Zeta diversity has been proposed as a metric that complements α and β diversity by quantifying the number of species shared among multiple sites, thereby distinguishing contributions of rare and common species. Few studies, however, have combined zeta diversity with spatial autocorrelation analyses to evaluate vegetation fragmentation. This study applies zeta diversity with Moran’s I and hotspot analysis to examine the spatial structure of plant diversity in southern Korea, focusing on the impacts of land-use change and fragmentation. Zeta diversity decline revealed that rare species predominantly drove turnover at small spatial scales, whereas common species increasingly shaped compositional stability at larger scales. Moran’s I supported this scale-dependent transition: positive spatial autocorrelation was evident at low orders, but values decreased sharply with increasing order, approaching randomness at high orders. This indicates a shift from localized clustering by rare species to homogenized assemblages dominated by common species. Elevation consistently emerged as an important driver, while anthropogenic land use, including urban and agricultural areas, became more influential at larger scales. Hotspot analysis further showed that high-elevation areas functioned as stable cores of common species, while low-elevation areas, subject to intensive land use, emerged as coldspots where even common species failed to persist. Integrating zeta diversity with Moran’s I provides new insights into the scale dependence of biodiversity patterns and the spatial consequences of fragmentation. These findings highlight high-elevation zones as conservation cores and identify lowland coldspots as restoration priorities, providing scientific evidence for national biodiversity strategies.

The use of biota to analyze the spatial range and distribution of biogeographic regions is essential to gain a better understanding of the ecological processes that cause biotic differentiation and biodiversity at multiple spatiotemporal scales. Recently, the collection of high-resolution biological distribution data (e.g., specimens) and advances in analytical theory have led to their quantitative analysis and more refined spatial delineation. This study was conducted to redefine floristic zones in the southern part of the Korean Peninsula and to better understand the eco-evolutionary significance of the spatial distribution patterns. Based on the distribution data of 309,333 vascular plant species in the Korean Peninsula, we derived floristic zones using self-organizing maps. We compared the characteristics of the derived regions with those of historical floristic zones and ecologically important environmental factors (climate, geology, and geography). In a clustering analysis of the floristic assemblages, four distinct regions were identified, namely, the cold floristic zone (Zone I) in high-altitude regions at the center of the Korean Peninsula, cool floristic zone (Zone II) in high-altitude regions in the south of the Korean Peninsula, warm floristic zone (Zone III) in low-altitude regions in the central and southern parts of the Korean Peninsula, and maritime warm floristic zone (Zone IV) including the volcanic islands of Jejudo and Ulleungdo. A total of 1,099 taxa were common to the four floristic zones. Zone IV had the highest abundance of specific plants (those found in only one zone), with 404 taxa. This study improves floristic zone definitions using high-resolution regional biological distribution data. It will help better understand and re-establish regional species diversity. In addition, our study provides key data for hotspot analysis techniques required for the conservation of plant diversity.