Climate change may disrupt interspecies phenological synchrony, with adverse consequences to ecosystem functioning. We present here a 40-y-long time series on 10,425 dates that were systematically collected in a single Russian locality for 97 plant, 78 bird, 10 herptile, 19 insect, and 9 fungal phenological events, as well as for 77 climatic events related to temperature, precipitation, snow, ice, and frost. We show that species are shifting their phenologies at dissimilar rates, partly because they respond to different climatic factors, which in turn are shifting at dissimilar rates. Plants have advanced their spring phenology even faster than average temperature has increased, whereas migratory birds have shown more divergent responses and shifted, on average, less than plants. Phenological events of birds and insects were mainly triggered by climate cues (variation in temperature and snow and ice cover) occurring over the course of short periods, whereas many plants, herptiles, and fungi were affected by long-term climatic averages. Year-to-year variation in plants, herptiles, and insects showed a high degree of synchrony, whereas the phenological timing of fungi did not correlate with any other taxonomic group. In many cases, species that are synchronous in their year-to-year dynamics have also shifted in congruence, suggesting that climate change may have disrupted phenological synchrony less than has been previously assumed. Our results illustrate how a multidimensional change in the physical environment has translated into a community-level change in phenology.global warming | mismatch | trophic interactions | boreal forest T he timing of phenological events is shifting as a result of climate change (1-5). Together with other adaptive mechanisms, plasticity in phenology is essential for maintaining many aspects of biodiversity in a changing environment (5-7), such as species' demography (8), species interactions (3), and species distributions (9). As different species within a community may show different responses to climate variation (10, 11), many studies have speculated on the possibility that phenological synchrony within ecological communities may be extensively disrupted (12-15). Conversely, other studies including observational evidences, theoretical considerations, and small-scale experiments have suggested that the maintenance of synchrony in terrestrial and aquatic systems may be common (16)(17)(18)(19). Therefore, the extent to which the stability and persistence of natural systems will be hampered as a result of loss of phenological synchrony remains largely an open question. Addressing this pertinent question is challenging because of the complex, dynamic, and often poorly understood structure of ecological interaction networks.To date, most studies evaluating the maintenance or disruption of phenological synchrony have examined whether longterm phenological shifts have been congruent between interacting species and environmental conditions (18,20). The majority of these studies have describ...

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For species to stay temporally tuned to their environment, they use cues such as the accumulation of degree-days. The relationships between the timing of a phenological event in a population and its environmental cue can be described by a population-level reaction norm. Variation in reaction norms along environmental gradients may either intensify the environmental effects on timing (cogradient variation) or attenuate the effects (countergradient variation). To resolve spatial and seasonal variation in species’ response, we use a unique dataset of 91 taxa and 178 phenological events observed across a network of 472 monitoring sites, spread across the nations of the former Soviet Union. We show that compared to local rates of advancement of phenological events with the advancement of temperature-related cues (i.e., variation within site over years), spatial variation in reaction norms tend to accentuate responses in spring (cogradient variation) and attenuate them in autumn (countergradient variation). As a result, among-population variation in the timing of events is greater in spring and less in autumn than if all populations followed the same reaction norm regardless of location. Despite such signs of local adaptation, overall phenotypic plasticity was not sufficient for phenological events to keep exact pace with their cues—the earlier the year, the more did the timing of the phenological event lag behind the timing of the cue. Overall, these patterns suggest that differences in the spatial versus temporal reaction norms will affect species’ response to climate change in opposite ways in spring and autumn.

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