Sainsbury Laboratory, University of Cambridge Cambridge, England, United Kingdom
Body of Abstract: Angiosperms show a wide diversity of petal patterns that differ in pigmentation, shape and cuticular ornamentation of epidermal cells. Some striking pattern examples include Gazania petal stripes, Veronica venations and the bullseye pattern of the poached egg plant Limnanthes douglasii. These patterns function to attract pollinators to the flower and guide them to the pollen and nectar rewards but can also be involved in mimicry, act as anti-herbivory signals or participate in protection against UV or water loss reduction. Our lab has developed an herbaceous species of Hibiscus as a new model system to investigate the molecular mechanisms responsible for the formation and evolution of these patterns. Hibiscus trionum, also known as flower-of-an-hour, has a bullseye pattern with a purple centre and white margin. It belongs to a species complex that underwent a recent radiation event and display a range of petal pattern variation between species and populations. We employed phylogenetic and molecular techniques to solve the species relationships across the Trionum complex, identified key genes involved in the establishment of a bullseye pattern and started to uncover some of the molecular events accounting for pattern variation. We found that bullseye reduction occurred multiple times independently across the Trionum complex via reduction of pigment production due to repeated modifications of a single genetic locus, representing an example of convergent evolution. We also found that buff-tailed bumblebees (Bombus terrestris) were capable of distinguishing between bullseyes of different sizes and showed preference for specific pattern proportions. In addition to improving our understanding of the mechanisms underpinning natural diversity, our results can inform strategies to improve flower salience and manipulate plant-pollinator interactions.