Exploring sex-specific anatomical adaptations in Rhamnus alaternus L. a Mediterranean dioecious shrub: implications for resilience to climate change

Secondary sexual dimorphism plays an important role in shaping the response of plants to different environmental constraints, particularly in relation to energy requirements. Dioecious plants exhibit intricate sex-specific differences that influence stress tolerance mechanisms. In Mediterranean ecosystems, the challenges to stress tolerance are exacerbated by climate change-induced changes in temperature, precipitation patterns and frequency of extreme weather events. Understanding how male and female dioecious plants cope with stress is essential for the development of effective conservation strategies. This study focuses on the investigation of secondary sexual dimorphism in the wood and leaf anatomy of a Mediterranean shrub Rhamnus alaternus L., to identify potential sex-specific responses to environmental stressors. We conducted a comprehensive analysis of wood and leaf anatomy in male and female individuals at a southern Italian Mediterranean site. Microscopy and subsequent image analysis allowed the quantification of anatomical features related to water-use efficiency, safety against embolism and photosynthetic efficiency. Parameters measured included stem vessel size and distribution, reaction wood formation, stomata characteristics, leaf tissue thickness and mesophyll density. Our results show a coordinated sex-specific adaptation in anatomical traits that influence either the efficiency or safety of water flow and the regulation of gas-exchange. This knowledge is crucial for improving the resilience and diversity of these plant populations in the face of climate change impacts. The knowledge gained from this study will contribute to the development of targeted conservation strategies for dioecious species in Mediterranean ecosystems.