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Shifts in the timing of flowering are a conspicuous biological signal of climate change. These shifts have been documented across the globe for diverse communities. Although many species are flowering earlier, others have exhibited no shifts or delays in flowering., How species respond phenologically will shape interactions both with other community members and with the abiotic environment, altering fitness, abundance and ultimately persistence., To understand if variability in phenological response is influenced by evolutionary history, we tested for phylogenetic signal in shifts in flowering onset for 13 communities representing 116 families across the Northern Hemisphere. We compared the fit of models of neutral evolution (Brownian Motion) with models that incorporate selection (Ornstein-Uhlenbeck)., We found significant signal in whether species had shifted and the magnitude of response, with both traits conforming to an Ornstein-Uhlenbeck model of trait evolution., Synthesis. These results show there is global phylogenetic signal in the direction and magnitude of shifts in flowering onset and indicate selection has shaped flowering time responses of related species under climate change; thus, environmentally determined optima may constrain whether and to what degree species respond phenologically to climate change. Our findings further demonstrate the value of testing for phylogenetic signal across multiple communities and comparing multiple models of trait evolution. [ABSTRACT FROM AUTHOR]

Climate change may disrupt plant–pollinator mutualisms by generating phenological asynchronies and by altering traits that shape interaction costs and benefits. Our knowledge is limited to studies that manipulate only one partner or focus on either phenological or trait‐based mismatches. We assembled communities of three annual plants and a solitary bee prior to flowering and emergence to test how springtime warming affects phenologies, traits, interactions and reproductive output. Warming advanced community‐level flowering onset, peak and end but did not alter bee emergence. Warmed plant communities produced fewer and smaller flowers with less, more‐concentrated nectar, reducing attractiveness, and warmed bees were more generalized in their foraging, reducing their effectiveness. Plant–bee interactions were less frequent, shorter and peaked earlier under warming. As a result, warmed plants produced fewer, lighter seeds, indicating pollinator‐mediated fitness costs. Climate change will perturb plant–pollinator mutualisms, causing wide‐ranging effects on partner species and diminishing the ecosystem service they provide. [ABSTRACT FROM AUTHOR]

Climate change is known to affect regional weather patterns and phenology; however, we lack understanding of how climate drives phenological change across local spatial gradients. This spatial variation is critical for determining whether subpopulations and metacommunities are changing in unison or diverging in phenology. Divergent responses could reduce synchrony both within species (disrupting gene flow among subpopulations) and among species (disrupting interspecific interactions in communities). We also lack understanding of phenological change in environments where life history events are frequently aseasonal, such as the tropical, arid, and semi-arid ecosystems that cover vast areas. Using a 33-year-long dataset spanning a 1,267-m semi-arid elevational gradient in the southwestern United States, we test whether flowering phenology diverged among subpopulations within species and among five communities comprising 590 species. Applying circular statistics to test for changes in year-round flowering, we show flowering has become earlier for all communities except at the highest elevations. However, flowering times shifted at different rates across elevations likely because of elevation-specific changes in temperature and precipitation, indicating diverging phenologies of neighboring communities. Subpopulations of individual species also diverged at mid-elevation but converged in phenology at high elevation. These changes in flowering phenology among communities and subpopulations are undetectable when data are pooled across the gradient. Furthermore, we show that nonlinear changes in flowering times over the 33-year record are obscured by traditional calculations of long-term trends. These findings reveal greater spatiotemporal complexity in phenological responses than previously recognized and indicate climate is driving phenological reshuffling across local spatial gradients. • Flowering time is diverging among communities across an elevational gradient • Divergence reflects nonlinear shifts in flowering phenology over three decades • Climatic variables have also changed differently across space and over time • Changing climate is driving phenological reshuffling across local spatial gradients Using 33 years of data, Rafferty et al. test whether flowering times have diverged for neighboring communities comprising 590 species across an elevational gradient. Divergent and nonlinear shifts in flowering time are related to elevation-specific changes in temperature and precipitation and will likely alter species interactions and gene flow. [ABSTRACT FROM AUTHOR]

Species interactions, such as those between plants and pollinators, are known to be shaped by both evolutionary history and ecological factors. However, little is known about how multiple factors (e.g. phylogeny, phenology, abundance and functional traits) interactively affect interaction patterns.Using a plant–bumblebee network comprising 2,428 interactions between 29 plant species and 12 bumblebee species in the Himalaya–Hengduan Mountains, we tested for phylogenetic signal and whether phylogenetic pattern was explained by abundance, phenology and 13 plant and bumblebee functional traits. We also tested whether trait matching in two pairs of plant–bumblebee traits explained interaction frequencies at both species and individual levels.The network showed significant phylogenetic signal; closely related bumblebees tended to visit similar sets of plants, but not vice versa. Among all the measured factors, nectar volume and sugar concentration, rather than other phylogenetically constrained factors, were most important for explaining phylogenetic pattern (64% and 54% respectively). Although long–tongued bumblebee species tended to interact with long–tubed flowers, trait matching did not predict short–tongued bee interaction frequencies. Despite this, trait matching was apparent at the level of individual bees, reflecting intraspecific variation in tongue length and body size. Different selection pressures may exist within this bumblebee community, resulting in specialized, co–evolved traits in long–tongued species and adaptive generalization in short–tongued species to gain access to a variety of flowers.Together, these findings contribute to our understanding of phylogenetic trait–based structure in species interaction networks. In particular, this study provides new evidence for the importance of nectar rewards in structuring interaction patterns in pollination mutualisms. The results also demonstrate that trait matching may occur at the individual level, despite not being detectable at the species level, and underline the necessity of taking intraspecific trait variation into account in studies of community structure. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Synchrony defines an organism's overlap with potential resources and mates, essential for survival and reproduction. Flowering synchrony influences gene flow within species and patterns of interaction among plants and with other trophic levels, including pollinators. Climate‐change driven shifts in plant phenology may disrupt plant–plant and plant–pollinator interactions, resulting in reshuffling of communities and altered ecosystem processes. We present a unique long‐term metacommunity‐wide study relating changes in flowering synchrony within and among species along an elevational gradient to changes in local climatic conditions. We apply a circular statistical method that estimates flowering phenology overlap between entire flowering distributions, overcoming limitations and biases of single indicators such as first and last flowering dates. We analyzed more than 300 000 flowering overlap estimates between 217 species in five plant communities across a 1267 m gradient over four decades (1984–2019) in the southwestern USA. We show that co‐flowering synchrony significantly decreased in all plant communities, with a maximum of 28.1% of synchrony lost at the lowest elevations. Decreased synchrony was significantly negatively correlated with increasing temperatures recorded across the gradient. Reduced precipitation had locally‐dependent effects and, in combination with warmer temperatures, accelerated the decrease in synchrony, especially at the lowest elevations. Flowering synchrony within plant species occurring in multiple communities increased between most community pairs, with a maximum increase of 30.5%, and at accelerated rates in recent years. The exception, likely associated with differences in topography, was a 5.6% decrease in synchrony between the two highest‐elevation communities. Overall, increased synchrony within species occurring at multiple elevations indicates homogenization of flowering phenology across the gradient. These results show significant reshaping of flowering synchrony within and between plant communities in response to changing climate. Because plant phenology influences many ecological processes, such fundamental changes may have far‐reaching and negative effects on ecosystem stability. [ABSTRACT FROM AUTHOR]