<i>Parnassia kotzebuei</i> (Parnassiaceae) at the western limit of its distribution

During a floristic survey of the territory of the mountain site "Sokol" of the Ust-Lensky Reserve, new localities of Parnassia kotzebuei were found at the western limit of its range, in the lower reaches of the Lena River. Previously, the limit of this species range was believed to be in the lower reaches of the Indigirka River. Parnassia kotzebuei is included in the list of rare and specially protected plants of the Republic of Sakha (Yakutia), is listed in the regional Red Data Books, and its presence on the territory of the Ust-Lensky Reserve will serve as an additional factor in ensuring the preservation of its populations. Hypotheses of the species appearance in this territory and its distribution in the adjacent area are expressed. Two possible versions are assumed: the relict (Pleistocene) origin of the populations, and the introduction of seeds by waterfowl beards. In both cases, the probability of its hydrochoric dissemination in the vicinity is allowed.