Differential impacts of land use change on multiple components of common Milkweed (Asclepias syriaca) pollination success

Land-use change is one the greatest threats to biodiversity and is
projected to increase in magnitude in the coming years, stressing the
importance of better understanding how land-use change may affect vital
ecosystem services, such as pollination. Past studies on the impact of
land-use change have largely focused on only one aspect of the pollination
process (e.g. pollinator composition, pollinator visitation, pollen
transfer), potentially misrepresenting the full complexity of land-use
effects on pollination services. Evaluating the impacts across multiple
components of the pollination process can also help pinpoint the
underlying mechanisms driving land-use change effects. This study
evaluates how land-use change affects multiple aspects of the pollination
process in common milkweed populations, including pollinator community
composition, pollinator visitation rate, pollen removal, and pollen
deposition. Overall, land-use change altered floral visitor composition,
with small bees having a larger presence in developed areas. Insect
visitation rate and pollen removal were also higher in more developed
areas, perhaps suggesting a positive impact of land-use change. However,
pollen deposition did not differ between developed and undeveloped sites.
Our findings highlight the complexity evaluating land-use change effects
on pollination, as these likely depend on the specific aspect of
pollination evaluated and on the of the intensity of disturbance. Our
study stresses the importance of evaluating multiple components of the
pollination process in order to fully understand overall effects and
mechanisms underlying land-use change effects on this vital ecosystem
service.