FIGURE LEGENDS
FIGURE 1 Map of southeastern China, showing the sampling
locations of C. chuniana populations used in this study. The
mountain ranges involved in the study are shown in orange shadows.
Populations sampled in the Nanling Mts. are indicated with black
circles; populations in the east are indicated with triangles.
Vicariance events detected in S-DIVA are shown with blue lines. The key
at bottom right indicates elevational ranges. Additional accession
information is given in Table 1.
FIGURE 2 Potentially suitable areas for C. chunianapredicted by ecological niche modeling (ENM) and corresponding variation
in temperature. Four different periods were applied, i.e., the Last
Interglacial (LIG), the Last Glacial Maximum (LGM), the Middle Holocene
(MH), and current. Suitable and unsuitable habitats are indicated in red
and grey, respectively, where red represents the habitat suitability
(occurrence probability) higher than 44.93%. The temperature variations
in each period are indicated in the gray boxes. (a) LIG; arrows point to
relevant mountain ranges. The temperature during secondary contact
(TSEC ) is indicated. (b) Potentially suitable
areas projected in comparison with a layer of GIS-based vegetation map
at LGM. Numbers 1‒8 represent different vegetation types at the LGM: 1,
tropical thorn scrub and scrub woodland; 2, open boreal woodland; 3,
semi-arid temperate woodland or scrub; 4, steppe-tundra; 5, polar and
alpine desert; 6, temperate desert; 7, forest steppe; and 8, dry steppe.
(c) The simulated distribution range at MH. (d) The current potential
distribution range, with black dots representing localities based on
herbarium specimen data and samples collected for the present study. The
most influential factors are listed in Table S1.
FIGURE 3 Phylogenetic tree of C. chuniana populations
based on maximum-likelihood (ML) method. Bootstrap percentages
(> 50) in the ML tree are indicated above the branches.Cercis chingii was used as the outgroup.
FIGURE 4 Chronogram of the Bayesian tree for divergence time
estimates, population structural clustering and ancestral area
reconstruction. Branch lengths were transformed via Markov chain Monte
Carlo (MCMC) simulations in the Bayesian time estimation. The light blue
bars indicate 95% confidence intervals. Individuals assigned to
different clusters in FastStructure are shown in corresponding colours
with K = 2, 3 and 7, with 7 as the optimal value. In the S-DIVA
analysis, colour legends indicate different geographical regions and
ancestral areas. Vicariance events (V1–V6) with high probabilities (P ≥
0.70), are shown for nodes. Populations in the Nanling Mts. are
distinguished within the dotted line frame. Time scale bar is shown at
the bottom. Various glacial and interglacial periods are indicated by
the braces, the former of which is below the bar while the latter above
the bar.
FIGURE 5 Schematic representation of the best fit demographic
models investigated in our study. Model names and the parameters
correspond to those in Tables S2 and S3, respectively. The left vertical
line shows time (Ma). Time of divergence (TDIV )
and secondary contact (TSEC ) are indicated as
dashed lines, with the corresponding glacial or interglacial periods
shown on the right. The top grey box represents the ancestral
populations with effective population size. The current population sizes
are shown at the bottom after the split between the Nanling Mts. (NL)
and the eastern mountains (ES). The migration directions and
corresponding rates (MES ) in individual migrants
per generation are shown between NL and ES.