Flora of North America species comparison

Eleocharis acicularis is abundant and ecologically important throughout much of its range. It occurs in a wide variety of habitats, including acid waters. I have not seen voucher specimens for reports from Alabama and Florida. I have not seen vouchers for the reported chromosome numbers of 2n = 30–38 or 50–58.

Eleocharis acicularis often forms large rooted mats or floating masses, which when submerged, are often non-flowering. Submerged, usually nonflowering plants are abundant throughout much of the range of the species (H. K. Svenson 1929; P. E. Rothrock and R. H. Wagner 1975). They have been called E. acicularis forma fluitans (Doellinger) Svenson; E. acicularis forma inundata Svenson; E. acicularis forma longicaulis (Desmazières) Hegi; E. acicularis forma submersa (Nilsson) Norman; and E. acicularis var. submersa (Nilsson) Svenson. The culms of the submerged plants are terete, smooth, soft to flaccid, translucent, and the partitions of the air cavities within are clearly visible. Submerged plants may closely resemble aquatic forms of some other species, especially Eleocharis parvula, E. robbinsii, and Schoenoplectus subterminalis (Torrey) Sojak (N. C. Fassett 1957; E. G. Voss 1967, 1972–1996, vol. 3).

Although E. acicularis is very variable, recognition of varieties is premature pending a worldwide taxonomic revision of subg. Scirpidium. Much of the variation is apparently due to phenotypic plasticity in response to environmental factors, especially water depth (P. E. Rothrock and R. H. Wagner 1975). The named varieties intergrade extensively, and achenes, which are important in defining the varieties, are often absent. H. K. Svenson (1929) recognized four varieties and two forms for North America, but later (1957) did not recognize infraspecific taxa.

Most plants from the Arctic to cool-temperate North America, including higher elevations in the Southwest, are very similar to plants from northern Europe and presumably belong to typical E. acicularis, which was described from Europe. Those plants have culms cylindric or three- to four-angled; leaf sheaths mostly obscure and closely sheathing; and achenes about two times longer than wide.

Eleocharis acicularis var. gracilescens Svenson, type from St. Louis, Missouri, applies to plants with flowering culms unusually long (to 60 cm), smooth or sometimes with five to twelve fine ridges, their bases not cormlike; spikelets often linear-lanceoloid, often unusually long (to 8 mm); floral scales often unusually long (to 3.5 mm), often stramineous; and achenes much less than two times longer than wide. Plants of E. acicularis var. gracilescens are probably usually emergent in shallow water; they are known from scattered collections from Alabama, Florida, Kansas, Missouri, North Dakota, Oklahoma, South Carolina, Tennessee, and Texas. Robust plants of E. acicularis var. gracilescens are sometimes misidentified as E. wolfii. H. K. Svenson (1957) stated that var. gracilescens may be distinct from E. acicularis. Some specimens from California and Oregon that resemble E. acicularis var. gracilescens may be ecologic forms of E. acicularis var. occidentalis.

Eleocharis acicularis var. occidentalis Svenson, type from Santa Barbara, California (illustrated in H. L. Mason 1957; H. K. Svenson 1939, plate 539), applies to plants with culms only 2–6 cm, smooth or usually some prominently four-angled or finely to ca. eight-ridged, their bases often persistent, swollen, and cormlike (illustrated herein); distal leaf sheath summits mostly evident, often markedly inflated; achenes much less than two times longer than wide. This variety often grows in vernal pools. As here defined, it is known only from Arizona, California, and Nevada. Most of the specimens H. K. Svenson (1929) cited in the protologue and identified on herbarium specimens as E. acicularis var. occidentalis are probably referable to typical E. acicularis.

Eleocharis acicularis var. porcata S. G. Smith (S. G. Smith 2001), type from Texas, applies to plants that are similar to E. acicularis var. occidentalis except that their culms (cross section illustrated herein) reach 22 cm × 0.5 mm, some or all are prominently six- to twelve-ridged and mostly distinctly compressed, and their bases are not cormlike. This variety grows in mud and shallow water of marshes, ponds, and stream margins; it is known from Alberta, Arizona, Colorado, Illinois, Kansas, Louisiana, Nebraska, New Mexico, North Dakota, and Texas. Because of their compressed, prominently-ridged culms, robust plants of E. acicularis var. porcata, including a paratype of E. wolfii, are sometimes misidentified as E. wolfii (S. G. Smith 2001).

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

The markedly different chromosome counts reported from North America (2n = 12, from the Queen Charlotte Islands, British Columbia) and from Asia (2n = 38–40, 42, 56) suggest that more than one taxon should be recognized within Eleocharis kamtschatica as currently broadly defined. The three similar species E. kamtschatica, E. komarovii, and E. sachalinensis have been recognized for Russia (I. D. Zinserling 1935); more recent authors have recognized only E. kamtschatica (T. V. Egorova 1981 and A. E. Kozhevnikov 1988, for the former U.S.S.R.; J. Ohwi 1965, for Japan; S.-O Strandhede 1967; E. Hultén 1968 for Alaska; Tang T. and Wang F. T. 1961, for China). Pending a taxonomic revision, the following five names, all from eastern Asia, should probably be treated as synonyms of E. kamtschatica: E. komarovii Zinserling, E. mitrata (Franchet & Savatier ex Makino, E. sachalinensis (Meinschauser) B. Fedtschenko, E. savatieri Svenson, and E. triflora Komarov, not E. triflora Boeckeler. In E. kamtschatica in the broad sense, the size and form of the achenes and tubercles, on which most of the probable synonyms listed above are based, and the form of the distal leaf sheath summits do not seem to be correlated with each other or with other characters. In North America E. kamtschatica is known only from coastal habitats; in Asia it also occurs inland, especially around hot springs.

North American plants of Eleocharis kamtschatica seem to be separable into two groups: (1) Smaller plants, with culms mostly shorter than 20 cm, spikelets 5–13 × 3–4 mm, and floral scales 2.5–4 mm are known from about 20 localities on the Pacific Coast from Kodiak Island, Alaska, to the Queen Charlotte Islands and Prince Rupert, British Columbia, as well as from Hudson Bay in Manitoba, James Bay and the Gulf of St. Lawrence in Quebec, and Labrador. These small plants include the voucher specimens of the 2n = 12 chromosome count from British Columbia, and seem to fit E. kamtschatica as described by I. D. Zinserling (1935). (2) More robust plants, with culms mostly 20–70 cm, spikelets 7–20 × 4–6 mm, and floral scales 4–5 mm, are known from about 12 localities from Norton Sound in west-central Alaska to central British Columbia. These robust plants fit the descriptions of E. sachalinensis by I. D. Zinserling(1935), of E. savatieri Svenson from Japan (H. K. Svenson 1939), and of E. kamtschatica as described by J. Ohwi (1965), and are very similar to several specimens from Japan that I have seen.

Because Eleocharis kamtschatica closely resembles E. uniglumis except for size of the tubercles, plants without achenes cannot be reliably identified to species. The floral scales and receptacles in E. kamtschatica are very sparsely placed, with only 1–2 scales per mm of rachilla, compared with 3–4 mm of rachilla in most North American plants of E. uniglumis. Some North American collections, e.g., from the Kobuk sand dunes in northwestern Alaska, as E. uniglumis, and James Bay in Quebec, as E. kamtschatica, are intermediate between E. kamtschatica and E. uniglumis in the relative sizes of the tubercles and achenes.

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