Conclusions
Concerns about the ecological consequences of changes in bee
biodiversity are leading to increased recognition of the importance of
wild bee conservation and promoting wild bees in agricultural systems
(Isaacs and Kirk, 2010, Biddinger et al., 2018, Reilly et al. 2020). But
wild bee communities are diverse and dynamic, and little is known about
what species or groups have the greatest conservation needs. Our
intensive sampling across six years shows that bee communities vary
greatly from month to month for all measures of biodiversity. For
monitoring efforts to capture the full breadth of bee biodiversity, it
is important to sample bees across all seasons, especially during spring
when communities turnover rapidly. Biodiversity changes across the six
years of our study were less dramatic than seasonal changes, but we
found evidence of biodiversity loss over time with declines in abundance
in 33% of the species. Notably, our results indicate that bee family is
not a good predictor of changes over time, and in some cases, closely
related species showed very different patterns. This suggests that
species-specific traits may be more important predictors of long-term
population dynamics than shared evolutionary history. We recommend that
future monitoring efforts that seek to understand species-level dynamics
for multiple co-occurring species, and whole-community patterns in
biodiversity, utilize standardized collection methods repeated over
multiple years. Longer-term and species-specific data on wild bee
dynamics could provide greater insight into which species need targeted
conservation efforts (Woodard et al., 2020).
Acknowledgments
We thank the orchard fruit grower Scott Slaybaugh, Jim Lerew, Bill
Pulig, and Barry Rice for allowing us to conduct studies on their land
and to Jim Gillis and Mace Vaughan for their support in establishing the
USDA-NRCS wildflower strips. Thank you to Kathryn Wholaver, Lolita
Miller, Sarah Heller, and many others at the Pennsylvania State Fruit
Research and Extension Center. Jason Gibbs, Robert Jean, and Sam Droege
identified bees and the members of the López-Uribe Lab provided helpful
feedback on the previous versions of the manuscript. This research was
supported by a Pennsylvania Department of Agriculture Grant number
C940000555, and USDA-NIFA-AFRI Specialty Crop Research Initiative,
Project 2012-51181-20105. DJB was funded through the USDA NIFA
Appropriations under Project PEN04620. MML-U was funded through the USDA
NIFA Appropriations under Projects PEN04716 and PEN04620.
Conflicts of interest
The authors declare no conflicts of interest.
Data availability
statement
The data used in this study will be posted on Dryad after the paper is
accepted for publication.
Author contributions
Nash E. Turley: Formal analysis (lead); Visualization (lead); Writing –
original draft (lead); Writing – review & editing (equal)
David J. Biddinger: Conceptualization (equal); Funding acquisition
(equal); Investigation (lead); Methodology (equal); Writing – review &
editing (equal)
Neelendra K. Joshi: Conceptualization (equal); Investigation (equal);
Methodology (equal); Writing – review & editing (equal)
Margarita M. López-Uribe: Conceptualization (equal), Funding acquisition
(lead); Writing – review & editing (lead)