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Cyperus

Cyperus is a large of sedges in the family , comprising approximately 950 of and herbaceous distributed worldwide across tropical and temperate regions. These glabrous herbs typically inhabit wet or moist environments, such as wetlands, riverbanks, and disturbed areas, growing from a few centimeters to over a meter in height with erect, often triangular stems and basal linear leaves. Morphologically, Cyperus species are characterized by their tufted , terminal umbel-like inflorescences bearing spikelets with bisexual flowers, and small, trigonous achenes as fruits. The genus exhibits in growth forms, from rhizomatous perennials to short-lived annuals, and many are adapted to or semi- conditions. Ecologically, they serve as important primary producers in grasslands and wetlands, contributing to , water filtration, and providing for . Several Cyperus species hold economic and cultural significance. Cyperus papyrus, native to , has been historically used for making and is now valued in for its ornamental umbrella-like foliage. , known as chufa or yellow nutsedge, produces edible tubers consumed as a or in beverages, with notable production in regions like . Conversely, species such as (purple nutsedge) are among the world's worst weeds, causing substantial agricultural losses due to their aggressive rhizomatous spread. Additionally, various species provide materials for mats, medicines, and in traditional uses.

Taxonomy and Morphology

Morphological Characteristics

Cyperus species exhibit a range of growth forms, including annuals and perennials that are either tufted or rhizomatous, with some developing tubers or stolons; these can be terrestrial or , adapting to diverse environments through variations in structure. Stems, known as culms, are typically simple, erect, and scapose, arising from the base; they display either a triangular (trigonous) or circular cross-section and may be solid or spongy, with heights ranging from as short as 5 cm in small annuals to over 5 m in robust perennials. Leaves are predominantly basal, linear, and grass-like, arranged in three ranks (tristichous); they often appear reduced or absent in some , consisting mainly of sheaths without a , and their blades can be flat, V-shaped, or inrolled in cross-section. The is usually terminal, sometimes appearing pseudolateral, and forms compact heads or umbel-like (anthelate) clusters; it consists of arranged in dense or loose spikes or digitate groups, subtended by leaf-like bracts, with each containing distichous scales and small, greenish-brown, bisexual flowers lacking a . These flowers are wind-pollinated, featuring 1–3 stamens and a style that is 2- or 3-cleft with corresponding branched stigmas. Fruits are small achenes or nutlets, typically obovoid to , either trigonous or in shape, and smooth to tuberculate in texture; dispersal occurs primarily via or attachment to animals, including birds and waterfowl that carry them in mud or internally. Morphological variations are pronounced across growth forms: species tend to be shorter and more slender, with reduced leaves and simpler inflorescences, while perennials often have rhizomes or tubers for vegetative spread and sturdier stems; forms, such as those in wetlands, may feature spongy tissues for and roots that stabilize sediments in shallow water.

Taxonomic Classification

Cyperus belongs to the family , within the order , and is placed in the subfamily Cyperoideae and tribe Cypereae. This positioning reflects its close relationship with other sedge genera sharing traits like solid, triangular stems and spikelet-based inflorescences. The genus Cyperus was formally established by in his in 1753, where he described 17 species based primarily on morphological features such as structure and characteristics. Subsequent taxonomic revisions expanded and refined this framework; notably, Georg Kükenthal's comprehensive in 1935–1936 divided Cyperus into six subgenera—Eucyperus, Juncellus, Pycreus, , Kyllinga, and Torulinium—and 61 sections, emphasizing differences in arrangement, nutlet morphology, and vegetative habit. These divisions relied on synapomorphies such as the presence or absence of rhizomes, the compression of s, and floral scale vestiture, providing a morphological basis for classification that influenced subsequent work. Current taxonomic estimates recognize approximately 960 in Cyperus, a significant increase from earlier counts of around 700, driven by integrative approaches combining with molecular . Subgeneric divisions persist in modern frameworks, with key groups including subgenus Cyperus (featuring digitate inflorescences and compressed spikelets as synapomorphies) and subgenus Juncellus (distinguished by elongated, paniculate inflorescences and linear spikelets). These sections highlight evolutionary adaptations, such as the photosynthetic pathway in many tropical lineages, which serves as a synapomorphy for the monophyletic Cyperus . Recent taxonomic changes have broadened the genus circumscription, incorporating species from segregate genera like Kyllinga, Ascolepis, and Pycreus into Cyperus sensu lato based on phylogenetic analyses of and DNA sequences, which demonstrate their nested positions within the Cyperus . This revision, supported by shared morphological traits like bicarinate nutlets and similar embryo structures, resolves previous and aligns the with evolutionary relationships.

Distribution and Diversity

Global Distribution

The genus Cyperus exhibits a nearly , occurring across all continents except , with native ranges spanning , (both temperate and tropical), , , , and . This widespread presence is particularly pronounced in tropical and subtropical regions, where the majority of the approximately 960 thrive, reflecting the genus's to diverse environmental conditions. Africa serves as the center of origin and primary diversity hotspot for Cyperus, with the genus likely emerging there during the Early and undergoing significant diversification in the . In , Cyperus accounts for about 46% of the island's sedge flora, underscoring its Afrotropical core, while substantial populations also occur across the , , and , contributing to the genus's global footprint. Biogeographic patterns within Cyperus include notable Old World-New World disjunctions, such as amphitropical distributions observed in species like C. rigens, linking temperate and tropical zones across hemispheres. Island endemism is evident in regions like , where eight species in section Incurvi are restricted to the island, and , hosting native and endemic lineages amid broader Pacific distributions. Species of Cyperus associate with a broad climatic spectrum, from tropical wetlands and seasonal floodplains to temperate grasslands and disturbed sites, often in waterlogged or moist soils. Their altitudinal range extends from to over 3,000 meters in some cases, such as C. cyperoides in montane habitats. Dispersal mechanisms have facilitated this expansion, including hydrochory via water currents in riverine systems and anthropogenic transport through and trade, enabling long-distance migration across continents.

Species Diversity and Endemism

The Cyperus comprises approximately 960 worldwide, a count updated through recent taxonomic revisions and new discoveries that exceeds prior estimates of around 700 . This diversity reflects dynamic evolutionary processes, including shifts in rates documented in recent phylogenetic studies, which indicate higher net diversification in C4 photosynthetic lineages compared to C3 ones. Hybridization has further influenced , particularly in adaptive radiations and polyploid complexes within the . High species diversity characterizes tropical regions, with hotspots in —where hundreds of species occur across tropical and subtropical zones—and island systems like and the . serves as a primary center of variation, supporting extensive native assemblages in and habitats. In , endemism is notable, with at least eight species restricted to the island in Cyperus section Incurvi alone, alongside other localized taxa adapted to highland forests and . The islands host endemic Cyperus forms, such as C. stewartii on , contributing to regional biogeographic uniqueness amid broader tropical distributions. Patterns of are especially evident in oceanic archipelagos, exemplified by the Hawaiian Cyperus , which has produced eight endemic species from an initial colonist, representing half of the 14 native Hawaiian taxa and highlighting rapid adaptive in isolated volcanic habitats. Threatened endemics include Cyperus papyrus subsp. hadidii, an subspecies once presumed extinct but rediscovered, now classified as endangered due to severe habitat degradation. Overall, the assesses around 20 Cyperus species as threatened (, Endangered, or Vulnerable), with primary threats stemming from habitat loss via drainage, agricultural conversion, and encroachment; notable examples encompass C. prophyllatus (Endangered, restricted to a single Mexican locality), C. nervulosus (Vulnerable in ), and C. trachysanthos (threatened in Hawaiian s). These vulnerabilities emphasize the need for targeted to preserve the genus's endemic diversity.

Ecology and Reproduction

Habitats and Ecological Roles

Cyperus species are primarily adapted to habitats, thriving in environments with high such as marshes, swamps, riverbanks, and disturbed areas like paddies. Many exhibit a range from fully aquatic forms, such as Cyperus papyrus in tropical floodplains, to semi-terrestrial varieties in seasonally wet soils. These preferences stem from their tolerance for saturated conditions, allowing colonization of both natural wetlands and anthropogenic sites like irrigated fields. In ecosystems, Cyperus plays vital roles in maintaining functionality, including stabilization via dense networks that bind soils and reduce during floods. These plants also enhance through filtration, absorbing excess nutrients, , and pollutants from water and s, thereby supporting in aquatic systems. Furthermore, species like C. papyrus contribute to by accumulating organic matter in soils, acting as long-term sinks in tropical s. Cyperus interacts with as a source, with tubers and foliage consumed by birds, mammals, and larvae of certain species, bolstering webs in marshy habitats. Conversely, it competes intensely with crops in agricultural ecosystems, depleting and nutrients while releasing allelopathic compounds that suppress neighboring growth. Adaptations such as in —achieved through resilient tubers that endure dry spells—and flood resistance via efficient oxygen transport in aerenchymatous tissues enable persistence across variable conditions. C. rotundus exemplifies invasive tendencies as a widespread , altering community dynamics in invaded areas.

Reproduction and Life Cycle

Cyperus species display a combination of sexual and reproductive strategies, enabling to diverse environments. Flowering occurs in compact spikelets, typically 1–150 per , with bisexual flowers (rarely unisexual) subtended by distichous floral scales. These spikelets are wind-pollinated, characteristic of the family, where reduced flowers produce abundant nonsticky pollen for anemophily. In temperate zones, flowering is seasonal, often peaking in summer to early fall, aligning with favorable growth conditions. Pollination in Cyperus is predominantly anemophilous, with serving as the primary due to the inconspicuous nature of the flowers and lack of specialized attractants. Fertilization follows typical monocot patterns, involving 1–3 stamens and 2–3-fid styles with corresponding stigmas, leading to development. vectors are rare but documented in some , representing a derived from the family's ancestral . Seed production results in small, biconvex to trigonous nutlets (achenes), often with wings at the base. These seeds exhibit dormancy mechanisms influenced by environmental cues such as , fluctuations, and oxygen levels, promoting persistent seed banks. Viability can persist for several years, with maximum recorded longevities exceeding a decade in , though many lose viability within 1–3 years depending on conditions. Aquatic species may benefit from water-aided dispersal of these buoyant nutlets. Vegetative reproduction is prevalent, particularly in perennial species, via rhizomes, stolons, or tubers that facilitate clonal propagation and rapid spread. For instance, Cyperus esculentus produces tubers that enable extensive underground growth and regeneration. The life cycle varies by species: annuals, such as Cyperus difformis, complete their cycle in one season, from germination through flowering and seed set in as little as 4–6 weeks. Perennials, like Cyperus rotundus, rely on both sexual reproduction and persistent clonal growth via rhizomes, allowing multi-year persistence and vegetative dominance.

Evolutionary History

Fossil Record

The fossil record of Cyperus begins in the Middle Miocene, with the earliest genus-specific evidence consisting of achenes and spikelets preserved in lacustrine and fluvial deposits. In , numerous fossil fruits identified as Cyperus sp. have been recovered from Middle Miocene sediments (approximately 15–13 Ma) in the Fasterholt area near , Central , , where they occur alongside other angiosperm remains indicative of a warm-temperate, -influenced flora. Similarly, fruits of †Cyperus distachyoformis (originally described as Acorellus distachyoformis) were extracted from borehole samples of Middle Miocene freshwater deposits in the Nowy Sącz Basin, West Carpathians, , representing compressed achenes with characteristic triangular outlines and reticulate surfaces typical of the genus. These European finds highlight Cyperus as part of diverse wetland assemblages. In , the genus is documented by spikelets assigned to Cyperus sp. from deposits in , where fossils up to 2 cm long preserve distichous florets on rachillae, suggesting growth in marshy, subtropical environments. Stem impressions are rarer but occur in some assemblages, often as compressed rhizomes or culms from sediments. The known geographic of Cyperus fossils is limited to Europe and , with no confirmed records from other continents during the , reflecting taphonomic biases that hinder preservation in the habitats preferred by sedges—such as rapid decay in waterlogged soils and low rates in marshes. This sparsity underscores the challenges in reconstructing the genus's early history, as Cyperus likely inhabited similar ephemeral environments that rarely fossilize completely. These Miocene occurrences imply a crown age for Cyperus of approximately 30–40 million years, aligned with fossil-calibrated molecular estimates placing the genus's diversification in the late Eocene to early , shortly after the radiation of core lineages. Pre- Cyperus fossils remain absent, with the record relying on broader evidence, such as Eocene fruits and pollen from mapanioide sedges in , which indicate the family's establishment in wetlands but predate genus-level diversification in Cyperus.

Phylogenetic Insights

Molecular phylogenetic studies of Cyperus have utilized markers such as the (ITS) region of nuclear ribosomal DNA and the chloroplast matK gene to reconstruct evolutionary relationships within the and its allies. These analyses have demonstrated that Cyperus sensu lato is monophyletic, encompassing approximately 960 species, though early investigations revealed in the traditional circumscription due to embedded segregate genera. The structure of Cyperus distinguishes a group of Cyperus species, primarily C4 photosynthesizing taxa, from 13 segregate genera (e.g., Pycreus, Kyllinga) that are phylogenetically nested within it, forming the broader Cyperus in tribe Cypereae. This structure highlights area-richness correlations, with higher in African and Neotropical linked to historical dispersal patterns rather than isolated radiations. Diversification bursts occurred during the , coinciding with the evolution of C4 in the Early , which elevated net diversification rates in affected lineages compared to C3 relatives. Divergence timelines indicate an origin for Cyperus in the Early (approximately 34 million years ago), with subsequent radiations in the and between 10 and 20 million years ago driven by long-distance dispersal events from . Evolutionary drivers include shifts from to drier habitats associated with and polyploidy events, which facilitated to diverse soil conditions and contributed to rate shifts. Fossil calibrations from nodes support these dating estimates. Recent studies from 2023 to 2025 have refined the biogeographic framework, integrating multi-locus data to resolve relationships across the genus and emphasizing recurrent dispersals as key to its global distribution and diversity.

Human Uses and Impacts

Traditional and Modern Uses

Cyperus species have been utilized by for millennia, with C. papyrus playing a central role in ancient society. Dating back to the Predynastic period (before ca. 3100 BCE), crafted lightweight skiffs from bundled stalks of C. papyrus for transportation and hunting along the , as depicted in early tomb art. By around 2900 BCE, the pith of the stems was processed into sheets, the world's first widespread writing material, used for administrative documents, religious texts, and letters. The durable outer rinds were stripped into fibers for constructing mats, baskets, ropes, and sandals, with examples of such items preserved from the 18th Dynasty (ca. 1390–1352 BCE). In various indigenous cultures, stems and leaves of multiple Cyperus species have been woven into practical items due to their strong, fibrous nature. For instance, C. textilis in , particularly among the Khoi people, is traditionally used to create mats for hut coverings and rolled . Similarly, species like C. laevigatus and C. latifolius are employed in , , and for baskets, hats, and sleeping mats, highlighting their regional economic and cultural significance in crafting. Several Cyperus species serve as food sources, notably C. esculentus, whose tubers—known as tiger nuts—have been consumed in and for their nutritional value. These tubers are rich in monounsaturated fats, particularly (65–69% of total fatty acids), and provide high (about 9 grams per 28-gram serving), along with minerals like , magnesium, and iron. Traditionally eaten raw, roasted, or in beverages like in Mediterranean regions with African origins, they support digestion and energy needs. Medicinally, C. rotundus (nutgrass) has been employed in traditional systems like , where its rhizomes, known as musta, act as a and absorbent for digestive disorders such as and stomach ailments. Extracts from the rhizomes exhibit properties, reducing paw in animal models comparably to indomethacin, and are applied externally to alleviate and itching. These uses stem from ancient texts like the , integrating the plant into remedies for bowel issues and fevers. Ornamentally, C. alternifolius (umbrella plant) is widely cultivated as a for its distinctive umbrella-like bracts atop tall stems, thriving in moist indoor conditions and adding a tropical aesthetic to homes or terrariums. Native to , it requires consistent moisture and indirect light, making it suitable for beginners in water-feature setups. In modern applications, Cyperus species contribute to and . C. papyrus is integrated into constructed wetlands for , effectively removing up to 80% of , 70% of , and over 90% of like and from , while also eliminating 96–99% of . Additionally, its abundant in sub-Saharan African wetlands is explored for production, such as compressed briquettes for cooking and heating, offering a sustainable alternative to wood fuels.

Invasive Species and Conservation

Several species within the genus Cyperus are recognized as invasive weeds, with C. rotundus (purple nutsedge) being the most notorious, infesting agricultural lands in over 90 countries and ranking as the world's worst weed due to its persistence and crop competition. This species causes yield reductions of 20–90% in crops such as , , and through resource competition and , leading to substantial economic impacts on global . Other notable invasives include C. esculentus (yellow nutsedge), which similarly proliferates in disturbed soils and waterways, and C. difformis, a problematic in . The spread of invasive Cyperus is facilitated by their extensive rhizomatous and tuberous growth, enabling rapid ; a single C. rotundus can produce up to 10–30 million tubers per annually, surviving depths of up to 80 cm. Human-mediated dispersal occurs via contaminated agricultural equipment, crop seeds, and , exacerbating invasions in new regions. Control strategies emphasize integrated management, including chemical herbicides like and halosulfuron for tuber suppression, physical methods such as , and biological agents like the Dactylaria higginsii, which achieves up to 90% efficacy with repeated applications. While many Cyperus species are invasive, others face conservation challenges due to habitat degradation, particularly in wetlands where drainage and pollution threaten endemic taxa. C. microcristatus, restricted to montane wetlands in , has been assessed as owing to restricted range and habitat loss from agricultural expansion. In , endemics such as C. ankaratrensis hold Endangered status, impacted by and wetland conversion for paddies, with six of eight species in section Incurvi assessed as threatened. efforts, including ecohydrological interventions to revive papyrus-dominated wetlands, indirectly benefit vulnerable Cyperus by stabilizing and reducing . Recent studies in the highlight how enhances the invasiveness of C. rotundus, with variations in showing adaptations to local climates that boost sprouting and resistance. projections indicate that elevated temperatures (up to +4°C) and altered moisture regimes could expand C. rotundus ranges, intensifying its threat during wet seasons, while simultaneously stressing habitats critical for .