Plant phylogeography of the Balkan Peninsula: spatiotemporal patterns and processes

Abstract

The Balkan Peninsula is widely acknowledged as one of the centers of European biodiversity and a major glacial refugium for plant species. Its extensive geographic heterogeneity and diverse mosaic of habitats, coupled with relatively high environmental stability over long periods, have enabled the diversification of lineages and simultaneously fostered the long-term survival of diverse species. The increasing number of phylogeographically studied plant species in the region has substantially contributed to a better understanding of the relationships among closely related taxa and provided significant insights into intraspecific lineage differentiation. The present paper reviews the current knowledge on plant phylogeography in the Balkan Peninsula. By providing an updated overview of the most recent studies dealing with the diversity and evolution of Balkan plants, we explore the phylogeographic patterns and roles of refugia in structuring genetic diversity and highlight the crucial evolutionary processes that shaped the diversity of plants in the region. Molecular clock-based estimations highlight the importance of Pleistocene climatic fluctuations across taxonomic groups and lineage distribution patterns corroborate the persistence of multiple glacial refugia. Spatial congruence in phylogeographic splits is determined and discussed. An examination of phylogeographic connections with adjacent regions (i.e., the Alps, Apennine Peninsula, Asia Minor, Carpathians, and central Europe) uncovers several consistent patterns. Additionally, allopatric and ecological speciation, polyploidy, and hybridization are identified as crucial evolutionary mechanisms acting in the Balkan Peninsula and shaping species diversity. Furthermore, the existing research gaps are identified and future approaches with the potential to better understand the unique Balkan flora are highlighted.