Rhynchospora

Rhynchospora (beak-rush or beak-sedge) is a genus of about 400 species of sedges with a cosmopolitan distribution. The genus includes both annual and perennial species, mostly with erect 3-sided stems and 3-ranked leaves. The achenes bear a beak-like tubercule (hence the name “beak-rush”, although the plants are sedges, not rushes) and are sometimes subtended by bristles. Many of the species are similar in vegetative appearance, and mature fruits are needed to make a positive identification.^{[1] [2]}

Beak-sedge
Rhynchospora fascicularis
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Monocots
Clade:	Commelinids
Order:	Poales
Family:	Cyperaceae
Genus:	Rhynchospora Vahl
Type species
Rhynchospora alba (L.) Vahl.
Synonyms[1]
Asteroschoenus Nees Astroschoenus Lindl. Calyptrolepis Steud. Calyptrostylis Nees Cephaloschoenus Nees Ceratoschoenus Nees Cleistocalyx Steud. Dichroma Ham. Dichromena Michx. Diplochaete Nees Echinoschoenus Nees & Meyen Ephippiorhynchium Nees Eriochaeta Torr. ex Steud. Haloschoenus Nees Haplostylis Nees Hygrocharis Nees Kleistrocalyx Steud. Leptoschoenus Nees Lonchostylis Torr. Microchaeta Rchb. Micropapyrus Suess. Mitrospora Nees Morisia Nees Nemochloa Nees Nomochloa Nees Pachymitra Nees Phaeocephalum Ehrh Pleurostachys Brongn. Psilocarya Torr. Pterochaete Arn. ex Boeckeler Pterotheca C.Presl Ptilochaeta Nees Ptilosciadium Steud. Spermodon P.Beauv. ex Lestib. Sphaeroschoenus Nees Syntrinema H.Pfeiff. Trichochaeta Steud. Triodon Pers. Zosterospermon P.Beauv. ex Lestib.

The inflorescences (spikelets) are sometimes subtended by bracts which can be leaf-like or showy.^[3][4]

Members of this genus have holocentric chromosomes and have become a model for the study of chromosome evolution and meiotic recombination in holocentric plants.^[5] The genomes of Rhynchospora pubera, R. breviuscula, and R. tenuis have been published in 2022.^[6]

Ecology

Rhynchospora occurs on all continents except Antarctica, but is most diverse in the neotropics.^[7] It is most frequent in sunny habitats with wet, acidic soils.^[8] In marshes and savannas, Rhynchospora may be the dominant form of vegetation.

Taxonomy

See also: List of Rhynchospora species

Contemporary taxonomic treatments include Rhynchospora and the related genus Pleurostachys in the tribe Rhynchosporae, a well-supported clade within Cyperaceae.^[9] The most comprehensive monograph of the genus ^[10] divides Rhynchospora into two subgenera and 29 sections. A recent molecular analysis ^[11] identifies two primary clades within the genus, with well-supported subgroups that agree with several of the sections identified by Kükenthal. However, this molecular analysis also suggests that Pleurostachys is embedded within one of the primary clades of Rhynchospora and that several of the recognized sections are not monophyletic.^[11]

Selected species

^[1]

• Rhynchospora alba - White beak-sedge. Europe, North America
• Rhynchospora caduca - Southeast North America
• Rhynchospora californica - California beaked-rush, occurring in Marin and Sonoma County, California
• Rhynchospora capillacea - Slender beakrush. Eastern North America
• Rhynchospora capitellata - Brownish beak-sedge
• Rhynchospora colorata - White star sedge. Southeast North America.
• Rhynchospora fusca - Brown beak-sedge. Europe.
• Rhynchospora glomerata - Clustered beak-sedge. North America.^[12]
• Rhynchospora inexpansa - Southeastern North America and West Indies
• Rhynchospora knieskernii - Knieskern's beak-sedge.
• Rhynchospora longisetis
• Rhynchospora macrostachya - Tall horned beaksedge. Eastern North America.
• Rhynchospora megalocarpa - Southeastern United States
• Rhynchospora megaplumosa - Florida
• Rhynchospora nervosa - Tropical New World.
• Rhynchospora rariflora - Southeastern North America, West Indies, Central America
• Rhynchospora scirpoides - North America
• Rhynchospora waspamensis - New World.