Supergene solves evolutionary puzzle of mirror-image flowers
The left-right asymmetry of South African butterfly lilies (genus Wachendorfia) has been regarded as a classic evolutionary puzzle for more than a century. Due to the mirror-image arrangement of the floral parts, the plants achieve efficient cross-pollination. The molecular basis of this arrangement has now been uncovered by an international team led by the University of Potsdam.
South African butterfly lilies, belonging to the genus Wachendorfia, have long puzzled scientists with their mirror-image arrangement of floral parts, which enables efficient cross-pollination. An international team led by the University of Potsdam has now unraveled the molecular basis behind this unique trait. The researchers discovered that a supergene, containing two key factors, determines whether Wachendorfia plants consistently develop styles and stamens bent to the left or right.
These factors work together tightly to ensure pollen is deposited in specific positions on pollinator bodies, allowing the respective mirror-image floral form to pick it up again. This supergene coupling of style and stamen orientation is so precise that the plants remain reliant on cross-pollination, promoting genetic diversity.
Mechanical models and cultivation experiments showed that both rotation and gravity-guided growth are necessary for the pronounced asymmetry observed. The left and right directions are relative to gravity, not internal body axes. Using cultivated Wachendorfia thyrsiflora from the Botanical Garden of the University of Potsdam, the team conducted cell-biological investigations.
This collaborative study, involving fieldwork in South Africa, theoretical modeling, and genomic and cell-biological analyses, highlights the importance of supergenes in coordinating multiple traits. Understanding such systems sheds light on how plants program their pollinators precisely, driving speciation and ecological adaptation.
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