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We studied the distribution of two Pinguicula (Butterwort) species in Gunma Prefecture, Japan based on our herbarium specimen examinations and field observations. As a result, several localities of Pinguicula macroceras, such as Mt. Akagi-yama or the Tanigawa Mountain Range, were present today. In addition, two new localities of P. macroceras, Mts. Hotaka-yama and Ojikazawa-no-kashira, which had not been previously recorded, were found. However, only a single locality of P. ramosa, a threatened species (Endangered in the Red List of Gunma Prefecture and Vulnerable in the Red List of the Ministry of the Environment of Japan), was confirmed to be present in the prefecture. The two species have extremely narrow environmental preference and are restricted to specific environmental niches. The population size of both species at each microhabitat is small and there is a potential risk of disappearance of those localities in the future by the impacts of environmental stress or human activities. This study documents the current situations of the genus in Gunma Prefecture and suggests that urgent conservation is necessary to protect both the two species and their habitats in the prefecture.

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