4 DISCUSS
The Satyrium plant species are important resources, but they are
endangered and rare (Mishra & Saklani, 2012). MaxEnt models were
applied to predict current and future potential distribution areas ofS. ciliatum , S. nepalense , and S. yunnanense.Generally, the evaluation index of prediction model accuracy is the ROC
curve, which has the following advantage: the AUC value is not affected
by the threshold and can be used for the comparison of various models
(Fielding et al., 1997). However, further research shows that it is
inaccurate to evaluate accuracy only by AUC value because it cannot
reflect wrong spatial distribution information, and calculate the
omission rate and error rate by a single method (Lobo et al., 2008;
Peterson et al., 2008). Nowadays, the information measurement index AUC
is used to select the ideal setting parameters of MaxEnt (Muscarella et
al., 2014); the method of combining omission rate and AUC value is used
to obtain the best parameters (Radosavljevic & Anderson., 2014); TSS
value is used to evaluate accuracy (Bedia et al., 2011); and multiple
parameters are set to select the optimal result (Elith et al., 2010;
Warren et al., 2011). TSS can accurately correct the overall accuracy of
the model without being affected by the size of the species validation
data set and without depending on the model threshold, therefore,
AUC and TSS values are used as
evaluation indexes in this prediction (Bedia et al., 2011).
According to the four different future scenarios, the suitable habitat
area for Satyrium in China will be extended in the 2050s and
2070s, moving slowly to higher altitude areas in the northwest side of
China, where the humidity and habitat are suitable for the growth of theSatyrium species. These scenarios are consistent with the results
of a study on the Houttuynia cordata Thunb (Ceercao) habitat
suitability. In the study, the suitable distribution area in the high
emission scenario was greater than that in the low emission scenario
(Liu et al., 2021). The increased precipitation in China in the SSP5 -
8.5 emission scenario was higher than in the low concentration emission
scenario (Yue et al., 2021). This shows the increased precipitation in
the high concentration emission scenario can solve the limitations of
precipitation on distribution of species, and the increased
precipitation in the low concentration emission scenario cannot reduce
or solve the limitations of precipitation on the distribution of
species. This may also be the reason the most suitable habitat area and
the increasing area of the Satyrium species are the largest in
the high concentration emission scenario, particularly the SSP5-8.5
scenario. The prediction shows that the upcoming future will be the most
suitable for the growth of the Satyrium species. It shows that,
generally, the suitable habitat is stable and the species will not face
extinction due to climate change. This study shows the new areas for
species distribution. The findings are in agreement with those of
previous studies, indicating that in some regions, habitat suitability
of plant species improves under climate change conditions (Feng et al.,
2020; Li et al., 2019). The distribution of species under future
climatic scenarios predicts that the area of species covering 20% of
the earth’s surface will face the risk of extinction, and about
15%–37% of the species will be endangered (Thomas et al., 2004). One
of the reasons for the endangered status of Satyrium is that mostSatyrium species are hermaphroditic. Some species rely on birds
and other animals for long-distance transmission, the species population
is small, and the quality of seed development is low because of
long-distance pollination (Johnson et al., 2011). This study’s results
provide a reliable basis for protecting Satyrium . People should
effectively protect its native habitat and population. Nature reserves
for Satyrium should be set up now according to the prediction
results, and they should be strengthened to minimize
human-made damage.
The results show that isothermality (bio3) and temperature seasonality
(bio4) are the common factors in the three species, indicating that the
main environmental variable affecting the appropriate distribution ofSatyrium is temperature. Zhao et. al. (2021) used the MaxEnt
model to predict the potential suitable habitat of Chinese fir in China.
Their results showed that temperature factors are more important than
precipitation factors influencing habitat suitability for Chinese fir.
Lou et al. (2015) used regression models to predict tea crop yield
responses to climate change, finding that temperature plays a
significant role in tea production and quality. Environmental variables
like temperature can estimate plant distribution patterns (Deblauwe et
al., 2016; Wang, R. et al., 2021).
In regard to S. nepalense , precipitation is one of the
environment variables influencing its geographic distribution.Satyrium is a perennial terrestrial orchid distributed in
Southwest China (Deng et al., 2019). Terrestrial orchids are typically
cold tolerant, live in low-temperature environments, and are highly
distributed in areas with large amounts of annual rainfall (Phillips et
al. 2011; Poff et al., 2016). More studies have shown that the dominant
variables restricting geographical distribution of plants are energy
supply, plenty of water, and cold tolerance (Zhou & Wang, 2000). Based
on the prediction of the MaxEnt model, the area of the current potential
suitable habitat of Satyrium is mainly located in Southwest
China, which has a typical subtropical monsoon climate (Luo et al.,
2021). Previous studies have indicated that precipitation is the main
variable affecting plant growth,
regeneration, nutrient cycles, and community productivity in different
habitats (Miranda et al., 2011). Climate change can determine
geographical distribution of species, and geographical distribution of
species can respond to changes in climate (Warren et al., 2021). Global
warming has changed the structures of terrestrial ecosystems, which have
changed the habitats and geographical distribution functions of species
in turn (Ghini et al., 2012). For instance, climate, topography, soil,
human disturbance, and spatial constraints are significant to the
distribution of many different spatial scales (Eiserhardt et al., 2011;
Parisien et al., 2009). The environmental data used in the study
included bioclimatic variables and topographic variables in WorldClim.
We did not study soil type, land use, human activities, biological
interaction, and other factors that influence the distribution ofSatyrium . The more factors that are included, the more accurate
the prediction will be. Therefore, other factors affecting the potential
suitable habitat of Satyrium should be studied in the future,
with different niche prediction models predicting areas of potential
suitable habitats. This will make the prediction of results more
reliable.