Modeling the distribution of the plant species Zhumeria majdae under the influence of climatic and environmental factors in Hormozgan Province

Introduction

One of the major factors influencing the distribution and spread of plant species and the alteration of plant habitats—considered among the most critical global challenges of the 21st century—is climate change and global warming. Climate change has a direct impact on the distribution and survival of plant species. Numerous studies have shown that temperature fluctuations, changes in precipitation patterns, and recurring droughts have led to habitat shifts and even the extinction of certain plant species. Accordingly, both current and historical climatic conditions jointly determine today’s patterns of biodiversity and ecosystem functioning. However, climate change has significantly affected plant biodiversity and altered the geographical distribution of plant species, causing the extinction of some and placing many others at risk. These impacts have triggered substantial changes in ecosystems. Zhumeria majdae is an ecologically and economically valuable, endemic medicinal plant species in Iran, which is confined to certain mountainous regions of Hormozgan Province and has a limited distribution. Owing to its broad traditional medicinal uses—including treatment of digestive disorders, headache relief, and wound healing—it is exported to Persian Gulf countries and holds high ecological and commercial importance. Given its restricted range, high climatic sensitivity, and limited tolerance to environmental fluctuations, identifying the key environmental factors influencing its habitat and modeling its potential distribution are essential for its long-term conservation. The main objective of this study is to model the potential distribution of Zhumeria majdae in Hormozgan Province based on climatic and environmental variables, and to identify the most important factors determining its suitable habitat using the MaxEnt model.

Methodology

In this study, occurrence data of the Morkhosh species were initially extracted from various sources, including the Flora of Iran, Flora Iranica, the GBIF database, the Herbarium of the Research Institute of Forests and Rangelands, and other reputable scientific references. The occurrence points of this species were evaluated after validating their spatial accuracy using ArcGIS and Google Earth software. To extract climatic information, long-term records of temperature, precipitation, and relative humidity were collected from the synoptic and pluviometric stations of Fin, Sarchahan, and Tashkuiyeh. For analyzing the species distribution, 19 bioclimatic variables were used, including parameters such as mean annual temperature, annual precipitation, seasonal precipitation, minimum temperature of the coldest months, maximum temperature of the warmest months, and other BIOCLIM indices. These variables were obtained from the WorldClim global database with a spatial resolution of one kilometer. To examine multicollinearity among the variables, Pearson’s correlation test was performed using SPSS software, and highly correlated variables were removed. Species distribution modeling was carried out using MaxEnt software based solely on presence-only data. To evaluate the model’s performance, the jackknife test was used to determine the relative importance of the variables, and the Area Under the Curve (AUC) metric was used to assess the model’s predictive accuracy.

Results and discussion

The results of the MaxEnt model revealed that Zhumeria majdae distribution is most strongly influenced by winter precipitation (BIO19), accounting for 66.5% of the model’s predictive power. Other influential variables included slope (12.7%), precipitation of the wettest month (BIO13), and annual temperature range (BIO7). The species showed the highest probability of occurrence in regions with winter rainfall between 100 and 180 mm and winter temperatures ranging from 8 to 12°C. The response curves confirmed a steep increase in habitat suitability within these climatic ranges, with further increases in precipitation or temperature not significantly enhancing the species' presence. Comparative analysis across three primary habitats Mount Geno, Sarchahan, and Tang-e Zagh showed distinct phenological adaptations. In Mount Geno, due to higher rainfall and milder temperatures, the growing season was shorter (approximately 100 days), beginning in mid-February and ending with seed dispersal in late May. In contrast, Sarchahan and Tang-e Zagh exhibited longer growth periods (~120 days), with leaf emergence in late February and seed release by mid-June, reflecting adaptation to drier, warmer conditions. The species showed a clear preference for slopes between 10 and 35 degrees, where well-drained, rocky soils reduce interspecies competition. Suitability declined in flatter areas due to poor drainage and increased competition. These findings were corroborated by Jackknife tests, highlighting the ecological importance of both precipitation and topography. The model's high performance was confirmed by AUC values of 0.93 for training and 0.90 for testing datasets, indicating excellent predictive accuracy. The MaxEnt output map further identified areas in central and northern Hormozgan such as parts of Mount Geno, Hajjiabad, and Bandar Abbas highlands as highly suitable habitats under current climate conditions.

Conclusion

Despite its medicinal properties and high economic value, the Morkhosh species is vulnerable to future climate change due to its limited distribution and high sensitivity to climatic conditions. The results of this study showed that climatic factors, especially winter rainfall, play a decisive role in the species’ distribution, and any changes in rainfall patterns could threaten its natural survival. Variations in the length of the growing season across different regions also indicate the plant’s relative adaptation to variable environmental conditions; however, this adaptation is feasible only within a specific range of temperature and rainfall. Therefore, planning for the conservation of this species, identifying new suitable habitats, and developing targeted cultivation in areas with similar climatic conditions are of great importance. These results can also serve as a model for habitat analysis of other endemic and climate-sensitive species in Iran’s arid regions.