This preprint synthesizes historical taxonomy, recent molecular findings, and original field observations on the genus Taraxacum in Japan. Drawing from early work by Tomitarō Makino and integrating modern phylogenetic and cytogenetic studies, it documents both endemic diversity and the rapid expansion of neophytic T. officinale in disturbed habitats. Field surveys in subalpine and montane regions (Naeba–Mikuni) in May–June 2025 compare the phenology and habitat preferences of T. officinale, T. japonicum, T. albidum, and related taxa. The study highlights ecological niche differentiation, the role of apomixis in reproductive success, and the conservation risks to sexual native taxa from hybridization and competitive displacement. Special attention is given to T. officinale as a case study in neophytism, demonstrating how subtle reproductive and phenological advantages enable dominance in anthropogenically altered environments. This version is a preliminary release and has not undergone peer review. Feedback and collaborative input from experts in taxonomy, plant ecology, and conservation biology are welcome. DOI: 10.5281/zenodo.16744596