Evolutionary Ecological Drivers of External Tree Bark Macromorphology in Temperate Ecosystems

Abstract The study of bark morphology reveals significant although not absolute relationships between bark types, tree species, and their environmental conditions. This paper aims to review the inter- and intraspecific ecological and evolutionary drivers that seem to have shaped the macromorphological features of bark, especially in temperate forest ecosystems and especially in Europe. Extensive literature research shows that various factors influence bark thickness, structure, color, and morphology, including solar radiation, climate, adaptation to various disturbance regimes, site conditions and biotic factors, reflecting together long-term selective pressures during evolution. Bark’s simultaneous multiple functions and its ontogenetic changes often complicate the identification of the individual selective agents of the adaptive mechanisms and morphologies. An evolutionary perspective can clarify why certain bark types are common in specific environments, how some traits persist as secondary functions, or why diverse bark forms coexist not only in the same site, but also in various ontogenetic stages and positions of the same individuals. Intraspecific variation shaped by both genetic and environmental influences often results in phenotypic plasticity, enhancing species’ environmental and age/size related adaptability. We suggest that further research examine current and historical climate, site, and biotic conditions to understand their influence on bark structure and morphology.