The role of population origin and microenvironment in seedling emergence and early survival in Mediterranean maritime pine (Pinus pinaster Aiton)

Abstract

Understanding tree recruitment is needed to forecast future forest distribution. Many studies have reported the relevantecological factors that affect recruitment success in trees, but the potential for genetic-based differences in recruitment hasoften been neglected. In this study, we established a semi-natural reciprocal sowing experiment to test for local adaptationand microenvironment effects (evaluated here by canopy cover) in the emergence and early survival of maritime pine (Pinuspinaster Aiton), an emblematic Mediterranean forest tree. A novel application of molecular markers was also developed totest for family selection and, thus, for potential genetic change over generations. Overall, we did not find evidence tosupport local adaptation at the recruitment stage in our semi-natural experiment. Moreover, only weak family selection (ifany) was found, suggesting that in stressful environments with low survival, stochastic processes and among-year climatevariability may drive recruitment. Nevertheless, our study revealed that, at early stages of recruitment, microenvironmentsmay favor the population with the best adapted life strategy, irrespectively of its (local or non-local) origin. We also foundthat emergence time is a key factor for seedling survival in stressful Mediterranean environments. Our study highlights thecomplexity of the factors influencing the early stages of establishment of maritime pine and provides insights into possiblemanagement actions aimed at environmental change impact mitigation. In particular, we found that the high stochasticityof the recruitment process in stressful environments and the differences in population-specific adaptive strategies maydifficult assisted migration schemes.