**1. Introduction**

Climate change is an indisputable reality today, evidenced by glacial melting from mountain areas, greening of alpine tundra or arctic, upward shifting of alpine tree lines, and shrub encroachment into alpine grassland [1–3]. Many scientists believe that mountains act as early warning systems and can provide direct evidence to understand potential changes in the lowland environment [4,5]. Mountains around the world vary in terms of shape, extension, elevation, climate change impact, and biodiversity because of the differences in their geographic locations coupled with the complex region-specific hydrothermal condition [5,6]. Most studies have shown that the Qinghai-Tibet Plateau sensu lato (QTPsl)

**Citation:** Shi, N.; Wang, C.; Wang, J.; Wu, N.; Naudiyal, N.; Zhang, L.; Wang, L.; Sun, J.; Du, W.; Wei, Y.; et al. Biogeographic Patterns and Richness of the *Meconopsis* Species and Their Influence Factors across the Pan-Himalaya and Adjacent Regions. *Diversity* **2022**, *14*, 661. https:// doi.org/10.3390/d14080661

Academic Editor: Michel Baguette

Received: 22 June 2022 Accepted: 9 August 2022 Published: 16 August 2022

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

is not a natural tectonic association, but rather comprises a "plateau platform" (i.e., Qinghai-Tibet Plateau sensu stricto; QTPss) [7,8], the Himalaya, and the Hengduan Mountains [9,10]. Together these three regions are also referred to as the pan-Himalayan region [10,11] which boasts of complex topography, diverse geomorphological types, a wide altitudinal range, and different soil textures and geological conditions. This region, where one can observe diverse habitats within a short distance, supports a variety of endemic and endangered species [11,12]. The pan-Himalayan region is an important biodiversity hotspot with the world's highest diversity of alpine plants, attracting extensive scientific attentions [10,13,14].

Biodiversity, especially plant diversity, plays an important role in regulating climate, stabilizing the structure and functions of ecosystems, and providing ecosystem services for humans [15,16]. However, this diversity of plant resources has been constantly threatened by climate change and excessive anthropogenic disturbance since the last century [17,18]. As one of the most severe threats to global biodiversity, climate change has interfered with the composition, structure, and functioning of many mountainous ecosystems, resulting in an ecosystem imbalance that eventually affects human well-being [19–21]. Climate variables can determine the geographic distribution patterns of plant species [22] in addition to several non-climatic factors, such as topography, soil types, and land use, which equally impact species distribution [23]. The geographical distribution of alpine plants, in particular, is sensitive to the interaction between climate and topography [11,24]. Furthermore, human disturbances in mountainous landscapes not only accelerate climate change but also cause severe habitat loss and fragmentation and support the invasion of alien species, which are often directly or indirectly related to the loss of biodiversity [18,25–27]. Many native plant habitats have suffered habitat loss and fragmentation [23,25,27] that leads to the creation of isolated habitat patches resulting in an eventual decline in species viability across the landscape and ultimately reduction of species diversity across the ecosystem [18,28]. Numerous studies have shown the negative impact of fragmentation at the landscape scale on species diversity; however, the ecological effects of fragmentation at larger macroscopic scales are not clearly demonstrated [29,30]. Habitat loss and fragmentation are the primary drivers for the extinction of plant species [31]. Maintaining plant diversity while ensuring their sustainable utilization for human well-being is a common global concern [32]. Species richness is a fundamental scale for measuring regional diversity and the basis for constructing evolutionary and ecological models and conservation strategies [33]. Species diversity at the local scale is influenced by habitat heterogeneity such as geographic differences, climate, topography (elevation, slope, slope direction, etc.), and latitude and longitude, among other factors [34,35]. Thus, understanding the geographic distribution patterns of species richness in a particular area is of great scientific significance for the conservation, development, and sustainable utilization of plant resources.

The genus *Meconopsis* (Himalayan or blue poppies) belongs to the Papaveraceae family and contains over 70 species [36]. These plants are mainly localized in the Qinghai-Tibet Plateau, Hengduan Mountains, and Himalaya between the elevational range of 2000 m to 5800 m, where habitat changes from temperate forests to alpine meadows to screes and nival zones [37,38]. The East Himalaya-Hengduan Mountains region is the center of diversity for *Meconopsis* genus. *Meconopsis* plays a unique role in the alpine ecosystem. It is an important component of the regional biodiversity and participates in primary production, which is critical for ecosystem functioning [39]. *Meconopsis* is well-known for its colorful, attractive, and gracefully postured flower with high ornamental value and is widely used in horticultural gardening [40]. Species of this genus are symbols of tenacious vitalities since they bloom with beautiful flowers despite the extremely cold and harsh environment, inspiring those who live in the same extreme conditions [41]. These flowers are often shown in frescoes and thangkas, being closely related to Tibetan Buddhism, being the prototype of the ubala flower held by the *Green Tara* for relieving suffering [42]. *Meconopsis* is valued for its medicinal properties with a long clinical history in China and other Asian countries. The medicinal properties of the genus were first recorded in the Tibetan medicine book *Yue Wang Yao Zhen*. Famous masterpieces of traditional Tibetan herbal medicine such as

*The Four Medical Tantras* and *Jing Zhu Materia Medica* have described the use of *Meconopsis* for its anti-inflammatory or analgesic properties [41]. For instance, the flowers or whole plant of *M. integrifolia* can be used for curing hepatitis, pneumonia, liver heat, lung heat, and edema [41]. Recently, a variety of isoquinoline alkaloids with bioactivities have been isolated from *Meconopsis*, which partly explains its unique therapeutic effects [41]. However, only a few species of this genus have been cultivated for floriculture successfully in a controlled environment [41,43]. With the development of the pharmaceutical economy in these regions, overexploitation and anthropogenic habitat destruction are increasingly threatening the survival of many wild *Meconopsis* species, and some *Meconopsis* species have been placed under protection by law [41,42]. Hence, it is of great necessity to map the habitat distribution and ensure the sustainable development of *Meconopsis* from both natural and social perspectives for their habitat conservation and sustainable development.

Predicting the potential species distribution is a significant step toward habitat protection, and the species distribution model (SDM) has become one of the most widely used tools for simulating the potential distribution of organisms [44,45]. The basic principle of SDM is to correlate current species distribution with corresponding environmental variables to estimate the ecological requirements of a species based on ecological niches, thus predicting the suitable habitat [46,47]. The MaxEnt model is the most widely used among the many SDMs because it not only provides stable and reliable prediction results even with small sample data sizes but can work with presence-only data unlike some other models [42,48,49]. Due to the high prediction accuracy, it has been widely used in studies on the spatial distribution of species in response to climate change [9], suitable planting areas for important economic crops, and priority conservation areas for endangered and rare species [50–52]. The screening of suitable habitats and identifying priority conservation areas is critical for habitat management. However, to develop effective landscape management plans, the role of landscape fragmentation in determining the distribution and survival of species cannot be ignored.

Landscape fragmentation is the process by which the surface of a landscape is transformed from a regular homogeneous entity into smaller, complex, and poorly connected patches, mainly as a result of human activities and environmental disturbances [53]. The landscape index can reflect the landscape information well and is a common method to study landscape fragmentation quantitatively. Landscape indices are generally calculated using FragStats (Fragment Statistic), a software program for calculating indices of different types of landscape patterns in classified map patterns or patch mosaics, and analysis of spatial patterns for quantifying landscape structure (i.e., composition and configuration) [54]. It offers a comprehensive choice for the calculation of landscape pattern indices, and three levels (individual patch, patch class, and landscape) of the landscape index can be obtained after the calculation [54]. It is of practical significance to clarify the relationship between landscape pattern and species richness for the conservation and sustainable development of diversity.

In this study, we used MaxEnt to predict the potential distribution pattern of *Meconopsis* and used regression analysis to explore the geospatial pattern of species richness for *Meconopsis* in the pan-Himalaya and its adjacent regions. In addition, we divided the study area into five subregions and used landscape index as a variable to measure landscape fragmentation, and compared the species richness of *Meconopsis* in each subregion (Figure 1). This paper aimed to: (1) predict the potential distribution of *Meconopsis* and determine the key factors affecting the distribution of these species in the pan-Himalaya and adjacent regions; (2) clarify the species richness pattern of *Meconopsis* and analyze the distribution characteristics of species richness under different altitude, latitude and longitude, and other topographical factors (aspect and slope); and (3) assess the degree of landscape fragmentation and species richness *Meconopsis* in five subregions. The results will contribute to identifying the appropriate geographical space available for *Meconopsis* species and help in ensuring sustainable utilization and management of the genus.

**Figure 1.** The conceptual framework of the study.

### **2. Materials and Methods**
