Evaluation of fruit and leaf morphological variability in bearberry (Arctostaphylos uva-ursi (L.) Spreng.) Dinaric Alps populations

The Dinaric Alps, including the Velebit Mountain in Croatia, are recognized for their rich plant biodiversity, including Arctic-alpine species like bearberry (Arctostaphylos uva-ursi (L.) Spreng., Ericaceae). This study investigates the morphological diversity of bearberry populations in the northern Dinaric Alps, focusing on fruit and leaf traits across three populations. Morphometric analysis of fruits and leaves revealed moderate variability, with leaves exhibiting higher variability than fruits. Significant correlations were found among both leaf and fruit traits, as well as between them, suggesting a linked growth pattern. Furthermore, contrary to our expectations of significant population differentiation due to the rugged montane terrain and the origin of the studied populations from different altitudes, 100% of the variability was attributed to within-population differences. This likely results from effective gene flow between populations, facilitated by wildlife species and traditional pastoral practices on the Velebit Mountain. Additionally, the lack of inter-population variability can be attributed to recolonization processes after the last glaciation, which suggest a shared regional origin of the studied populations. Although the studied populations originate from different altitudes, we did not detect a phenotypic plasticity with respect to this gradient. The lack of plasticity in the studied bearberry populations could be due to several reasons: the inherent stability of structural characteristics in response to environmental changes; similar soil and habitat conditions across the studied populations; and the reduced plasticity observed in alpine plants from higher altitudes due to extreme and stable environmental conditions. Overall, our study highlights the importance of preserving traditional land-use practices and enforcing legal protections within national and nature parks to conserve diversity and ensure the survival of bearberry populations. It underscores the role of human activities in enhancing plant population connectivity in alpine environments and calls for integrated conservation strategies that blend habitat protection with sustainable land use.