3.2 | Phenotypes
Phenotypic values of the eight morphological traits of leaves and shoots were obtained from the 224 sampled trees in the inland and coastal sites (Data S1). PCA for the eight traits summarized the first and second PCs that contributed to 45.2% and 16.7%, respectively, of phenotypic variation (Figure 3a). All the eight traits positively affected the first PC, which represented Qd -like phenotypes (Figure 3a). Among the eight traits, four leaf traits (relative leaf width, lateral vein interval, tooth angle, and stellate hair length), namely taxon-specific traits, negatively affected to the second PC. Another two leaf and two shoot traits (stellate hair density, LMA, shoot diameter, and scale bud number), namely habitat-specific traits, positively affected the second PC.
In both sites, Qc , Qa , and Qd trees showed lower, intermediate, and higher first PC values, respectively (P< 0.001), and Qa and Qd trees showed higher and lower second PC values, respectively (P < 0.001; Figure 3b, c). Thus, coastal Qa trees mainly differed from inlandQc trees in the habitat-specific traits, while Qa trees mainly differed from Qd trees in the taxon-specific traits. Overall, both taxon-specific and habitat-specific traits contributed to phenotypic variation between Qc and Qd , which was represented by the first PC.
Relationship between the Qd ancestry and the first phenotypic PC value differed between the sites, indicating phenotypic plasticity (Figure 4). The first phenotypic PC value was increasing with theQd ancestry (β1 = 4.35, P < 0.001) and higher in the coastal sites than in the inland site (β2 = 2.20, P < 0.001). A slope of the first phenotypic PC value to the Qd ancestry was more gentler in the coastal site than in the inland site (γ = –1.97, P< 0.001), indicating larger phenotypic response of Qatrees than in Qd trees to coastal environment.