Xylosma tweediana

Xylosma tweediana
A photo by Facundo Chieffo of Xylosma tweediana displaying its leaves and immature fruits.
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Malpighiales
Family:	Salicaceae
Genus:	Xylosma
Species:	X. tweediana
Binomial name
Xylosma tweediana (Clos) Eichler
Synonyms[Note 1][5][6]
List Hisingera tweediana Clos Myroxylon grayi Warb. Myroxylon tweedianum (Clos) Kuntze Myroxylon tweedieanum (Clos) Kuntze [2] Myroxylon tweedyanum (Clos) Kuntze Myroxylon warburgii Briq. Xylosma ciliatifolium auct. Xylosma grayi Gilg [2] Xylosma grayi (Warb.) Gilg Xylosma nitidum auct. Xylosma salzmanii auct. Xylosma sleumeri Herter Xylosma tweediana (Clos) Eichlam Xylosma tweedianum (Clos) Eichler Xylosma tweedieanum (Clos) Eichler [3] Xylosma venosa var. populneum Sleumer [4] Xylosma venosum var. populneum Sleumer ex Lombardo Xylosma warburgii (Briq.) Briq.

Xylosma tweediana, colloquially known as sucará,^[5] is a species of flowering plant in the family Salicaceae, endemically distributed throughout South America.

Xylosma tweediana is a ramified shrub or tree, ranging from 2–5 m (6 ft 7 in – 16 ft 5 in) in height, typically featuring a globose crown when mature. It commonly bears stout, simple spines on its main branches that may reach up to 5 cm (2.0 in), while the reddish branchlets, which are marked by circular lenticels, are initially patently puberulent, becoming early glabrescent and may be unarmed or equipped with slender axillary spines no longer than 2 cm (0.79 in). Spines are frequently reddish and appear singly per node, with larger, branched spines occasionally present on the trunk. Its glabrous, shiny leaves are elliptic to subovate or rhombic-elliptic, typically 3–4.5 cm (1.2–1.8 in) long and 1.5–2.5 cm (0.59–0.98 in) wide. Leaf apices are broadly subacuminate or obtuse, and the bases taper attenuately into slender, flexuous petioles, which are initially puberulent, and measure 5–8 mm (0.20–0.31 in). The margins are coarsely glandular-crenate with shallow venation and 6–7 irregular, steeply ascending lateral nerve pairs that branch near the edges. Leaf coloration may shift to reddish tones in autumn, and its foliage is generally deciduous. Leaves may be periodically deciduous, especially in the southern part of its distribution, and often emerge alongside the flowers. Flowers arise precociously from the axils of fallen leaves on annotinous branchlets. Male inflorescences are loosely clustered, while female ones are more compact, often subtended by numerous scarious bracts with dorsal pubescence. Peduncles are filiform and pedicels measure 3–4 mm (0.12–0.16 in), typically puberulous at anthesis. Flowers typically occur in fascicles comprising 3–8 individual units. Sepals number 4–5, and are ovate, subacute, dorsally short-pubescent but densely and long-ciliate internally. The hypogynous disc is extremely short and formed by 6–10 minute glands. Male flowers possess 15–25 glabrous filaments up to 4 mm (0.16 in) long with extrorse, biloculate anthers that are dorsally affixed. Female flowers are normally devoid of stamens, though vestigial ones have been sighted. Their sepals are ovate-cordate and decussately arranged in opposite pairs, glabrous externally and hairy within. The ovary is elongate-ovoid, glabrous, and unilocular, tapering into two smooth, erect styles that diverge apically. Stigmas are bifid, occasionally numbering up to 3, and may be subcapitate or reniform, reflexed and papillate.The fruit is described as a shiny, blackish-red berry roughly 4–5 mm (0.16–0.20 in) in diameter, containing 2–5 angular-ovoid seeds up to 3 mm (0.12 in) long. Though herbarium specimens suggest sexual dimorphism in armature, with unarmed male branches and spiny female ones, this feature is not uniformly expressed.^{[2][3][7][8][9][10]}

Xylosma tweediana is endemic to southern South America, spanning Argentina, Brazil, and Uruguay. In Argentina, its extent includes the northeastern provinces of Chaco, Corrientes, Entre Ríos, and Misiones. Within Brazil, it is found primarily in the southeastern state of São Paulo and the southern states of Rio Grande do Sul and Santa Catarina. In Uruguay, the species is widely distributed, recorded in departments such as Artigas, Canelones, Cerro Largo, Colonia, Durazno, Flores, Florida, Lavalleja, Maldonado, Montevideo, Paysandú, Río Negro, Rivera, Rocha, Salto, San José, Soriano, Tacuarembó, and Treinta y Tres. Though not explicitly stated to have been introduced outside of its native range, it has been preserved in Mexico.^[11][12]

Xylosma tweediana is a plant of the seasonally dry tropical biome and is commonly found at forest margins and within gallery forests, particularly on sandy soils at elevations of approximately 50–900 m (160–2,950 ft). In the Serras de Sudeste, it typically occurs as scattered seedlings in medium to large patches of woody vegetation, often coexisting with species characteristic of later successional stages rather than the pioneers that dominate smaller fragments. A survey on the South Plateau of Santa Catarina recorded it among regenerating plants in a cloud forest fragment, though it was absent from the adult tree inventory. This pattern suggests that Xylosma tweediana responds to recent disturbances such as grazing and logging, establishing itself in canopy gaps where increased light availability supports the recruitment of climax species during periods of structural reorganization.^{[2][9][13][14][15][16]}

Xylosma tweediana was originally described by Dominique Clos in 1857 as Hisingera tweediana. In 1871, August W. Eichler reassigned the species to Xylosma, naming it Xylosma tweedieanum, a designation later standardized to Xylosma tweedianum. A subsequent attempt in 1891 to transfer the species to Myroxylon was later synonymized, and the genus change was not adopted. Friedrich Eichlam, cited as the author by Plants of the World Online and World Flora Online, is a mistake likely stemming from a taxonomic misattribution or typographical error.^{[2][3][10][13]} Later, the genus underwent a grammatical gender concordance, initiated by William T. Stearn in 1992 when he questioned the genus’s gender, and finalized by Dan Henry Nicolson in 1994, putting Xylosma tweediana in agreement with the genus name.^[17][18] The collective number of synonyms across different sources is approximately 18.^{[Note 1]}

Historically, Xylosma tweediana was placed in Flacourtiaceae under older classification systems such as those of Cronquist and Takhtajan. Eventually, Flacourtiaceae, including this taxon, were reclassified into Salicaceae, a placement adopted by the APG III system and subsequently recognized by Plants of the World Online, though this classification remains disputed.^[19][20][21]

Xylosma tweediana goes by several common names within its range, where it is known by espina colorada and espina corona in Spanish and sucará in Portuguese.^[5][9]

The genus name Xylosma derives from xylon (Ancient Greek: ξύλον), meaning 'wood' or 'tree', and osmé (Ancient Greek: ὀσμή), meaning 'smell', overall referring to the aromatic wood found in some species.^[22] The species epithet, tweediana, is in honor of John Tweedie, who was stated to have observed the species in the original literature.^[10]

Xylosma tweediana is broadly distributed with a substantial population size. It currently faces no major threats, and projections suggest no future significant risks. As a result, it has been classified as Least Concern by the IUCN Red List, although many aspects of the assessment need expansion.^[1]

• Media related to Xylosma tweediana at Wikimedia Commons