3.3 Phylogenetic relationships and divergence times
The phylogenetic analysis yielded monophyly for each population with
mostly high bootstrap values (Figure 3). WYS1 was revealed to be
positioned at the first-diverging branch, followed by the populations
WYS2, LXS2 and LXS1. The populations in the Nanling Mts. formed a
monophyletic group, with NLE2 and NLE1 in the eastern Nanling Mts.
forming a clade separate from the others in the western Nanling Mts. The
time of origin of C. chuniana was estimated as 2.36 (95% HPD =
1.97–2.74) Ma during the early Pleistocene (Figure 4). WYS1 was first
divergent from the remaining populations, followed by WYS2/LXS2
diverging from the rest ca. 0.85 Ma during the Poyang Glacial period.
The divergence occurring between WYS2 and LXS2 was estimated as ca. 0.72
Ma, whereas the divergence between LSX1 and the populations in the
Nanling Mts. ca. 0.68 Ma. Both divergence times arose within the third
glacial period in China in Middle Pleistocene, although the exact
glacial and interglacial time ranges are still under debate (Figure 4).
Within the Nanling Mts., the eastern NLE1/NLE2 populations diverged from
the western NLW1‒NLW5 populations ca. 0.58 Ma, while NLW1 from the rest
western populations ca. 0.51 Ma, both of which were estimated as
occurring in the Dagu Glacial period (Figure 4). Population
diversifications in Nanling Mts. range from 0.20 to 0.29 Ma in the
western populations and from 0.35 to 0.37 Ma in the eastern ones,
respectively, the former of which is during the Lushan Glacial period
and the latter in the Dagu-Lushan Interglacial period. Population
diversifications in the east (WYS1-2 and LXS1-2) were calculated from
0.34 to 0.51 Ma, estimated spanning both the Dagu-Lushan Glacial and the
Interglacial periods (Figure 4).