3.3 | Phylogenetic diversity and structure
The
TR and PD were higher at both ends of the ranges. The lowest TR and PD
values were observed in Minfeng
County, and the values in the
eastern area were higher than those in the western area (Table 2).
In the present study, only one SES-PD value was greater than 0, and all
other SES-PD values were less than 0. The maximum and minimum SES-PDs
were 3.56 and -5.69, respectively
(Table 2). The negative SES-PD
values indicated that 27 of the 28 county-level communities were young
flora, while the positive SES-PD value for the Banma County indicated
that the flora there were relatively ancient. No significant differences
were observed in the SES-PDs between Jiuzhi County and Shache County,
whereas significant differences were detected among the other SES-PD
values (P
< 0.05) (Table 2).
Phylogenetic
structure can be revealed by the NRI and NTI. These indexes indicated
that the
different
counties had different phylogenetic structures
(Figures 3, 4). Negative NRIs in
11 county-level communities indicated phylogenetic dispersion. These
counties were located mainly in the western and middle parts of the
Kunlun Mountains. Conversely, positive NRIs in the 17 other county-level
communities indicated phylogenetic clustering. These counties were
distributed mainly in the eastern and middle parts of the Kunlun
Mountains. Significant differences were detected between four negative
NRIs (P < 0.05) and three positive NRIs (P < 0.05),
while the NRIs of the remaining 21 counties were not significant (Figure
3). In addition, the NTIs of 27 county-level communities were positive,
of which 24 NTIs were statistically significant (P < 0.05).
Only the community in Banma County had a negative NTI that was also
significantly different (P < 0.05) (Figure 4). However,
inconsistent trends were observed between the NRIs and NTIs in 10
counties, most of which bordered the Qaidam and Tarim Basins (Figures 3,
4).
Overall, both the NRI and NTI values were
negative in the Banma County. The
other 27 counties had positive NTI values, 17 of which also had positive
NRI values. Ten counties had negative NRI values and were adjacent to
the Qaidam and Tarim Basins
(Figures 3, 4).