Leucostele is a genus of large columnar cacti in the family Cactaceae, order Caryophyllales, native to the arid and semi-arid regions of Argentina, Bolivia, and Chile. The genus comprises around eight accepted species, all characterised by tall, ribbed, columnar stems that can reach several metres in height, densely armed with spines arranged along pronounced ribs.
Species of Leucostele were long classified within the broadly circumscribed genus Echinopsis (and before that under Trichocereus), but are now recognised as a distinct genus by Plants of the World Online. The genus was formally separated following molecular phylogenetic studies published around 2012; the type combination Leucostele terscheckii bears the authorship (Pfeiff.) Schlumpb., 2012.
Among the best-known members is Leucostele terscheckii, a massive columnar cactus of the Argentine dry forests and scrublands of the Chaco region, and Leucostele atacamensis, which grows at high altitudes in the Atacama and Andean zones of Chile and Bolivia. Leucostele chiloensis occurs further south along the Chilean coast. These cacti occupy rocky hillsides, desert grasslands, and shrublands on sandy or gravelly soils, often forming a prominent element of the landscape.
Distribution
Leucostele is native to western South America, with species distributed across Argentina, Bolivia, and Chile. Individual species span a wide range of elevations and habitats, from coastal Chilean shrublands (L. chiloensis, L. litoralis) to high-altitude Andean slopes (L. atacamensis) and the dry Chaco forests of north-western Argentina (L. terscheckii).
Taxonomy Notes
Leucostele species were historically included within Trichocereus and later within a broadly circumscribed Echinopsis. Plants of the World Online now treats Leucostele as an accepted genus in Cactaceae; the reclassification was formalised around 2012 (Schlumpberger), with the type species combination Leucostele terscheckii (Pfeiff.) Schlumpb. GBIF records the genus under order Caryophyllales with eight accepted descendants and taxonomic status ACCEPTED.
Ecology
Leucostele cacti occupy arid to semi-arid environments: desert grasslands, rocky shrublands, and hillsides with sandy or gravelly soils. They are adapted to strong solar radiation, low rainfall, and wide diurnal temperature variation typical of Andean foothills and Pacific-facing slopes of South America.
