2026/01/01 by Andrea E. Berardi, José Carlos del Valle, Matthew H. Koski +2 · 1 voice
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Plant and animal studies #Plant Gene Expression Analysis #Plant Reproductive Biology
paper · pdf · doi:10.1002/ajb2.70150
Flower color plays a central role in pollination, functioning as one of the major traits attracting pollinators. The close relationship between flower color phenotypes and pollination has been studied extensively, and we are still learning about the intricacies of the role of flower color in plant–pollinator relationships. However, there are also other alternative, complementary, and important functions that flower color plays a role in, often due to alternative functions of pigments behind the color, the traits that are tightly correlated with flower color, or structural epidermal changes. For example, many of the flavonoid-based pigments (including anthocyanins) in plants function as antioxidants or provide protection against extreme temperatures, drought, UV radiation, pathogens, herbivores, and other selective agents. These additional pigment functions may explain the current distribution of flower colors across environmental gradients and may have important consequences when interpreting plant adaptations to pollinators and their environment, particularly in the face of rapid and ongoing changes in climate globally (Koski et al., 2020; Sullivan et al., 2021; Lacey, 2025). Carotenoids and betalains, the other major groups of flower pigments, also have antioxidant activity, although their protective roles in flowers are less well characterized. The purpose of this special issue is not to question or diminish the role of pollinators in flower color diversity, but rather to highlight the alternative, complementary, and even antagonistic roles, selective pressures, and macroevolutionary patterns that can shape flower color—reflecting an emerging paradigm shift in how we study and understand floral color. The articles in this special issue cover a broad range of approaches to study and assess flower color in the field, greenhouse, and laboratory including biochemical quantification, reflectance spectra, photography, physics, modeling, citizen-science databases, and herbarium collections. The research in this special issue helps to expand our understanding of the forces shaping flower color, revealing complex interplays between biotic partners, abiotic conditions, and intrinsic physiological and macroevolutionary correlations and constraints. For example, Sinnott-Armstrong et al. (2026) link macroevolutionary patterns of flower and fruit color across lineages, and Dellinger et al. (2025) challenge a long-standing paradigm that flower colors are primarily molded by animal visual systems, instead highlighting that flowers and fruits often experience distinct suites of abiotic selective pressures. This shift toward a more integrative framework is echoed by studies demonstrating environmentally and ecologically mediated divergence. Camargo et al. (2026) show how both biotic and abiotic factors drive the diversification of color traits across the mosaic landscapes of the campo rupestre (rupestrian grassland) in Brazil, and Jaeger et al. (2025) tested whether a heritable flower color polymorphism generated by the relatively understudied betalain pigments is driven by ecological trade-offs and climactic variables. Labin et al. (2025), Fetterly et al. (2025), and Grossenbacher et al. (2025) each used broad geographical samplings to link abiotic gradients to within-species flower color polymorphism, demonstrating how soil chemistry, climate, habitat structure, and pollinator behavior interact to drive intraspecific variation in this trait. Mechanistic approaches can be used to investigate how environmental conditions modify the production and perception of color. For example, De Paola and Veldhuis et al. (2025) demonstrate that floral brightness can depend more on mesophyll light scattering than on epidermal structures, and Narbona et al. (2025) show that heat stress alters pigment profiles, UV reflectance, and thermal tolerance, without diminishing pollinator attractiveness. Watts et al. (2026) compared the observed and theoretical floral color space, finding that not all possible colors are realized in nature and that there are evolutionary constraints concerning the mechanisms shaping floral color diversity. Finally, Lacey (2025) comprehensively reviewed temperature-driven evolution of flower color, and Apland et al. (2025) assessed how floral color modifies the temperature of the floral microenvironment. A consistent picture emerges across the articles in this special issue: Flower (and fruit) color is shaped across micro- and macroevolutionary scales not only by interactions with pollinators, but also by a wide array of biotic and abiotic pressures. This special issue was inspired by the outstanding contributions to the “Paradigm Shifts in Flower Color” Symposium at the XX International Botanical Congress held in Madrid, Spain, on 25 July 2024. As the special issue editors, we are grateful to the authors and reviewers who worked together on this special issue on flower color for AJB. Andrea E. Berardi: Writing—original draft; Writing—review and editing. José Carlos del Valle: Writing—review and editing. Matthew H. Koski: Writing—review and editing. Eduardo Narbona: Writing—review and editing. Justen Whittall: Writing—review and editing.