN - 2167-8359 UR - https://www.unboundmedicine.com/medline/citation/31632853/Environmental_filtering_of_body_size_and_darker_coloration_in_pollinator_communities_indicate_thermal_restrictions_on_bees,_but_not_flies,_at_high_elevations L2 - https://doi.org/10.7717/peerj.7867 DB - PRIME DP - Unbound Medicine ER -