Najas flexilis

This record represents the narrow concept of Najas flexilis which excludes N. canadensis as a distinct species, following Les et al. (2015) who say, "Although previously recognized as a single, wide-ranging taxon, Najas flexilis s.l. comprises two genetically distinct, sibling species, to which the names N. flexilis and N. canadensis can be applied. The two species differ subtly by their seed morphology, with thicker seeds in the former and thinner seeds in the latter. However, their distinction by seed morphometry is difficult unless data are compared statistically, which leads us to designate them as cryptic species. The thick and thin seed phenotypes correspond cytotypically as diploid (N. flexilis) or tetraploid (N. canadensis)." VASCAN (Brouillet et al. 2024) recognizes the two species as distinct. Haynes' treatment in FNA (2000, vol. 22) includes N. canadensis in N. flexilis.

Najas flexilis is an aquatic annual herb widely distributed in North America. With a large range extent, more than 80 occurrences, abundant habitat, and broad habitat preferences, this species is considered secure.

Najas flexilis is an aquatic plant found across North America from Alaska south to Utah and east to Connecticut and Quebec. Range extent was estimated using herbarium specimens and photo-based observations documented between 1993 and 2024 and mapped locations in the paper describing N. canadensis (GBIF 2024, iNaturalist 2024, SEINet 2024, Les et. al 2015).

Despite Najas canadensis being split from Najas flexilis and the difficulty of distinguishing between the two species, there are likely more than 80 occurrences of the narrower concept of Najas flexilis (Les et al. 2015).

Although threats are not widely documented, Najas flexilis is potentially threatened by development, water pollution, use of aquatic herbicides, invasive species, and other threats in some places. However, their overall impact is likely negligible given the species' broad range, large number of occurrences, tolerance of light disturbance, and affinity for typically abundant habitats, as well as no obvious intrinsic vulnerabilities.