3.2 Population Grouping
Based on SAMOVA, we found that the F CT value was
the highest when K = 3, which resulted in separation of
populations into three groups. Among them, both the first group (P1-6)
and the second group (P7-12) contained six populations, and the third
group consisted of all other populations. However, three populations
(P6-8) were highly similar in their geographic distributions and their
habitats according to our field surveys, and this was why we did not
adopt K = 4. When K was > 4, at least one
group consisted of a single population (Table S3), indicating
over-splitting and loss of geographic structural data. Thus, we thought
it was the most reasonable to divide 43 populations of P. villosainto two major groups.
The first group, Group 1, identified using SAMOVA, consisted of 12
populations (P1-12), which mainly occurred in the central and eastern
regions of the Inner Mongolian Plateau, while the second one, Group 2,
was composed all other populations, which distributed throughout the
range of the species in China. Notably, the populations of Group 1 tend
to be found at lower elevations compared to those from Group 2 (Table S1
& Figure S1). Groupings of populations can facilitate detection of
finer scale geographic structures (i.e., within groups) juxtaposed with
broader, regional patterns (i.e., between groups) (Li et al., 2020).
Therefore, we used the recovered grouping scheme for downstream data
analysis in our present study.