1 These authors contributed equally to this work
Abstract: Satyrium is an endangered and rare genus of plant that has various pharmacodynamic functions. In this study, MaxEnt default parameters were adjusted by the ENMeval package. Optimized MaxEnt models were used in analyzing potential geographical distributions under current and future climatic conditions (the 2050s and 2070s) and dominant environmental variables influencing their geographic distribution. The results provided reference for implementation of long-term conservation and management approaches for the species. The results showed the area of the total suitable habitat for Satyrium ciliatum (S. ciliatum ) in China is 32.51 × 104km2, the total suitable habitat area forSatyrium nepalense (S. nepalense ) in China is 61.76 × 104 km2, and the area of the total suitable habitat forSatyrium yunnanense(S. yunnanense ) in China is 89.73 × 104km2 under current climatic conditions. The potential suitable habitat of Satyrium is mainly distributed in Southwest China. The major environmental variables influencing the geographical distribution of S. ciliatum were isothermality (bio3), temperature seasonality (bio4), and mean temperature of coldest quarter (bio11). Environmental variables such as isothermality (bio3), temperature seasonality (bio4), and precipitation of coldest quarter (bio19) affected the geographical distribution of S. nepalense ; and environmental variables such as isothermality (bio3), temperature seasonality (bio4), and lower temperature of coldest month (bio6) affected the geographical distribution of S. yunnanense . The distribution range ofSatyrium was extended as global warming increased, showing emissions of greenhouse gases with lower concentration (SSP1-2.6) and higher concentration (SSP5-8.5). According to the study, the distribution of suitable habitat will shift with a change to higher elevation areas and higher latitude areas in the future.
Keywords: Satyrium , MaxEnt, potential suitable habitat, environmental variables.
INTRODUCTION
Global warming is one of the crucial environmental problems facing the world today (Bayer et al., 2021). The global temperature has risen by about 1℃ in the past century, especially in the past 30 years, causing some plant species to move to higher elevation and higher latitude areas, as the Fifth Assessment Report (AR5) of the United Nations Intergovernmental Panel on Climate Change reported (Allen et al., 2014). Climate change in the future will affect the distribution range of species, resulting in a loss of biodiversity and the extinction of endangered species (Bellard et al., 2012). After climate change, the prediction of suitable habitats of species will be considered important in the future (Kumar et al., 2021).
In research on the geographical distribution range of plants affected by climate change, the species distribution model (SDM) uses distribution data of species and environmental variables in species habitats to predict the basic niche of species (Elith & Leathwick, 2009). These data are combined with environmental data in different periods for simulating the potential distribution areas of species in those periods (Araújo & Peterson, 2012). Among the many algorithms used in modeling species distribution, the maximum entropy approach (MaxEnt) has demonstrated fast modeling, wide use, high accuracy, and stability even with small sample sizes (Merow et al., 2013; Pearson et al., 2007). It can better anticipate the possible distribution of species compared with other SDMs (Phillips et al., 2006). If the MaxEnt model and ArcGis predict potential species distributions and biodiversity risks, relative strategies can be established to reduce climate change’s negative influence on global biodiversity.
S atyrium (Orchidaceae) is a rare and endangered plant genus with about 92 species—mostly found in Africa, with five species found in Madagascar alone, and four species found in Asian countries (Mahendran & Bai, 2009). Only three species have been found in China alone (all of which are endemic in China) (Cun, 2005). They are mostly distributed throughout Southwest China. Satyrium is also used for traditional herbal medicinal purposes; for example, Greek medics used Satyrium  tubers as aphrodisiacs (Teoh, 2016). Traditional health-care centers in India use the tubers of S atyrium nepalense (S. nepalense ) to make energy tonics and cure different types of fevers (Mishra et al., 2018). The number of Satyrium resources has been rapidly diminishing. Its population has a fragmented distribution, and it is in a rare and endangered status because of the value of herbal medicine and the serious deterioration of the ecological environment in recent times (Mahendran & Bai, 2009). Changes in climate will result in changes in the biological phenology period. This in turn will result in changes in the geographical distribution of species and an acceleration in the rate of species extinction. Therefore, it is necessary to adequately understand the changing trends of the geographical distribution of species under climate change conditions and to develop relative protection strategies.
Geographical distributions of three species from Satyrium genus were predicted by employing the MaxEnt model: (1) In current climatic conditions, the geographical distributions of Satyrium species in China and the relationships between these distributions and environmental variables were studied. (2) The main environmental variables limiting their potential geographical distribution were outlined. (3) The potential geographical distribution and shifting trends of the centroid of suitable habitats in China were predicted in future climate change scenarios. This study could offer a scientific foundation for the suitable protection and use of Satyrium .