Integrating intraspecific trait variation and spatiotemporal variability of selection as levers of action in forest management

Adaptation is a polysemous word referring both to the state of being adapted and to the selection processes leading to this state. However, considering population adaptation only as an ultimate achievement in a static rather than dynamic perspective may lead to a double misperception: (i) that all adapted populations have depleted variation of adaptive traits and, therefore, low evolvability, and (ii) that adaptation systematically requires many generations. This static vision of adaptation as an achievement is particularly inappropriate for long-lived organisms like trees that continuously respond to selection and retain high levels of adaptive trait variation. This review proposes a baseline for a process-based approach of adaptation in trees, shedding new light on current challenges for forest management and forest genetic resources conservation in the context of global change.A first general section uses the genes-traits-fitness mapping framework to explore the effect of selection on different types of traits, depending on their links to other traits and fitness. In a second section, trait variation and coordination patterns observed in forest trees are interpreted in terms of biological constraints and response to selection. A third section investigates, for trees, how the genes-traits-fitness map varies in space and time with environmental conditions and developmental stages, resulting in spatiotemporal variability of selection. A fourth section reviews the impacts of forestry interventions on trait variation and selection. The conclusive section illustrates the integration of selection as a dynamic and partly manageable process in management thinking for forest genetic resource sustainable use and conservation.