Eleocharis aestuum (Cyperaceae), a New Tidal River Shore Spikesedge of the Eastern United States

Abstract

Eleocharis diandra is an annual spikesedge of northeastern U.S. river and lake shores. This species has a complicated taxonomic history and has been included in the synonymy of other members of the Eleocharis ovata complex by various researchers. Its differing applications are due, in part, to the existence of a previously un¬ described taxon. The new species Eleocharis aes¬ tuum is described from the eastern United States and is restricted to freshwater tidal river commu¬ nities. This species is similar to E. diandra in its marked absence or reduction of perianth bristles, but it differs in floral scale and tubercle morphol¬ ogy. Despite limited regional variation in morphol¬ ogy, E. aestuum is morphologically separable from other spikesedges throughout its range. Recognition of this new species reveals that E. diandra is geo¬ graphically restricted and globally imperiled. Con¬ servation action is needed for both species.