Eryngium arenosum
| Eryngium arenosum | |
|---|---|
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Embryophytes |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Asterids |
| Order: | Apiales |
| Family: | Apiaceae |
| Genus: | Eryngium |
| Species: | E. arenosum |
| Binomial name | |
| Eryngium arenosum C.I.Calviño & G.A.Levin | |
Eryngium arenosum, commonly known as the sand eryngo or Sand Sheet eryngo, is a rare species of flowering plant in the carrot family, Apiaceae. It is an annual herb endemic to the South Texas Sand Sheet of southern Texas. It grows chiefly in dry sandy grasslands and along the margins of mesquite woodlands, often near seasonal wetlands.[2][1]
The species was formally described in 2019 after herbarium specimens previously identified as Eryngium nasturtiifolium were found to represent a distinct taxon. It differs from that species in the form, color, size, and flower number of its flower heads, the morphology of its involucral and floral bracts, the absence of a terminal coma, its fruit scales, and its preference for sandy upland habitats.[3]
Description
Eryngium arenosum is a glabrous annual herb with a taproot. Its stems may be prostrate, ascending, or erect and branch from the axils of the stem leaves.
The leaves are herbaceous and pinnately lobed. Their margins are not thickened into the rigid, callous borders found in some related species. Basal leaves may wither by the time the plant is mature, while stem leaves remain distributed along the branches.
The inflorescence consists of small, sessile or nearly sessile flower heads borne in repeatedly branched clusters.. Each head is surrounded by spreading green bracts. The bract margins are entire rather than spiny.[4]
The small bisexual flowers are sessile within the heads. Each flower is subtended by a floral bractlet. Unlike E. nasturtiifolium, the central floral bractlets do not project beyond the head to form a conspicuous terminal tuft, or coma.[3]
The fruits divide into two one-seeded mericarps whose surfaces bear both scales and papillae. The enlarged calycine scales do not completely conceal the persistent sepals, another feature distinguishing the species from E. nasturtiifolium.[3][4]
Flowering and fruiting have been reported from March through September.[2]
Taxonomy
Eryngium arenosum was described by Argentine botanist Carolina I. Calviño and American botanist Geoffrey A. Levin in 2019. The description was published in volume 44 of the journal Systematic Botany.[3]
The name is cited as:
- Eryngium arenosum C.I.Calviño & G.A.Levin, Syst. Bot. 44(2): 447. 2019.[5]
The holotype was collected by Cyrus Longworth Lundell on 24 April 1949 in Kenedy County, Texas, south of Norias near U.S. Highway 77. It is deposited in the herbarium of the University of California, Berkeley, with isotypes at the Missouri Botanical Garden, United States National Herbarium, and Lundell Herbarium.[5]
The specific epithet arenosum is derived from Latin and means “sandy”, referring to the sandy soils and South Texas Sand Sheet habitat occupied by the species.[6]
Similar species
Eryngium arenosum was historically included within Eryngium nasturtiifolium, its closest morphological relative. Both species have small, pale flower heads that may be sessile or nearly sessile.[3]
Eryngium arenosum differs in having smaller, more nearly globose heads with fewer flowers, shorter involucral and floral bracts, and no terminal coma. Its calycine fruit scales are shorter relative to the sepals. It also grows primarily in sandy grasslands and mesquite woodland margins, whereas E. nasturtiifolium is more strongly associated with wet clay soils and aquatic or seasonally inundated habitats.[3]
It can also be distinguished from Eryngium diffusum, which has larger bluish-purple or gray-green heads, spiny involucral bracts, thicker leaves with callous margins, longer sepals, and fruits that are papillate but not conspicuously scaly.[4]
Distribution
Eryngium arenosum is endemic to southern Texas. It is principally restricted to the South Texas Sand Sheet, with some occurrences extending into the adjoining Gulf Coast Prairies and Marshes region.[1]
The 2026 Flora of the Southeastern United States records the species from Brooks, Cameron, Kenedy, Kleberg, Nueces, and Willacy counties.[2]
NatureServe estimates its total range extent at between 1,000 and 20,000 km2 (390 and 7,720 sq mi). The number of distinct occurrences is estimated to be between 6 and 80.[1]
Habitat and ecology
The species occurs in dry sandy grasslands and along the open margins of mesquite woodlands. It is frequently found near the edges of seasonal wetlands and temporary pools, nearly always on sand and only rarely on clay soils.[1]
The high heliophily rating assigned by the Flora of the Southeastern United States indicates a strong association with open, sunny habitats.[2] Suitable sites may include shallow depressions, sandy swales, open rangeland, and ecotones between grassland and mesquite scrub.
Although it is often associated with the margins of seasonally wet habitats, E. arenosum is characteristic of sandier and generally drier microsites than the closely related E. nasturtiifolium.[3]
The species is classified as a facultative wetland plant in both the Atlantic and Gulf Coastal Plain and Great Plains wetland regions. This designation reflects its frequent occurrence near seasonal wetlands, although it is not restricted to continuously wet soil.[2]
Conservation
NatureServe assigns Eryngium arenosum a global conservation rank of G2G3, indicating uncertainty between imperiled and vulnerable. Its rounded global rank is G2, or imperiled. The assessment was completed on 2 August 2019 using NatureServe's conservation-rank calculator.[1]
The species is ranked N2N3 in the United States. It has not yet been assigned a subnational conservation rank in Texas and has no status under the United States Endangered Species Act.[1]
Its conservation rank reflects its narrow distribution, restriction to specialized South Texas Sand Sheet habitats, and relatively small estimated number of occurrences. NatureServe recognizes between 6 and 80 occurrences, but detailed information on population sizes, trends, viability, and threats remains limited.[1]
Potential threats may include conversion of native sandy grasslands to agriculture or improved pasture, expansion of woody vegetation, alteration of seasonal wetland hydrology, road construction, intensive grazing, and development. However, the scope and severity of individual threats have not yet been fully assessed.
Additional field surveys are needed to determine the number and condition of populations, establish abundance and trend data, and clarify the species' response to grazing, fire, brush management, and changes in wetland hydrology.
References
- 1 2 3 4 5 6 7 8 "Eryngium arenosum". NatureServe Explorer. NatureServe. Retrieved 21 July 2026.
- 1 2 3 4 5 Weakley, Alan S.; Southeastern Flora Team (2026). "Eryngium arenosum". Flora of the Southeastern United States. Retrieved 21 July 2026.
- 1 2 3 4 5 6 7 Calviño, Carolina I.; Levin, Geoffrey A. (2019). "A new species of Eryngium (Apiaceae, Saniculoideae) from the USA". Systematic Botany. 44 (2): 446–450. doi:10.1600/036364419X15562052252261.
- 1 2 3 Flora of North America Editorial Committee (2024). Flora of North America North of Mexico. Vol. 13. New York and Oxford: Oxford University Press. pp. 1–566.
- 1 2 "Eryngium arenosum C.I.Calviño & G.A.Levin". International Plant Names Index. Royal Botanic Gardens, Kew; Harvard University Herbaria & Libraries; Australian National Herbarium. Retrieved 21 July 2026.
- ↑ "Eryngium arenosum C.I.Calviño & G.A.Levin". Plants of the World Online. Royal Botanic Gardens, Kew. Retrieved 21 July 2026.