Flora of North America species comparison

Ruppia spiralis Linnaeus has occasionally been used for this taxon in North America. Linnaeus, however, had never published that name (J. T. A. Verhoeven 1979). Ruppia cirrhosa is, indeed, the correct name for the taxon (J. C. Gamerro 1968).

An implication that the North American material with long, spiraling peduncles is different from the European material of Ruppia cirrhosa stems from the statement that R. occidentalis occurs in inland lakes (J. T. A. Verhoeven 1979). No differences between European R. cirrhosa and the North American material are listed, however. In fact, a comparison of the Verhoeven's descriptive discussions for of R. cirrhosa (Verhoeven 1979) with the North American material shows that the two are the same. The genus should be studied on a worldwide basis. Until further studies indicate otherwise, I am considering North American and European material to be conspecific.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Considerable confusion exists about North American taxa of Ruppia. Two distinct forms, along with several intermediates, are known: one with short peduncles with four or fewer spirals and another with long peduncles with five or more coils (often many more). Usually, those with few coils are in brackish waters near the coast, whereas those with many coils are inland, often in lakes that have high mineral contents. The forms have been considered variants variants of one species, R. maritima (M. L. Fernald and K. M. Wiegand 1914); more recently they have been accepted at species level (R. F. Thorne 1993). I am adopting Thorne’s concepts.

Species ca. 10 (2 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)