Tree cover strongly predicts United States Megachiladae biodiversity

Authors: McCabe, Lindsie; CHESSIRE, PAIGE - Northern Arizona University; COBB, NEIL - Northern Arizona University

Submitted to: Diversity and Distributions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2023
Publication Date: 10/26/2023
Citation: Mccabe, L.M., Chessire, P.R., Cobb, N.S. 2023. Tree cover strongly predicts United States Megachiladae biodiversity. Diversity and Distributions. https://doi.org/10.7717/peerj.16145.
DOI: https://doi.org/10.7717/peerj.16145

Interpretive Summary: Megachilidae is one of the most diverse bee families in North America, with about 600 described species in 19 genera. Unlike other bee families, that are primarily ground nesters, many Megachilidae require woody plant material for nesting. Thus, the availability of woody-plant species may be as important as nectar/pollen hosts in constraining biogeographic patterns of Megachilidae diversity. Here we examine Megachilidae biodiversity across the United States and the relationship to climate, nesting substrate and floral resources. We examined the relationship between megachilid species richness and precipitation, temperature, tree cover, tree species richness, and flowering plant diversity. We found three main results: 1) Precipitation predicted Megachilidae richness more than temperature. 2) Forested land cover, but not tree diversity predicted greater Megachilidae richness, which supports the importance of nesting substrate 3) Megachilidae richness was also strongly positively correlated with flowering plant diversity. Trees are particularly susceptible to climate change impacts from drought, fire, and infestations, which may make nesting substrates the limiting resource for how these species respond to climate change.

Technical Abstract: Megachilidae is one of the most diverse bee families in North America, with about 600 described species in 19 genera. Unlike other bee families, that are primarily ground nesters, many Megachilidae require woody plant material for nesting. Thus, the availability of woody-plant species may be as important as nectar/pollen hosts in constraining biogeographic patterns of Megachilidae diversity. Here we examine Megachilidae biodiversity across the United States and the relationship to climate, nesting substrate and floral resources. The distribution of Megachilidae biodiversity was the greatest in the southwestern United States. At three scales (continental, western US, and eastern US) we examined the relationship between megachilid species richness and precipitation, temperature, tree cover, tree species richness, and flowering plant diversity. We found three main results that were consistent at both the continental and regional scales: 1) Precipitation predicted Megachilidae richness more than temperature. 2) Forested land cover, but not tree diversity predicted greater Megachilidae richness, which supports the importance of nesting substrate 3) Megachilidae richness was also strongly positively correlated with flowering plant diversity. Trees are particularly susceptible to climate change impacts from drought, fire, and infestations, which may make nesting substrates the limiting resource for how these species respond to climate change.