Ecological Risk Screening Summary - Najas tenuissima (a plant, no common name) - Uncertain Risk

Species that are considered uncertain risk need a more in-depth assessment beyond the Risk Summary to better define the species’ risk to U.S. environments.

Najas tenuissima is a rare monoecious annual aquatic plant found in the littoral zones of lakes and other disjunctive waterbodies in Eastern Europe, across Russia, and in Japan. N. tenuissima has narrow habitat requirements, tectonical and aqueoglacial lakes with clear water and sandy or muddy bottoms. Given this species’ apparent rarity and distribution across a broad geographic scale, its native range is not well understood. There are no records of introduction of N. tenuissima. Recent additional observations are considered to be part of the native range of the species. The history of invasiveness is no known nonnative population. The overall climate match for the contiguous United States was high, with the highest scores observed in the northern Midwest and in portions of the Rocky Mountain region. The certainty of assessment for N. tenuissima is low due to a still evolving understanding of the native range and lack of information pertaining to the history of invasiveness. The overall risk assessment category for N. tenuissima is uncertain.