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Fig. 1. Bayesian clustering results for Pterocarya fraxinifolia in the Hyrcanian region (N = 116) estimated along two altitudinal gradients from K = 3 and an associated map of the mean membership probabilities per site from STRUCTURE. Each individual is represented by a vertical bar partitioned into K segments, which represents the amount of ancestry of its genome corresponding to K clusters. Visualization was improved by sorting the genotypes by site. Gradient 1: Myarkola, Sad, and Miana; gradient 2: Chaybagh, Atoo, and Ladjim. (a) Output from STRUCTURE. (b) Output from BAPS. (c) Results of DAPC analysis in R.

Table 1. Geographical characteristics and sample size of investigated populations in two gradients along two river systems.
Population name Latitude (UTM) Longitude (UTM) Altitude (m a.s.l.) Sample size
Tajan river (gradient 1) Myarkola 672536.3 4051845.08 50–60 20
Sad 697694.9 4017597.8 350–400 20
Miana 703567.39 3996839.29 900–970 18
Talar river (gradient 2) Chaybagh 669888.3 4023492.3 200–250 20
Atoo 681346.47 4008915.14 400–450 18
Ladjim 686691.74 4013147.26 900–950 20
Table 2. Genetic variability within two gradients of Pterocarya fraxinifolia populations.
  Elevation Population Effective number of alleles (Ne) Observed
heterozygosity (Ho)
Expected
heterozygosity (He)
Allelic
richness (Ar)
Private allelic
richness (PAr)
Gradient 1 Low Myarkola 5.7 ± 0.73 0.78 ± 0.1 0.807 ± 0.028 4.06 0.99
Medium Sad 4.7 ± 0.36 0.85 ± 0.067 0.78 ± 0.02 3.8 0.4
High Miana 5.1 ± 0.44 0.86 ± 0.07 0.79 ± 0.02 3.9 0.38
Gradient 2 Low Chaybagh 3.72 ± 0.23 0.79 ± 0.11 0.726 ± 0.018 3.3 0.1
Medium Atoo 4.27 ± 0.51 0.87 ± 0.09 0.751 ± 0.025 3.5 0.2
High Ladjim 4.25 ± 0.69 0.86 ± 0.11 0.730 ± 0.043 3.4 0.14
Table 3. Analyses of molecular variance (AMOVA) for two gradients of Pterocarya fraxinifolia from Hyrcanian forest using SSR markers.
AMOVA component AMOVA genetic distance option
S.O.V d.f SS MS Est. Var. % of Variance PhiPT Rst Fst Nm
Gradient 1 Among Pops 2 27.76 13.8 0.45 9% 0.086** 0.049** 0.046** 5.13
Within Pops 55 284.95 5.18 5.18 91%
Total 57 312.72 5.63 100%
Gradient 2 Among Pops 2 22.13 11.06 0.34 7 0.075** 0.052** 0.036** 6.6
Within Pops 55 237.68 4.32 4.32 93
Total 57 259.82 4.67 100
Total Among Pops 5 85.1 17 0.63 12 0.11** 0.037** 0.062** 3.77
Within 110 521.3 4.7 88
Total 115 606.4 4.7 5.37 100
Statistics include sums of squared deviations (SS); mean squared deviations (MS), variance component estimates (Est. Var.).
** – p-value < 0.01.
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Fig. 2. The result of DAPC analysis with populations used as clusters: 1 – Myarkola, 2 – Sad, 3 – Miana, 4 – Chaybagh, 5 – Atoo, 6 – Ladjim. Green colours indicated populations from gradient 1, blue and purple – populations from gradient 2.

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Fig. 3. Result of the population assignment. (a) Pairwise population assignment graphs of gradient 1 vs. gradient 2. (b) Assignment of the populations of gradient 1. (c) Assignment of the populations of gradient 2.

Table 4. Summary of population assignment outcomes to “self” or “other” population.
  Pop Gradient 1 Pops Gradient 2 Pops Total Percent
All populations* Self Pop 52 57 109 94%
Other Pop 6 1 7 6%
Pop Myarkola Sad Miana Total Percent
Gradient 1 Self Pop 17 20 18 55 95%
Other Pop 3 0 0 3 5%
Pop Chaybagh Atoo Ladjim Total Percent
Gradient 2 Self Pop 18 16 16 50 86%
Other Pop 2 2 4 8 14%
* – All population in each gradient grouped as one population.
Table 5. Pairwise population gene flow (Nm) values (below diagonal) and pairwise population genetic distance based on Fst values (above diagonal).
Populations Myarkola Sad Miana
Gradient 1 Myarkola 0.000 0.058 0.025
Sad 9.88 0.000 4.343
Miana 4.343 0.054 0.000
Populations Chaybagh Atoo Ladjim
Gradient 2 Chaybagh 0.000 0.041 0.026
Atoo 5.856 0.000 0.043
Ladjim 9.310 5.564 0.000
Nm – the product of the effective population number and rate of migration among populations.
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Fig. 4. Migration pattern of Pterocarya fraxinifolia within and among the river populations.