Geographical variation in growth form traits in Quercus suber and its relation to population evolutionary history

Differential selection pressures caused by environmental disparities lead to populations to become differentiated as they adapt to local environments. In addition, natural selection during the species past can contribute to the observed differentiation. In this study, we examine the geographic variation in a set of four traits related to growth and plant architecture in cork oak (Quercus suber) and investigate to what extent this variation is the result of the effects of ongoing evolution in current environments and the past evolutionary history of the species. Cork oak saplings at the common garden trial exhibited differences in plant architecture associated to cpDNA lineage. Eastern lineages, exhibited the lowest apical dominance and highest branchiness, consistent with the analyses in other cork oak trials. In contrast, patterns linked to the evolutionary past were less evident in height and diameter. These results suggest that selective pressures after cpDNA divergence can have blurred patterns in some traits closely related to fitness, while conserving the past evolutionary imprints in plant architectural traits. Introgressed populations did not show significant differentiation in architecture, which suggests that allele exchanges via hybridization have had a limited effect on population differentiation in cork oak. Finally, populations within lineages also showed differences in growth and architecture. Correla- tion between population architecture and temperature patterns were observed indicating that environmental factors such as climate also could result crucial in the evolution of plant architecture of cork oak within lineages