Leaf anatomical diversity in subfamily Dryadoideae (Rosaceae): taxonomic significance at the generic level

• Unique leaf anatomical characters were identified across all genera of the subfamily Dryadoideae • Dryadoideae has a high diversity of trichomes that had not been fully described previously • Cercocarpus is unique within the Dryadoideae exhibiting stomatal crypts • The leaves of Chamaebatia were thought to be compound, but they are actually simple • Dryas exhibits eglandular, dendritic, multicellular trichomes, which are extremely rare within the Rosaceae family Dryadoideae (Rosaceae) comprises the genera Cercocarpus, Chamaebatia, Dryas , and Purshia . Despite its taxonomic value, the foliar anatomy of this subfamily has not been studied or compared between genera. The objective was to characterize and identify qualitative leaf anatomical traits that allow diagnosis of genera and compare them with other Rosaceae. Transverse and paradermal sections were prepared from 32 species and analyzed using light microscopy. Each genus exhibited a unique combination of traits. Cercocarpus showed stomatal crypts and an abaxial hypodermis. Chamaebatia displayed S-undulated anticlinal epidermal walls and fibers above the phloem. It also showed glandular trichomes with a multiseriate stalk and vascular tissue at the base. Additionally, the mesophyll was reduced and continuous, supporting simple leaves in Chamaebatia , a trait not previously recognized in this genus. Purshia showed glandular trichomes with a multiseriate stalk on the adaxial surface, less developed spongy parenchyma and palisade parenchyma in the midvein. In Dryas eglandular multicellular trichomes were found on the abaxial surface, and a sunken adaxial midvein. Other informative characters included mesophyll type, idioblasts, and secondary growth in the midvein. Although some intrageneric variation was observed, anatomical traits were generally consistent within genera. These findings provide the first comprehensive anatomical framework for Dryadoideae and highlight the taxonomic value of leaf anatomy. The results contribute with novel characters for genera, and offer their integration into future phylogenetic and evolutionary studies within Rosaceae.