Quillwort

Shore Quillwort

Isoetes canadensis (Engelmann) A.A. Eaton Isoetes dodgei A. Eaton [This probably reflects a hybridization between Isoetes riparia and Isoetes echinospora.] Isoetes riparia var. canadensis Engelm. Isoetes riparia var. robbinsii (A. Eaton) Proctor

Isoetes riparia var. amesii (A.A. Eat.) Proctor Isoetes riparia var. riparia Isoetes saccharata Engelm. Isoetes saccharata var. amesii A.A. Eat.

Isoetes riparia appears to be an allotetraploid (2n=44), meaning that it is a species of hybrid origin where the chromosomes doubled after the initial hybridization to produce a new fertile species. The original parents were likely Isoetes echinospora and Isoetes engelmannii. The hybrid between this two species is typically called Isoetes x eatonii. Isoetes x eatonii is the sterile hybrid between these parents, while Isoetes riparia probably resulted from the doubling of chromosomes within Isoetes x eatonii. Isoetes riparia may hybridize with Isoetes echinospora, Isoetes engelmanii, Isoetes lacustris, or Isoetes tuckermanii (Flora of North America 1993).