Changes in foliar traits through environmental gradients in two Mediterranean Quercus species and their hybrids.

Introduction:

We analyzed several leaf morphological traits of two Quercus species widely distributed in the Iberian Peninsula (Q. faginea and Q. pyrenaica) and their hybrids, under contrasting environmental conditions, to determine differences between groups, if they are consistent in the different climatic zones and whether they could confer an advantage to any of the groups in the new predicted climate scenario.

Methods:

This study was carried out in three areas located in the central-west of Spain; in each area, three plots relatively close to each other were selected: one with apparent dominance of Q. faginea, another with dominance of Q. pyrenaica and intermediate zones with both species. In each plot, 10 specimens of the supposedly dominant category in each case were selected, after having been categorized using AFLPs. From each of the 90 specimens, leaf samples were taken and used for morphological analysis, including a total of 18 different traits.

Results:

Only three traits revealed discriminant value between the three genetic groups (leaf weight per unit area, maximum width of the blade and depth of lobes), with the hybrids showing greater proximity to Q. faginea for the rest of the characteristics and consistent results in the different study areas. In all three groups, the leaves tend to be larger, with larger petioles and a greater number of and deeper lobes in the area where temperatures are higher.

Conclusions:

Contrary to what was expected, it was not the hybrids that showed the greatest variability between areas, but rather the Q. faginea individuals that showed the greatest capacity to modify these traits in response to the different climatic conditions between study areas, which, together with their characteristic foliar traits (greater weight per unit area, smaller leaf size and shorter petioles), could determine a greater probability of persistence in the face of climate change.