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Abstract BackgroundThe frequency and intensity of droughts are expected to increase under global change, driven by anthropogenic climate change and water diversion. Precipitation is expected to become more episodic under climate change, with longer and warmer dry spells, although some areas might become wetter. Diversion of freshwater from lakes and rivers and groundwater pumping for irrigation of agricultural fields are lowering water availability to wild plant populations, increasing the frequency and intensity of drought. Given the importance of seasonal changes and extremes in soil moisture to influence plant reproduction, and because the majority of plants are flowering plants and most of them depend on pollinators for seed production, this review focuses on the consequences of drought on different aspects of reproduction in animal-pollinated angiosperms, emphasizing interactions among drought, flowering and pollination. ScopeVisual and olfactory traits play crucial roles in attracting pollinators. Drought-induced floral changes can influence pollinator attraction and visitation, together with pollinator networks and flowering phenology, with subsequent effects on plant reproduction. Here, we review how drought influences these different aspects of plant reproduction. We identify knowledge gaps and highlight areas that would benefit from additional research. ConclusionsVisual and olfactory traits are affected by drought, but their phenotypic responses can vary with floral sex, plant sex, population and species. Ample phenotypic plasticity to drought exists for these traits, providing an ability for a rapid response to a change in drought frequency and intensity engendered by global change. The impact of these drought-induced changes in floral traits on pollinator attraction, pollen deposition and plant reproductive success does not show a clear pattern. Drought affects the structure of plant–pollinator networks and can modify plant phenology. The impact of drought on plant reproduction is not always negative, and we need to identify plant characteristics associated with these more positive responses.
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The effect of global change on the expression and evolution of floral traits
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.
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- Award ID(s):
- 2220927
- PAR ID:
- 10504689
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Annals of Botany
- ISSN:
- 0305-7364
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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