Many submerged plants in Japan are endangered, and thus detailed information on their distributions and habitats is necessary for conservation. However, the distribution survey is often difficult because they grow under water and flowers or seeds are often required for identification.
The objective of study was to reveal the distribution of Najas species (N. marina, N. tenuicaulis, N. minor, N. oguraensis, N. gracillima, N. yezoensis, N. graminea, N. ancistocarpa, N. orientalis) and environmental factors that influence the distribution. In this study, we applied eDNA method for investigation of Najas distributions. We conducted field pond surveys on 158 sites in Hyogo, Kagawa and Osaka Prefecture. In total, we found the distribution of Najas species in 16 sites including eDNA detection in 14 sites and target’s fragments collection in five sites. In detail, N. marina or N. tenuicaulis were detected in two sites, N. minor or N. oguraensis in 12 sites, N. gracillima or N. yezoensis in one site and N. graminea in one site. We then analyzed relationships between distribution of Najas and environmental factors, i.e., water qualities and landscape factors.