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.