Data from: Beta diversity and specialization in plant-pollinator networks along an elevational gradient

Aim: To assess whether the reduced nutritional resources available for
pollinators due to plant community simplification along an elevational
plant-diversity gradient changes pollinator niche breadth and richness.
Additionally, we evaluated how body size and proboscis length of
pollinators shifted along the gradient, and whether these changes were
related to pollinator niche breadth. Location: An elevational gradient
(2,350-3,520 m a.s.l.) on the oceanic high-mountain strato-volcano of El
Teide (Tenerife, Canary Islands). Taxon: Flowering plant and pollinator
species. Methods: We compared quantitative plant–pollinator networks along
the plant-diversity gradient. We calculated a set of niche-based
topological metrics that capture the degree of specialization, niche
breadth and niche overlap. Furthermore, we obtained β-diversity measures
and the proportion of replacement and richness components. Results: There
was an overall decline in species richness of pollinators with increasing
elevation. This decline was mainly driven by the loss of species along the
elevational gradient, which conformed a nested subset pattern. The whole
network showed less specialization, greater connectance and lower
modularity towards the summit. At high elevations, pollinators were more
generalized and less selective in their flower choice, showing a greater
trophic niche breadth compared to pollinators at lower elevations. Mean
body size of pollinators increased with elevation, and species body size
and proboscis length were positively associated with the number of plant
species visited. Main conclusions. Overall, results indicated that the
elevational gradient filters pollinator species, probably according to
their thermal tolerance and ability to exploit a wide range of trophic
resources. The finding that pollinators become more generalized and
opportunistic at higher elevations is a novel result, which may have
implications for new research into how ecological networks vary over
environmental gradients. From an applied perspective, our results
highlight the importance of considering the spatial variation of species
assemblages when aiming to construct functionally reliable interaction
networks along environmental gradients.