A New Record of the Critically Endangered Pondweed, Potamogeton lucens (Potamogetonaceae) from Aomori Prefecture, Japan

摘要

A new locality for Potamogeton lucens L. (Potamogetonaceae) was recorded from a pond in Aomori Pref., Tohoku District, Japan. In Japan, this species is critically endangered, and the sole remaining naturally established population was previously known only from one other locality. In June 2017, we found fragments of a submerged plant species that resembled P. lucens. We conducted field surveys and identified it as P. lucens based on morphological measurements, nuclear and chloroplast molecular analyses, a herbarium specimen survey, and pollen fertility. Although we could not reveal its population size and distribution in the pond, at least an established population exists because many fragments and a plant with developed roots were collected. This new locality of P. lucens represents the new northern limit of the species in Japan, which is over 500 kin away from its nearest distributional record. As developments are now in progress around the pond area, urgent protection by a conservation program is needed.