Introduction
Species interaction networks may be regarded as blueprints of the architecture of biodiversity, depicting complex webs of interactions among species (Bascompte & Jordano 2007). These networks are typically represented and analysed as observations aggregated over time and space; but, explicitly examining the temporal and spatial dimensions of these networks can increase our understanding of the ecological and evolutionary processes that shape their structure and their robustness to human-caused environmental change (Trøjelsgaard & Olesen 2016; CaraDonna et al. in press).
In recent years there has been increased interest in the temporal and spatial aspects of species interaction networks (Bascompte & Jordano 2014; Trøjelsgaard & Olesen 2016; Schwarz et al. 2020; CaraDonna et al. in press). A consistent pattern emerging from such studies is that most interactions are highly dynamic while few are persistently observed over time and space. For example, Aizen et al. (2012) observed few plant–pollinator interactions consistently throughout a series of isolated hilltops, while Chacoff et al. (2018) observed few interactions consistently across six years. In both studies, the interactions that occurred consistently across time or space tended to involve generalist species, those that interact with many other species, at the network core, the most densely connected part of the network. Understanding how interactions persist across time and space at multiple scales is important for predicting their vulnerability to anthropogenic stressors and for prioritizing the conservation of species that contribute to community robustness (Simmons et al. 2019).
Conceivably species’ tolerances to environmental conditions across time and space may affect generalization and thus network position. For example, pollinator species that tolerate a broad range of environmental conditions across time and space could interact with more plant species, as they are more likely to encounter more species compared to pollinators with narrower tolerances and restricted spatiotemporal activity. Similarly, plant species that flower under a broad range of environmental conditions could interact with more pollinator species due to greater spatiotemporal overlap with pollinator partner species.
We collected data on plant–pollinator interactions throughout the flowering season for five years across six plots in a subalpine meadow in the Colorado Rocky Mountains with the goal of identifying the attributes of interactions that determine their persistence across time and space. We hypothesized that species tolerance to environmental conditions over time and space may determine interaction persistence by constraining temporal and spatial overlap with partner species. Thus, we predicted that interactions with higher temporal and spatial persistence (i.e., those with longer phenophases, higher inter-annual persistence, and broader spatial occurrence) would occur at the network core.