Drought and light anatomical adaptive leaf strategies in three woody species caused by microclimatic selection at "Evolution Canyon", Israel

Seven structural and morphological characteristics of leaves from three woo dy species (Olea europaea, Ceratonia siliqua, and Pistacia lentiscus) were quantified for trees and shrubs from "Evolution Canyon", Lower Nahal Oren m icrosite, Mount Carmel, Israel. Our results indicate overall parallel and s pecies-specific leaf xeromorphic interslope microclimatic adaptations. Leav es of all three species from the south-facing slope (SFS) were smaller than those from the north-facing slope (NFS). Leaves of O. europaea and C. sili qua on the SFS were significantly thicker than those on the NFS due to incr eased thickness of the two photosynthetic parenchyma layers, the palisade a nd spongy layers. A similar significantly increased thickness of the spongy layer was found in leaves of P. lentiscus. The opposite trend was found in the palisade layer thickness of this species. Thicker epidermis was found in SFS as compared to NFS leaves of O. europaea and P. lentiscus, while the reverse was found in C. siliqua. Palisade cells in SFS leaves of C. siliqu a and P. lentiscus were significantly longer than in leaves from the NFS, w hile the opposite trend was found in O. europaea. Discriminant analysis suc ceeded in differentiating significantly between material collected from sev en stations for the three species. The results suggest microscale morpholog ical adaptations against drought on the more arid SFS, caused presumably by climatic selection.