Xylosma tweediana

Xylosma tweediana is a ramified shrub or tree, ranging from in height, typically featuring a globose crown when mature. It commonly bears stout, simple spines on its main branches that may reach up to , 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 . 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 long and wide. Leaf apices are broadly subacuminate or obtuse, and the bases taper attenuately into slender, flexuous petioles, which are initially puberulent, and measure . 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 , 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 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 in diameter, containing 2–5 angular-ovoid seeds up to long. Though herbarium specimens suggest sexual dimorphism in armature, with unarmed male branches and spiny female ones, this feature is not uniformly expressed. ==Distribution==

Xylosma tweediana is native to 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. ==Ecology==

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 . 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. ==Taxonomy==

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. The collective number of synonyms across different sources is approximately 18. Etymology 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. The species epithet, tweediana, is in honor of John Tweedie, who was stated to have observed the species in the original literature. ==Conservation status==

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. ==Notes==