Endemiczny rodzaj Galápagos
Plants of the World Online recognises Brachycereus nesioticus as the only species in the genus Brachycereus. Its earlier name is Cereus nesioticus. In a section of Robinson's 1902 floristic account, Karl Schumann's description was published under Cereus. The current combination is attributed to Curt Backeberg and a publication from 1936. [2-WWW] [Robinson 1902] [2-WWW]
A clump of short, spiny stems
The stems are cylindrical and grow close together, forming compact clumps. Stöcklin describes their height as up to about 0.5 m and their spination as dense and yellowish brown. Schumann's original diagnosis emphasised stems spreading from a shared base. The low ribs were strongly crenate, dividing their course into tubercle-like sections. [Stöcklin 2009] [Robinson 1902]
Areoles, short shoots producing structures including spines, were described as round and sparsely woolly. The numerous spines varied in length, and their arrangement showed no clear division into central and radial spines. Schumann noted such a dense spine covering that the stem surface became invisible. These are features of the material documenting the original species description. [Robinson 1902]
Flower, fruit and seeds in the original description
The narrow floral tube bears areoles with spines, as does the exterior of the flower's lower region surrounding the ovary. The tepals are narrow, especially the inner ones. In the material Schumann described, the flower was 7 cm long. Stamen filaments were very short, less than 1 mm, and attached near the tube opening. [Robinson 1902]
The fruit was described as ellipsoidal, narrowed at the base, with spiny areoles in its upper part. The material studied was reported as around 2.5 cm long and 1.3 cm thick. It contained numerous ellipsoidal, reddish-brown seeds with a finely dotted surface. These measurements come from the species diagnosis. Their scope covers its material, rather than comparative measurements of all present-day populations. [Robinson 1902]
Islands and fissures in solidified lava
The Charles Darwin Foundation checklist confirms occurrence on Isabela, Fernandina, Pinta, Santiago and Genovesa, and on four islets. The species is endemic to the archipelago and remains widely distributed on relatively young lava fields. Stöcklin presents it as a pioneer plant on exposed lava. [24-WWW] [Stöcklin 2009]
Documentation of this habitat extends back to the original description. Lava fields were noted for specimens from Elizabeth Bay on Isabela, and bare black lava for collections from eastern Fernandina. The names Albemarle and Narborough used in that publication correspond to present-day Isabela and Fernandina. Lüttge describes plants occupying narrow lava fissures and fully exposed to the sun. [Robinson 1902] [24-WWW] [Lüttge 2010]
Crystals inside the tissues
In 2007, Hartl and colleagues studied calcium oxalate crystals in a broad sample of cacti. They combined X-ray diffraction with light, polarising and scanning electron microscopy. Material of B. nesioticus contained calcium oxalate in its dihydrate form, designated COD. The microscopic description includes single tetragonal bipyramids and druses made up of prismatic crystals. [Hartl et al. 2007]
A bipyramid takes the form of two pyramids joined at their bases. A druse is a cluster of multiple crystals. The study therefore documents both the mineral composition and several spatial crystal forms in this species. The authors considered the biological functions of such deposits more broadly as hypotheses. For B. nesioticus, they did not present an experiment resolving their role in radiation protection or regulation of calcium balance. [Hartl et al. 2007]
Fizjologia a rozpoznanie siedliska
Lüttge included B. nesioticus in a review of CAM plant ecology, discussing strongly sunlit lava surfaces. In 2010, he noted that he knew of no ecophysiological studies of this species. The habitat description and general knowledge of CAM provide a basis for hypotheses about water conservation. The detailed daily course of gas exchange in Brachycereus requires species-specific measurements. The relationship between these levels of knowledge is explored in “A cactus on solidified lava”. [Lüttge 2010]
Related articles
Synonyms and names in the literature
Cereus nesioticus [2-WWW]