Integrative Assessment of Evidence for Anagenetic Speciation in Ulleungdo Endemic Plants: Plastid, Nuclear, and Morphological Perspectives

Abstract

Ulleungdo Island harbors several endemic plant lineages commonly interpreted as products of anagenetic speciation following long-distance colonization. Yet plastome phylogenies represent a single organellar genealogy and may conflict with nuclear genomic structure, morphology, or taxonomic boundaries. This critical mini-review evaluates whether plastid-based hypotheses for the origin and diversification of Ulleungdo endemics are supported by independent molecular and phenotypic evidence. We synthesize findings from comparative plastomics, chloroplast haplotype and network analyses, nuclear microsatellites, nrDNA sequencing, genome-wide multiplexed inter-simple sequence repeat genotyping by sequencing (MIG-seq) single-nucleotide polymorphisms (SNP), cytogenetics, morphology, and multicompartment phylogenomics. The evidence reveals heterogeneous evolutionary outcomes. Prunus takesimensis and Phedimus takesimensis are broadly consistent with probable single-origin scenarios, although confidence is constrained by progenitor sampling and marker resolution. Rubus takesimensis exhibits chloroplast non-monophyly and elevated haplotype diversity consistent with multiple maternal origins, whereas Acer takesimense shows signatures of historical drift and loss of rare nuclear alleles. Morphological, chromosomal, plastid, and nuclear–ribosomal evidence strongly support Allium ulleungense, while the delimitation of Viola ulleungdoensis remains unresolved. Plastid–nuclear incongruence in Hepatica maxima and Fagus multinervis further indicates that introgression, hybridization, incomplete lineage sorting, and restricted taxon sampling can complicate evolutionary inference. This comparative framework distinguishes species histories from provisional interpretations based on limited accessions or uniparentally inherited markers. The novelty of this review lies in its cross-taxon assessment of plastome–nuclear–morphological congruence rather than a descriptive plastome inventory. Ulleungdo lineages interpreted as products of anagenetic speciation do not exhibit a uniform genomic signature and that robust taxonomic, evolutionary, and conservation inference requires population-level integration of independently inherited genomic compartments with standardized morphological and reproductive data.