Habitat loss increases seasonal interaction rewiring in plant-pollinator networks

Understanding the flexibility of interactions and network rewiring (i.e.
reassembly of interactions due to partner-switching) is necessary to
comprehend how future anthropogenic changes will affect interspecific
interactions and the functioning of communities. A higher rewiring could
be expected in more disturbed landscapes because these landscapes contain
fewer and more generalist species with more homogeneous traits. We sampled
pollination interactions in 20 wild Olea europaea communities along a
disturbance gradient to evaluate the hypothesis that the loss of natural
habitats increases seasonal (within-year) interaction rewiring in
plant-pollinator communities, influencing their functional structure. For
this, we particularly tested whether rewiring frequency was negatively
related to the extent of natural habitats surrounding the communities,
whether interaction rewiring influenced the static structure of networks
(nestedness, network specialization –H2’–), and whether a high
generalization (low specialization –d’–) and abundance of species in
communities made them more prone to rewiring. We show that habitat loss
increased seasonal interaction rewiring in networks. Changes in rewiring
were related to changes in the cumulative static structure of pollination
networks. Nestedness decreased and network specialization (H2’) also
tended to decrease as interaction rewiring increased, suggesting an
indirect effect of habitat loss on the robustness of networks through
their dynamics. As expected, generalist insect and plant species were more
prone to rewiring. However, flower abundance had different effects on the
rewiring probability of plant species depending on the extent of habitat
loss, with abundant species rewiring more in disturbed communities and
rewiring less in more natural communities. Likely, this is related to the
context-dependent foraging behaviour of pollinators, which may switch to
more abundant species if the cost of searching for trait-matching
resources is high in disturbed habitats. Our work shows the role of
partner-switching in generalist species to adapt to new conditions. It
also highlights the importance of going beyond general network metrics to
understand the underlying processes of community-level interaction
assembly, and predict and anticipate the effects of anthropogenic
disturbances on pollination services.