Phylogenetic analysis of Rhododendron keiskei complex

Unraveling species boundaries is pivotal for evolutionary biology and conservation endeavors. However, it proves challenging in instances where recent speciation is intertwined with complex demographic histories and natural selection processes. The Rhododendron keiskei complex, an evergreen azalea distributed in East Asia, consists of a widespread variety (var. keiskei) and a more restricted var. hypoglaucum. Intriguingly, the latter is exceptionally rare yet displays a disjunction that spans approximately 1,100 km between Kanto region of Japan and one remote island off the Korean Peninsula. This study aimed to elucidate the evolutionary backgrounds of the enigmatic disjunctions of var. hypoglaucum and to propose species delimitation within this complex. This study employed an integrative approach, combining genomic data (MIG-seq-derived SNPs) with SEM analysis of leaf microstructures.