Overview

Distribution

National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

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Global Range: Known only from one area in Texas in the headwaters of the San Marcos River; these plants were variously identified as Zizania aquatica or Z. palustris before being recognized as a distinct species by W. A. Silveus in 1932 (cf. Terrell et al., 1978) and subsequently described and named by Hitchcock in 1933.

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Historic Range:
U.S.A. (TX)

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Physical Description

Morphology

Physical Description

Perennials, Aquatic, growing in or on water, Aquatic, leaves floating on surface, Aquatic, fresh water, Terrestrial, not aquatic, Stolons or runners present, Stems trailing, spreading or prostrate, Stems nodes swollen or brittle, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems terete, round in cross section, or polygonal, Stem nodes bearded or hairy, Stem internodes solid or spongy, Stems with inflorescence 1-2 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 1-2 cm wide, Leaf blades 2 or more cm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule an unfringed eciliate membrane, Ligule elongated, 1-3 cm, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence curved, twisted or nodding, Inflorescence branches more than 10 to numerous, Lower panicle branches whorled, Flowers unisexual, Plants monoecious, Spikelets pedicellate, Spike lets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets unisexual, Spikelets falling with parts of disarticulating rachis or pedicel, Rachilla or pedicel glabrous, Monoecious - staminate and pistillate spikelets on same inflorescence, Glumes completely absent or reduced to cuplike structure, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 3 nerved, Lemma glabrous, Lemma apex acute or acuminate, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn 1-2 cm long, Lemma awned from tip, Lemma straight, Palea present, well developed, Palea about equal to lemma, Stamens 6, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.
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Dr. David Bogler

Source: USDA NRCS PLANTS Database

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Type Information

Holotype for Zizania texana Hitchc.
Catalog Number: US 1537174
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): W. Silveus
Year Collected: 1932
Locality: Hays, Texas, United States, North America
  • Holotype: Hitchcock, A. S. 1933. J. Wash. Acad. Sci. 23: 454.
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Isotype for Zizania texana Hitchc.
Catalog Number: US 1720531
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Original publication and alleged type specimen examined
Preparation: Pressed specimen
Collector(s): W. Silveus
Year Collected: 1932
Locality: Hays, Texas, United States, North America
  • Isotype: Hitchcock, A. S. 1933. J. Wash. Acad. Sci. 23: 454.
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Ecology

Habitat

Comments: A clear, flowing waters of spring origin with a relatively constant year-round temperature of 21-25 degress C. The plants grow in gravelly, sandy to silty clays in relatively shallow water (<2 m deep).

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 1 - 5

Comments: Known only from the one site in the headwaters of the San Marcos River at San Marcos, Texas.

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Zizania texana

The following is a representative barcode sequence, the centroid of all available sequences for this species.


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Source: Barcode of Life Data Systems (BOLD)

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Statistics of barcoding coverage: Zizania texana

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: N1 - Critically Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G1 - Critically Imperiled

Reasons: Endemic to the upper few km of the San Marcos River in south-central Texas, where it was locally abundant as recently as the the 1950s. It is now reduced to a precariously small population covering about 1200 square meters on an urbanized segment of the river. This remnant population rarely flowers or produces seed in the wild. The decline of this grass, which is narrowly adapted to high quality, aquifer-fed waters, is the result of drastic draw-downs in the aquifer level to support human population growth in the area, combined with past dredging and vegetation removal, damming, increased siltation and sewage loads, trampling and removal by recreationists, and herbivory by native and introduced waterfowl and by the non-native nutria. Efforts to establish new populations off the San Marcos River using cultivated plants have not been successful.

Environmental Specificity: Very narrow. Specialist or community with key requirements scarce.

Comments: Restricted to clear, cool, fast-flowing spring water (unusual in south-central Texas).

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Current Listing Status Summary

Status: Endangered
Date Listed: 05/27/1978
Lead Region:   Southwest Region (Region 2) 
Where Listed:


Population detail:

Listing status: E

For most current information and documents related to the conservation status and management of Zizania texana, see its USFWS Species Profile

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Global Long Term Trend: Decline of >90%

Comments: By 1967, this species had greatly declined in numbers and distribution extent along the upper San Marcos river since the 1930's (Emery, 1967), and continued to decline to a lesser degree, despite reduction in some threats, in the following decade (Emery, 1977; Terrell et al., 1978).

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Threats

Comments: Extremely limited distribution; one catastrophic event could eliminate entire species. While some historical threats are no longer significant, the species is in an urban area heavily used recreationally, and depends on continued flow of clean, cool spring water from the Edwards Aquifer.

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Wikipedia

Zizania texana

Zizania texana is a rare species of grass known by the common name Texas wild rice. It is endemic to Texas, where it is found only on the upper San Marcos River in Hays County. It is threatened by the loss and degradation of its habitat. It is a federally listed endangered species of the United States.[1][2]

This grass, a member of the same genus as commercially sold wild rice, is an aquatic plant that grows in the water with only its stem tips rising above the surface. It grows 1 to 2 meters long but the stems have been known to reach five meters in length. The ribbon-like leaves are up to a meter in length. The inflorescence is a panicle up to 31 centimeters long by 10 wide. The male spikelet is somewhat oval in shape and the female is lance-shaped with a long awn which may be a few centimeters in length.[3] The male and female flowers are on different branches of the panicle. Pollen is carried to other plants on the wind.[4] The plant can grow by cloning and sometimes forms mats of cloned stems.[2]

This plant is limited to a single site on the first two miles of the San Marcos River in Texas.[1] There are 140 clumps of stems in this population.[2] It covers about 1200 square meters.[5] There is also an introduced population at Spring Lake at the San Marcos Springs and a number of specimens are kept in an enclosure on the Texas State University campus.[2] The natural habitat of the grass is the clear water of the San Marcos River, which is fed by springs originating in the Edwards Aquifer.[5] The grass occurs in a relatively narrow range of water conditions, including temperature, pH, and turbidity, flow rates, and substrate types.[6]

This plant was once locally common in the area, growing thick enough to become a nuisance as recently as the 1930s. It has been reduced to its rare status because the Edwards Aquifer has been drained of its water for use in agriculture and other industries, lowering the flow on San Marcos River.[2] The rare plant is threatened now by recreational activities on the river, and by nutria, an introduced mammal.[1] Stems are broken, bent, or submerged by floating debris, including masses of vegetation mowed upstream and sent floating.[7]

The grass is inefficient in reproduction. It rarely accomplishes successful sexual reproduction. Pollen is released for a short time each day, typically only between 2 and 4 am. It is sometimes released a second time around 9 am. Within a few minutes the pollen loses its viability and it becomes nonfunctional within one hour.[4] Because the pollen is carried on the wind, the inflorescence must rise above the surface of the water; the stem cannot be broken or submerged. Pollen generally moves less than one meter from its parent inflorescence, so plants must be close together to reproduce and cannot be isolated. Today the plant is rare and the population is fragmented, making it difficult for the pollen to reach a receptive flower. The male flowers of the grass do not pollinate the female flowers on the same inflorescence because they do not release pollen at the same time the female flowers are receptive. The grass can also reproduce vegetatively by producing tillers. Tillers can break off and root to produce new stems, but these will be genetically identical to the parent plant.[4]

References[edit]

  1. ^ a b c Zizania texana. Texas Parks & Wildlife. Retrieved August 28, 2011.
  2. ^ a b c d e Zizania texana. Center for Plant Conservation. Retrieved August 28, 2011.
  3. ^ Zizania texana. Grass Manual Treatment. Retrieved August 28, 2011.
  4. ^ a b c Power, P. and F. M. Oxley. August 18, 2004. Assessment of factors influencing Texas wild-rice (Zizania texana) sexual and asexual reproduction. 2004 Final Report. Prepared for Edwards Aquifer Authority by the San Marcos National Fish Hatchery and Technology Center and the Lady Bird Johnson Wildflower Center. Retrieved August 28, 2011.
  5. ^ a b Zizania texana. The Nature Conservancy. Retrieved August 28, 2011.
  6. ^ Poole, J.; Bowles, D. E. (1999). "Habitat characterization of Texas wild-rice (Zizania texana Hitchcock), an endangered aquatic macrophyte from the San Marcos River, TX, USA". Aquatic Conservation: Marine and Freshwater Ecosystems 9 (3): 291. doi:10.1002/(SICI)1099-0755(199905/06)9:3<291::AID-AQC349>3.0.CO;2-E. 
  7. ^ Power, P. (1996). Direct and indirect effects of floating vegetation mats on Texas wildrice (Zizania texana). Southwestern Naturalist 41 (4) 462. Retrieved August 28, 2011.
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Names and Taxonomy

Taxonomy

Comments: A generally accepted species in a genus of about four species (two others widespread in North America, and another in Asia). Accepted by U.S. Fish and Wildlife Service (federal listing as endangered, 1978), Kartesz (1994 checklist and 1999 floristic synthesis), and Judziewicz et al. (checklist New World grasses, 2000). Described and named by Hitchcock in 1933. LEM 2Feb00.

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