Leaf dimorphism in Cupressus nootkatensis D. Don and Cupressus vietnamensis (Farjon & T.H. Nguyên) Silba (Cupressaceae) and its ecological and evolutionary significance

Abstract Key message We examined the leaf structure of two basal Cupressus species with a distinct dimorphism. Some foliar features are regarded as ancestral and it is suggested that drought adaptation was one important ecological drivers in evolution genus. Leaf morphology anatomy species, C . nootkatensis vietnamensis , were investigated classical paraffin technique scanning electron microscopy (SEM). Like all these characterised by dramatic change foliage. Juveniles have needle leaves first before they abruptly to mature scale type. In needle-leaved shoots occur next scale-leaved ones even on trees, which unique among today´s species. Adults develop only throughout. both taxa, show dimorphism between lateral facial leaves, arranged flat spray; foliate two-dimensionally flattened. These several xeromorphic features; e.g. strongly reduced size, stomata high, collar-like Florin rings, presence hypodermis continuous layer well-developed transfusion tissue. The type found Cunninghamia member Cupressaceae so condition derived one. Scale members cupressoid clade within taxa from mesic habitats. However preadaptation survival under xeric conditions likely an evolutionary driver radiation into arid environments, has also been case genera such Callitris.