Vascular plant nano-hotspots in the central Balkan Peninsula – A novel GIS-based approach for identifying centres of species richness

Although the Balkan Peninsula is one of the most biodiverse regions in Europe, there is still a lack of knowledge about its plant diversity. This study aimed to fill this knowledge gap by studying the spatial patterns of plant diversity on three massifs that had previously been identified as hotspots for endemics, Arctic-alpine and Boreal relics. To achieve this objective, we employed data gap and GIS analysis techniques to identify species-rich areas and to assess the relationship between taxa richness and the components of environmental heterogeneity. Targeted field surveys were carried out over two seasons, and a total of 97 environmental factors were selected as elements of environmental heterogeneity. A considerable number of hotspots of plant richness were identified, comprising 18 actual and 57 potential nano-hotspots. Most of the identified potential nano-hotspots are situated in areas characterized by a pronounced canyon or ravine formation, while the lowest number was observed at the highest elevations of the mountains, especially in regions where silicate substrates predominate. Our findings confirm the importance of factors previously identified as pivotal, including terrain ruggedness, topoclimate, elevation, geological substrate, and vegetation types, and for the first time suggest that hydrographic factors exert a strong influence on patterns of species richness. Given the considerable taxa richness observed in the ravine habitats of the study area, which makes them of high conservation value, it is essential to implement robust protective mechanisms to mitigate the impending effects of global warming and carefully plan the construction of hydropower plants. • Using the total number of vascular plants, data gap and GIS analysis, we identified drivers of species richness and nano-hotspots. • Specifically, we identified real and potential nano-hotspots in three pilot areas. • A positive correlation was observed between species richness and various topographic, climatic, hydrographic, vegetational and land cover factors. • Elevation and slope range, cover and edge density of running water and vegetation diversity demonstrated the greatest predictive potential. • The results of our study underscore the importance of adopting an integrated approach to studying fine-scale patterns of species richness.