In the intricate world of floral evolution, the seemingly simple patterns on petals carry profound secrets about genetics, environment, and pollinator interactions. A groundbreaking new study from the Sainsbury Laboratory at the University of Cambridge sheds light on this complexity by uncovering the genetic basis behind the repeated disappearance of visually striking bullseye patterns in Hibiscus flowers. Contrary to the expectations set by pollinator preferences, several Hibiscus species have independently evolved to lose these eye-catching markings, prompting scientists to delve deep into underlying genetic mechanisms that drive such counterintuitive changes.
The bullseye pattern in many flowering plants acts as a visual beacon, guiding pollinators to the flower’s reproductive structures and thereby enhancing the efficiency of pollination. Bumblebees, in particular, have shown a clear preference for Hibiscus flowers exhibiting large, dark bullseyes on their petals, suggesting a strong selective advantage for these patterns in attracting effective pollinators. Yet, ironically, this attractive floral feature has been lost in multiple Hibiscus lineages that evolved under varying ecological conditions. This paradox raised key questions about the evolutionary pressures and genetic changes that propel such losses despite demonstrable pollinator benefits.
The research reveals that this repeated loss of bullseye patterns is driven by parallel genetic modifications converging on a single critical gene, named BERRY1. This gene plays a central regulatory role in the synthesis of anthocyanins, the pigments responsible for the purple and dark hues of the bullseye spots. Through detailed phylogenetic and molecular analyses, the research team uncovered that different Hibiscus species exhibit independent mutations or deletions in BERRY1. For instance, in Hibiscus richardsonii, mutations disrupt the gene’s function, leading to reduced anthocyanin production and thus smaller bullseye patterns. In contrast, Hibiscus verdcourtii shows a complete deletion of BERRY1, resulting in a total absence of these petal markings.
These findings exemplify the phenomenon of convergent evolution, where similar traits—or in this case, similar trait losses—arise independently in different species through repeated changes in the same gene. This convergence highlights the evolutionary flexibility of floral traits and underscores how single genetic elements can have outsized impacts on phenotypic diversity. The repeated targeting of BERRY1 across species also provides a compelling model for understanding how biodiversity can be molded by both stochastic genetic changes and selective forces acting in diverse ecological contexts.
Interestingly, the study does not stop at describing genetic alterations but also explores the ecological and environmental factors that might favor the loss of bullseye patterns. While the visual cues clearly optimize attraction to bumblebees, shifts in pollinator communities or environmental variables such as ultraviolet (UV) radiation exposure may exert opposing selective pressures. Bullseyes have been documented in other species to offer protection to pollen grains against UV damage. Thus, changes in habitat UV levels or pollinator types could tip the evolutionary balance against maintaining large bullseyes, catalyzing pattern reductions or loss despite their attractiveness to longstanding pollinators.
Furthermore, the discovery of BERRY1 as a key regulator invites broader reflections on the genetic architecture of floral traits. The gene’s central role in pigment biosynthesis suggests that relatively simple mutations—such as deletions or disruptions—can precipitate considerable phenotypic shifts. This contrasts with the traditionally held view that complex traits require complex genetic rewiring. Instead, the Hibiscus case illustrates how evolution can harness modular genetic elements to generate rapid and parallel evolutionary outcomes, contributing to overall adaptive radiation and species diversification.
The researchers also employed a detailed phylogenetic framework to map bullseye pattern variation across several closely related species within the Hibiscus trionum complex. This analysis revealed a gradation of pattern size and intensity, from the robust, large purple bullseyes seen in Hibiscus trionum to the subtle, diminutive rings in Hibiscus richardsonii, culminating in their complete absence in Hibiscus verdcourtii. Such gradation suggests a continuum of intermediate genetic states and offers a living snapshot of evolutionary trajectories at different stages of pattern loss.
This continuum and the associated genetic underpinnings not only illustrate the microevolutionary processes shaping petal pigmentation but also reinforce the importance of integrating genetic, ecological, and evolutionary perspectives to fully understand floral diversification. The detailed experimental design, combining genomics, gene function assays, and pollinator behavior observations, sets a new standard for investigating how single-gene mutations can cascade into substantial ecological effects in plant reproduction.
The work is published in the esteemed journal New Phytologist and signals a potentially transformative chapter in plant evolutionary biology. Beyond its scientific merit, the study carries practical implications, especially for agriculture and conservation. Understanding how floral traits evolve in response to pollinator preferences and environmental pressures can guide plant breeding programs aiming to enhance pollinator attraction and efficiency, thereby supporting biodiversity and crop productivity in changing environmental scenarios.
Capturing public imagination, the research is currently being showcased at the Royal Horticultural Society Chelsea Flower Show in London, where the team presents live imaging and scanning electron microscope visuals of Hibiscus flowers exhibiting contrasting bullseye patterns. This innovative public engagement elevates awareness of how fundamental plant biology research can illuminate the evolutionary narratives shaped by genetics and environment.
Looking forward, the study’s authors emphasize that their findings open exciting avenues for future research exploring the interplay between genetic mutations, ecological dynamics, and the environmental landscape—a multilayered puzzle critical to deciphering how biodiversity thrives and adapts in nature. The repeated, independent evolution of bullseye loss within a single complex not only reveals the power of genetic hotspots but also challenges scientists to reconsider the pathways through which flowers visually communicate with the animal world.
In the end, the Hibiscus bullseye story is a remarkable tale of nature’s genetic artistry, where the loss of a visually striking trait is not a mere absence but a vibrant evolutionary signal—one that merges genotype, phenotype, and environmental interplay into a mosaic painting the diverse tapestry of life.
Subject of Research: Cells
Article Title: The genetic basis of replicated bullseye pattern reduction across the Hibiscus trionum Complex
News Publication Date: 21-May-2025
Web References:
https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.70168
References:
May T. S. Yeo, Alice L. M. Fairnie, Valentina Travaglia, Joseph F. Walker, Lucie Riglet, Selin Zeyrek, and Edwige Moyroud (2025) The genetic basis of replicated bullseye pattern reduction across the Hibiscus trionum Complex, New Phytologist.
Image Credits: May Yeo et al
Keywords: Developmental genetics
