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Abstract BackgroundPollinators impose strong selection on floral traits, but other abiotic and biotic agents also drive the evolution of floral traits and influence plant reproduction. Global change is expected to have widespread effects on biotic and abiotic systems, resulting in novel selection on floral traits in future conditions. ScopeGlobal change has depressed pollinator abundance and altered abiotic conditions, thereby exposing flowering plant species to novel suites of selective pressures. Here, we consider how biotic and abiotic factors interact to shape the expression and evolution of floral characteristics (the targets of selection), including floral size, colour, physiology, reward quantity and quality, and longevity, amongst other traits. We examine cases in which selection imposed by climatic factors conflicts with pollinator-mediated selection. Additionally, we explore how floral traits respond to environmental changes through phenotypic plasticity and how that can alter plant fecundity. Throughout this review, we evaluate how global change might shift the expression and evolution of floral phenotypes. ConclusionsFloral traits evolve in response to multiple interacting agents of selection. Different agents can sometimes exert conflicting selection. For example, pollinators often prefer large flowers, but drought stress can favour the evolution of smaller flowers, and the size of floral organs can evolve as a trade-off between selection mediated by these opposing actors. Nevertheless, few studies have manipulated abiotic and biotic agents of selection factorially to disentangle their relative strengths and directions of selection. The literature has more often evaluated plastic responses of floral traits to stressors than it has considered how abiotic factors alter selection on these traits. Global change will likely alter the selective landscape through changes in the abundance and community composition of mutualists and antagonists and novel abiotic conditions. We encourage future work to consider the effects of abiotic and biotic agents of selection on floral evolution, which will enable more robust predictions about floral evolution and plant reproduction as global change progresses. 

With continually increasing summer temperatures and intense heat waves, it can be easy to neglect the ecological effects of winter climate change. However, shifts in the climate during winter can have profound consequences for eco-evolutionary dynamics in extratropical latitudes and high-elevation locales. Climate change has increased winter temperatures, disrupted snowpack, and reduced ice cover (Rixen et al., 2022). Extreme losses of snowpack are projected for many regions by the end of the century (Talsma et al., 2022). Patterns of climate change are complex and region dependent, but winters are becoming less reliable overall, with elevated temperatures and altered snow dynamics. In ecosystems with cold winters, many plant species require exposure to low, but not necessarily freezing, temperatures for a prolonged period to break dormancy in the spring; this chilling requirement prevents leaf emergence, flowering, or germination from occurring in the middle of winter (Chuine et al., 2016). Warming winters have advanced the onset of spring and could result in insufficient overwinter chilling. In addition, spring and fall frosts that occur after plants become physiologically active can perturb phenology and reduce fitness. Finally, novel winter climates could disrupt biotic interactions among plants, their mutualists, and antagonists. Here, I discuss emerging research frontiers in these domains.