Relationship between Morphology and Phylogeny in the Slow-Flashing Genji Firefly, Nipponoluciola cruciata, from Shizuoka Prefecture, Central Japan

The Genji firefly, Nipponoluciola cruciata, exhibits geographic variation in flash behavior, morphology, and phylogeny across Japan. Although populations in Shizuoka Prefecture belong to the western phylogenetic lineage, they display the slow-flash pattern characteristic of eastern populations. To examine the relationship between morphology and phylogeny in this unusual population, published morphological data were reanalyzed using principal component analysis (PCA). Male specimens from Gunma, Yamanashi, and Shizuoka Prefectures were compared based on external and genital morphological characters. The PCA of genital morphology clearly separated the Shizuoka and Gunma populations, whereas it indicated substantial similarity between the Shizuoka and phylogenetically related Yamanashi populations. In contrast, the PCA of external morphology suggested greater similarity between the Shizuoka and Gunma populations than between the Shizuoka and Yamanashi populations. These results suggest that the Shizuoka population exhibits different patterns of morphological affinity depending on the trait category. Together with its previously reported slow-flash pattern, these findings highlight the distinctiveness of the Shizuoka population and suggest that morphological variation in N. cruciata does not correspond uniformly with phylogenetic relationships.