Abstract:

To clarify the phenotypic diversity and variation patterns of major wild tree peony resources in the Qinling and Ziwuling regions of Shaanxi Province，eight natural populations representing Paeonia rockii，P. jishanensis，P. qiui and P. ostii（two populations each）were investigated. Twenty phenotypic traits of leaves，flowers and fruits were measured and analyzed using nested ANOVA，Shannon diversity index and two-way hierarchical clustering. The results showed：（1）Nineteen traits，except seed diameter，exhibited highly significant interspecific differences；width of a binate leaf and filament length differed significantly among populations，while fruit pod width differed significantly within populations. The mean phenotypic differentiation coefficient（VST）was 55.76%，indicating that phenotypic variation is mainly driven by genetic differentiation.（2）Across the four species，the Shannon phenotypic diversity index（H）ranged from 1.55 to 1.68 and the coefficient of variation（CV）from 10.44% to 17.38%，consistently revealing abundant phenotypic variation with P. rockii showing the highest diversity.（3）Two-way hierarchical clustering grouped the eight populations strictly according to species into two major clusters and organized the 20 traits into four functional modules representing floral，foliar，fruit and anther haracters.（4）Linear mixed-model analysis further revealed that temperature and precipitation significantly explained variation in several floral and fruit traits（marginal R² up to 0.474），although population genetic structure remained the dominant source of phenotypic differentiation. Overall，wild tree peonies display pronounced genetic variation at interspecific，inter-population and intra-population levels，with greater variation among populations than within populations，while environmental factors also contribute significantly to key traits. Therefore，as many wild peony populations as possible should be protected in their habitats. Suggested that more populations with less individuals in each population should be taken as samples when researchers collect germplasm for studies about off-site conservations and genetic improvements.

Key words: tree peony, phenotype, diversity, nature population, phenotypic differentiation coefficient, phenotypic diversity index