Trait variation between and within Andes and coastal mountain ranges in the iconic South American tree Araucaria araucana in Chile

A major barrier globally to achieving restoration goals is the identification and production of appropriate plant materials. To produce high-quality plant materials for restoration success, prevent negative consequences to plant populations, and conserve genetic diversity, it is critical to understand ecotypic variation among plant populations, especially in relation to environmental conditions. For Araucaria araucana, a highly threatened iconic South American tree that grows across a substantial climate gradient, this information is urgently needed to guide restoration and conservation efforts. We conducted a common garden experiment using seedlings from 12 populations of A. araucana across its range in Chile. This approach allowed us to assess regional (coastal versus Andes mountain ranges) and population-level variation in plant traits and relate this variation to environmental variables. Our results demonstrate that A. araucana exhibits differentiation at both regional and population levels, particularly in traits such as branch number and length (indicative of plant architectural differences) and needle width (reflecting variation in leaf investment). This variation is at least partly explained by climate variables, with the most significant differences attributed to regional variations in temperature annual range and mean vapor pressure deficit. Based on these findings, we recommend restoration efforts prioritize conserving genetic variation both among and within regions and their populations, while avoiding translocations of genotypes between coastal and Andes populations.