New York Natural Heritage Program
Riverbank Quillwort
Isoetes riparia Engelm. ex A. Braun
Quillworts
Isoetes riparia Timothy G Howard
Family: Quillwort Family (Isoetaceae)

State Protection: Endangered
listed species are those with: 1) 5 or fewer extant sites, or 2) fewer than 1,000 individuals, or 3) restricted to fewer than 4 U.S.G.S. 7 minute topographical maps, or 4) species listed as endangered by U.S. Department of Interior.

Federal Protection: Not Listed

State Rarity Rank: S1
A State Rarity Rank of S1 means: This plant is endangered/critically imperiled in New York because of extreme rarity (typically 5 or fewer populations or very few remaining individuals) or is extremely vulnerable to extirpation from New York due to biological factors.

Global Rarity Rank: G5
A Global Rarity Rank of G5 means: This species is demonstrably secure globally, though it may be quite rare in parts of its range, especially at the periphery.


Did you know?
Nearly all quillwort species are notorious for their promiscuity. This causes identification and problems, and results in difficulties in understanding the relationships between species. Most Isoetes species are able to cross with at least one other Isoetes species, forming both fertile and sterile hybrids. These crossings have even resulted in new species. This is a complex group that challenges how one defines a species.

State Ranking Justification [-]
As of 2005, there are two known and verified populations. A population from Mohonk Lake was last reported in the late 1970s and there is no reason to suspect that it has disappeared. There are also reports of large populations on the Vermont side from the northern portion of Lake Champlain. In the early to mid 1900s, many populations were reported along the Hudson River but these appear to have completely disappeared. There are also historical records from the St. Lawrence Seaway that have not been observed in many years. This species may have been negatively impacted by water quality degradation, or this is a much overlooked species.

Short-term Trends [-]

Long-term Trends [-]