Genetic differentiation
AMOVA pointed out a high genetic differentiation level amongCerasus serrulata populations (cpDNA:F st=0.69325, ITS:F st=0.78692), signifying the existence of a
phylogeographic structure (N ST=0.388
> G ST=0.328, P <
0.05). A similar high diversity level was also detected in C.
dielsiana (ITS: F ST=0.7827) (Zhu et al. ,
2019), but contrarily low levels were unraveled in C.
pseudocerasus landraces (ISSR: F ST=0.308 ) (Chen
et al., 2018), C. pseudocerasus containing both wild populations
and landraces (cpDNA: F ST=0.24922, ITS:F ST=0.31571) (Chen et al., 2015), C.
tomentosa (SSR: F ST=0.181) (He et al., 2015),C. lannesiana var. speciosa (cpDNA:F ST= 0.1655) (Kato et al. , 2011), C.
mahaleb (RSPD: F ST= 0.1646) (Jordano and Godoy,
2000), C. campanulata (SSR: F ST=0.1477)
(Lv, 2006; Su, 2007), C. jamasakura (SSR:F ST= 0.043) (Tsuda et al., 2009). This might
because both C. serrulata and C. dielsiana are much more
widely distributed than most of species in Cerasus . Additionally,
adequate seed flow were also believed to weaken the interspecific
divergence of C. pseudocerasus and other similar Cerasusspecies (Chen et al., 2015; Kato et al., 2011; Tsuda et al., 2009; Zhu
et al., 2019).
Together of the cladograms and networks of both cpDNA and ITS sequences,
finally two groups of C. serrulata within all the regions were
defined: one mainly consisted of the northwest groups (NW), and the
other was primarily composed of the left groups (SE+SW). Nevertheless,
the northeast group (NE), involving population FHS in Liaoning Province
and a foreign population K-NS in Korea, appeared a confusing
phylogeographic pattern. It was assigned to group SE+SW in cpDNA
analysis, but was related to group NW in ITS analysis. An earlier study
based on nuclear SSRs, involving the main northeast and southeast
populations of C. serrulata , indicated a consistent connection
within the eastern regions involving population FHS and K-NS (Yi et al.,
2018), which in accordance with the result of cpDNA analysis, making the
distribution more puzzled. N ST/G ST analysis manifested no or weak
phylogeographic structure within groups in northwest (NW)
(N ST=0.305 <G ST=0.461, P > 0.05) and
northeast (NE) (N ST=0.496 >G ST=0.473, P < 0.05). Actually,C. serrulata distributions were also recorded in Hebei Province
and Heilongjiang Province in China, as well as in Japan, but we failed
to obtain samples in these regions. Thus, the lack of the comprehensive
sampling in Northeast China and Japan was mainly ought to be the reason
of this confusion.