Patterns of Functional Diversity, Species Diversity, and Endemicity Driven by Elevation and Topographic Complexity in a Mediterranean Mountain Refuge

This study investigates the variation in functional diversity (FD), species diversity (SD), and endemicity across all Mediterranean-type vegetation belts (MVB) within a topographically complex mountainous refuge, focusing on their relationships with topographic and climatic factors. Microclimatic processes and mosaic habitats caused by topographic complexity increase the plant diversity of the area. This diversity is reflected in our study through the representation of different habitat types. The relationship of functional and species diversity with environmental parameters was also modeled and mapped within this study conducted with approximately 5550 records of 1017 plant taxa from 136 study plots. Functional diversity was measured using Rao's quadratic entropy, and alpha species diversity values were calculated using the Shannon-Wiener index. Various regression models were trained and evaluated, and were assessed based on several statistical metrics. The final model selection, the Generalized Additive Model (GAM), was chosen based on its superior performance, ensuring the model not only fits the data well but also accurately predicts new data, thus optimizing both the validity and practical utility of the model. Our GAM results indicated that elevation is the most influential factor on diversity values, and that functional and species diversity curves show different trends with increasing elevation. Additionally, the topographic position index was identified as the most significant process affecting functional diversity in terms of "habitat filtering". In this context, the variation in functional diversity, species diversity, and endemism in mosaic habitats creates a mosaic of diversity. The results emphasize the importance of topographic complexity in maintaining biodiversity and highlight the need for targeted conservation strategies that prioritize areas with high functional diversity, such as the Meso-, Thermo-, and Supra- Mediterranean vegetation belts, alongside habitats with high endemicity, particularly in the Oro- and Cryoro- vegetation belts.