Specialization and phenological synchrony of plant–pollinator interactions along an altitudinal gradient

Abstract

Summary 1.One of the most noticeable effects of anthropogenic climate change is the shift in timing of seasonal events towards earlier occurrence. The high degree of variation in species' phenological shifts has raised concerns about the temporal decoupling of interspecific interactions, but the extent and implications of this effect are largely unknown. In the case of plant-pollinator systems, more specialized species are predicted to be particularly threatened by phenological decoupling, since they are assumed to be less flexible in the choice of interaction partners, but until now this hypothesis has not been tested. 2. In this paper, we studied phenology and interactions of plant and pollinator communities along an altitudinal gradient in the Alps as a model for the possible effects of climate change in time. 3. Our results show that even relatively specialized pollinators were much more flexible in their use of plant species as floral resources than their local flower visitation suggested. We found no relationship between local specialization of pollinators and the consistency of their visitation patterns across sites, and also no relationship between specialization and phenological synchrony of pollinators with particular plants. 4. Thus, in contrast to the conclusions of a recent simulation study, our results suggest that most pollinator species included in this study are not threatened by phenological decoupling from specific flowering plants. However, the flexibility of many rarely observed pollinator species remains unknown. Moreover, our results suggest that specialized flower visitors select plant species based on certain floral traits such as the length of the nectar holder tube. If that is the case, the observed flexibility of plant-pollinator interactions likely depends on a high degree of functional redundancy in the plant community, which may not exist in less diverse systems.

Studying plant–pollinator interactions in a changing climate: A review of approaches

“…Because the dynamics of plant–pollinator interactions is a community-level process, studies are needed that assess community changes such as temporal dynamics of coflowering and pollinator communities (e.g., Benadi et al, 2014; Kudo, 2014 [see ]).…”

Changes in host–parasitoid food web structure with elevation

“…In addition, the frequency of interactions may vary with elevation (Péré, Jactel & Kenis ), as well as the temporal overlap in the activity of interacting species (Benadi et al . ). Such asymmetric responses suggest that the structure of food webs may change with elevation.…”

Elevation predicts the functional composition of alpine plant communities based on vegetative traits, but not based on floral traits

“…Less well studied are floral traits that are important for the plants' sexual reproduction, which requires animal pollen vectors in zoophilous plants and was suggested to be of particular importance for alpine plant species (Fabbro and Körner 2004). The few studies that considered floral traits in a community-ecological context (e.g., Benadi et al 2014;Junker et al 2013;Runquist et al 2016;Wolowski et al 2017) suggest a contribution of these traits to plant community composition (Benadi 2015;Pauw 2013;Sargent and Ackerly 2007). Indeed, recent studies show that floral traits, such as morphology, colour, and scent shape plant-pollinator interactions, affect the diversity of flower visiting animals in communities, and explain the presence or absence of competition between plant species for pollinators (Carvalheiro et al 2014;Junker et al 2013Junker et al , 2015Junker and Parachnowitsch 2015;Kuppler et al 2016;Larue et al 2016).…”