Abstract:
Across an elevation gradient, several biotic and abiotic factors influence community
assemblages of interacting species leading to a shift in species distribution, functioning,
and ultimately topologies of species interaction networks. However, empirical
studies of climate-driven
seasonal and elevational changes in plant-pollinator
networks
are rare, particularly in tropical ecosystems. Eastern Afromontane Biodiversity
Hotspots in Kenya, East Africa. We recorded plant-bee
interactions at 50 study sites
between 515 and 2600 m asl for a full year, following all four major seasons in this region.
We analysed elevational and seasonal network patterns using generalised additive
models (GAMs) and quantified the influence of climate, floral resource availability,
and bee diversity on network structures using a multimodel inference framework. We
recorded 16,741 interactions among 186 bee and 314 plant species of which a majority
involved interactions with honeybees. We found that nestedness and bee species
specialisation of plant-bee
interaction networks increased with elevation and that the
relationships were consistent in the cold-dry
and warm-wet
seasons respectively. Link
rewiring increased in the warm-wet
season with elevation but remained indifferent in
the cold-dry
seasons. Conversely, network modularity and plant species were more
specialised at lower elevations during both the cold-dry
and warm-wet
seasons, with
higher values observed during the warm-wet
seasons. We found flower and bee species
diversity and abundance rather than direct effects of climate variables to best
predict modularity, specialisation, and link rewiring in plant-bee-
interaction
networks.
This study highlights changes in network architectures with elevation suggesting a potential
sensitivity of plant-bee
interactions with climate warming and changes in rainfall
patterns along the elevation gradients of the Eastern Afromontane Biodiversity
Hotspot.
