Hyosig Won1P and Jin Hee Park2

1Department of Biological Science, Daegu University, Gyungsan, Gyungbuk, South Korea; 2Nakdonggang National Institute of Biological Resources, Sangju, South Korea

Viola arcuata Blume is a widely distributed violate species ranging from Indonesia to Russia (Far East). Plastid genomes have previously been reported for samples as V. arcuata from Korea and as V. verecunda A. Gray from Japan, with the latter often been treated as conspecific. Here, we reportthe complete plastid genome sequence of V. arcuata from a population collected from Northern Laos to investigate geographic patterns of variation in this broadly distributed taxon. The Laotian plastid genome is 157,768 bp in length (GC content 36.3%) and exhibits the typical quadripartite sturcutre of angiosperm plastomes, consisting of a large single-copy (LSC) region of 86,356 bp, a small single-copy (SSC) region of 17,294 bp, and a pair of inverted repeats (IR) each 27,059 bp long. It encodes 112 unique genes: 78 protein-coding genes, 4 ribosomal RNA genes, and 30 transfer RNA genes. Pairwise sequence comparisons revealed 0.765% divergence (1,208 bp differences) between the Laotian and Korean samples, and 0.761% (1,201 bp) between the Laotian and Japanese samples. In contrast, the Korean and Japanese samples differed by only 0.036% (57 bp). This pattern – low divergence between the closely situated Korean and Japanese populations, but substantially higher divergence to the distant Laotian population – is consistent with an isolation-by-distance (IBD) scenario, where genetic differentiation increases with geographic separation. These results provide the first plastid genome data for V. arcuata from mainland Southeast Asia and highlight the potential role of geographic distance in shaping plastome variation within this species complex. Further sampling across the range, combined with nuclear markers, will help clarify whether this reflects neutral IBD or contributions from cryptic divergence or historical barriers.