Cyclical drought and herbivore threats are potential causes of leaf variegation dimorphism in <i>Cypripedium forrestii</i>

Abstract Leaf variegation, the mosaic of colors on the leaf surface, can be developed by certain plant species without external influence. Although it may be associated with a variety of functions, the stable existence of different leaf color morphs within a plant species has not been fully explained by previous studies. This study focuses on the two leaf morphs of Cypripedium forrestii, an endangered lady slipper orchid, and compares their micromorphological structure, photosynthetic potential, differentially expressed genes (DEGs), and ecological features to gain a comprehensive understanding of the underlying leaf variegation polymorphism. Our findings demonstrate that leaf variegation is not pathological and does not affect photosynthetic potential. Additionally, it significantly reduces herbivory damage. We found that the probability of herbivory and leaf area loss for variegated leaves was notably higher under drought conditions. Therefore, variegated individuals may be more adaptive under such conditions, while non-variegated ones may be more cost-effective in normal years. These results suggest that different leaf color morphs may be favored by varying environmental conditions, and leaf polymorphism may be a legacy of ancient climate and herbivore fluctuations.