Data from: Landscape and local factors influence solitary bee nesting, but reported effects show little consistency across studies

Solitary bees constitute 75% of bee species but are understudied compared
with social bees. Because of global pollinator declines, it is critical to
develop effective conservation measures for solitary bees. Consequently, a
thorough understanding of the local and landscape factors that influence
nesting of above-ground nesting (AGN) and below-ground nesting (BGN)
species is required. We performed a systematic review of the scientific
literature with respect to solitary bee nesting behaviour. A screening of
~15,000 articles resulted in 91 articles providing meaningful data for AGN
bees and 55 articles for BGN bees. For AGN bees, we extracted information
on factors such as nest orientation, nest height, cavity size, and nest
materials. For BGN bees, we extracted information on factors such as
ground aspect and slope, bare soil, and vegetation height. The effects of
floral resources, prevalence of semi-natural habitat, and wider habitat
type, were recorded for both AGN and BGN bees. Considering the factors
examined in the existing literature, both AGN and BGN bees displayed
higher nest occupancy in sites associated with semi-natural habitat and/or
high floral abundance. For AGN bees, trap nest occupancy was associated
with nest site characteristics such as the construction material and
cavity diameter, while for BGN bees nesting was associated with the
prevalence of bare ground. Notably, however, the reported effects of most
explanatory factors on solitary bee nesting behaviour were highly
inconsistent across studies. Synthesis and applications: Collectively,
these findings indicate that agri-environment schemes aiming to support
solitary bees should integrate the provision of nesting resources with
proximity to floral resources. The heterogeneity among studies highlights
the need for solitary bee conservation measures to be tailored to local
conditions and to the local fauna. Where possible, nest site
interventions, such as the placement of trap nests and substrate
properties, should be tested experimentally across biogeographic zones to
clarify their effects and assess the consistency of responses under
different environmental conditions.