COS 132-1 - Complex patterns of temporal mismatch driven by intra- and inter-specific variation in phenological sensitivity

Abstract: Dramatic shifts in timing of life history events can significantly influence the ecological synchrony among interacted species. Plant-pollinator mutualisms highly rely upon the synchrony, while climate change can substantially disrupt it as phenological responses to climate vary within and across species. However, intra- and interspecific variation in phenological responses is seldom considered simultaneously, limiting our understanding of climate change impacts on interactions among taxa across their ranges. Here, we focused on a unique system, comprising a wide-ranged understory spring ephemeral with varying color morphs (Claytonia virginica) and its specialist bee pollinator (Andrena erigeniae) in the United States. Using natural history collections (e.g., digitized herbarium specimens) and citizen science observations from iNaturalist, we investigated how variation in phenological sensitivity to climate alter ecological interactions simultaneously within and among species. Phenological sensitivity to warming was quantified using linear mixed-effect models within and between flowering time of C. virginica and occurrence of A. erigeniae across ecoregions within their ranges. We found opposing trends in the phenological sensitivities of plants versus their pollinators across their geographic ranges. Flowering phenology was more sensitive to temperature in warmer regions up to ‒2.8 days/°C, whereas bee phenology was more responsive to temperature in colder regions up to ‒3.3 days/°C. Phenological sensitivity also varied across flower color morphs between pink and white flowers. Increased temporal separation up to 6 days between flowering times and pollinator activity were predicted across the species’ ranges in the future by 2081-2100. Further, we found that the phenology of co-occurring canopy trees also varies across the species’ ranges, adding another dimension of complexity to these multi-species temporal interactions using forest phenology derived from satellite imagery. Specifically, canopy greenup date was more sensitive to warming in winter and spring than flowering of C. virginica in the northern part of its range. However, C. virginica flowering time was more sensitive to warming than the canopy greenup in most of the southern part of its range. Continuous warming in the future was predicted to decrease the time between spring beauty flowering and canopy greenup in northern regions, suggesting shortened shade-free time for C. virginica. Our work demonstrates the complexity and fragility of ecological interactions in time and the necessity of incorporating variation in phenological responses across multiple axes to understand how such interactions will change in the future driven by the global change.