Successional and phenological effects on plant-floral visitor interaction networks of a tropical dry forest

1. Plant-pollinator interactions are fundamental to ecosystem functioning;
however, the role that succession and phenology have on these interactions
is poorly understood, particularly in endangered tropical ecosystems. In
highly diverse ecosystems such as tropical dry forests (TDF), variation in
water and food availability determines the life cycles of animal
pollinators. Therefore, understanding patterns of flowering phenology and
plant-pollinator interactions across seasons in successional environments
is key to maintaining and restoring TDF. 2. We analysed the functional
dynamics of plant-floral visitor interactions at the community level
across a successional gradient in a Mexican TDF. We evaluated changes in
the diversity of blooming plant species and floral visitors, phenological
patterns, interaction network metrics, and beta diversity among early,
intermediate, and late successional stages, between dry and rainy seasons.
3. We found a higher diversity of blooming plant species and a higher
richness of animal species in the intermediate and late successional
stages. Peak abundance of floral visitors overlapped with flowering peaks
in the late successional stages, but this was not consistently the case in
the early and intermediate stages. Plant-floral visitors networks differed
in structure according to successional stage and season, but
specialisation metrics were higher in late successional stages.
Interaction networks were more dissimilar between dry and rainy seasons
within successional stages than within seasons between successional
stages, suggesting connectivity across successional sites during each
season. In addition, closely related plant species do not share the same
pollination systems in any successional stage. 4. Synthesis. Our results
showed that plant-floral visitor interactions are dynamic and vary with
flowering phenology and with successional changes in plant and animal
diversity. Plant-floral visitor interactions were more diverse and
specialised in the late successional stages. In the rainy season,
differences in network structure among successional stages are due to
interaction rewiring, while in the dry season, it is caused by species
turnover. Our results demonstrate that seasonality plays a key role in
community diversity and network structure and highlight the importance of
conserving mature forests to ensure the maintenance of critical
pollination interactions across all successional stages.