Identification and circumscription of the name
The species usually has a solitary, spherical or flattened stem. The historical description distinguishes 15–23 ribs, most often 21, and large areoles. One of the stronger central spines is distinctly flattened and hooked at the tip. Flowers are pink to purple. Seeds were described as kidney-shaped, around 1.5 mm long, with small surface depressions. [Britton and Rose 1922, p. 143]
In POWO, the species includes three subspecies, F. latispinus subsp. latispinus, subsp. greenwoodii and subsp. spiralis. The former combinations Echinocactus latispinus and Ferocactus recurvus var. latispinus are synonyms. The subspecies provides an important refinement of identification. In the microbiome study, the authors gave the species name without a subspecies rank, so the results remain assigned to their material. [2-WWW] [Mascot-Gómez et al. 2021]
Distribution and flowering
According to POWO, the natural range extends across Mexico from Durango to Puebla and includes deserts and dry scrub. Material for the seed study was collected from a population in the municipality of Guadalcázar, San Luis Potosí, during the rainy season in 2018. Mature, completely closed fruits were collected. This collection method allowed seeds to be studied before contact with the soil surface. [2-WWW] [Mascot-Gómez et al. 2021]
The RHS describes a stem reaching around 25 cm in diameter in cultivation and winter flowering. Britton and Rose recorded one specimen in a New York garden flowering in November 1913, with the same flower opening on four successive days. This is an observation of a specific cultivated plant, useful alongside the seasonal horticultural description. [1-WWW] [Britton and Rose 1922, p. 143]
Seed bacteria and the limits of their identification
Mascot-Gómez and colleagues separated microorganisms on the seed surface from those in internal tissues. Fruits came from at least ten plants of each species studied. After extraction, however, seeds were pooled into one sample per species. For F. latispinus, bacterial 16S rRNA gene reads indicated a predominance of Stenotrophomonas on the surface and Kluyvera inside. These are relative proportions of marker sequences, describing the composition of this sample. [Mascot-Gómez et al. 2021, p. 2, 4–5]
Thirteen bacterial isolates were cultured from the seeds. Among surface isolates of Enterobacter were strains with marked chitin-degrading activity and acetylene reduction in an assay detecting nitrogenase activity. The first trait may matter in interactions with fungi, while the second indicates potential for nitrogen fixation. Both were measured under laboratory culture conditions. The amount of nitrogen transferred to seedlings of this species was not determined. [Mascot-Gómez et al. 2021, pp. 4]
Under the laboratory conditions used, no fungi were cultured from F. latispinus seeds, although DNA analysis detected their sequences. Culture and marker analysis therefore reveal different parts of the microbial community. The experiment reinoculating seeds was conducted on Echinocactus platyacanthus. Its germination and fungal colonisation results were not tested in an analogous way in F. latispinus. Details of the methods are presented in the article on the seed microbiome. [Mascot-Gómez et al. 2021, p. 4–5, 8–9]
Cultivation and propagation
The RHS recommends a sunny position and a free-draining cactus growing medium. Watering should be moderate during growth, while in winter the medium remains almost dry. In Polish conditions, this corresponds to growing in pots in a bright room or greenhouse with protection from freezing. The species was assigned class H2 in the British RHS scale, covering low temperatures above freezing. The class describes conditions for cultivation in Britain. It does not specify an experimental frost-damage threshold. [1-WWW]
The RHS gives spring sowing at 21°C as a propagation method. The horticultural profile also notes susceptibility to mealybugs and root and stem rots with excessive watering. Identification of these problems is explored in separate texts in the diseases and pests section. [1-WWW]
Related articles
Materials from the author's archive
The species also appears in Konrad Szychowski's private material archive. [Cactáceas y Suculentas Mexicanas 1959, file p. 18] [Kaktologia 2009b, file p. 9] [Neciu b.d., file p. 1] [Romulski b.d., file p. 7]
Synonyms and names in the literature
Cactus latispinus · Echinocactus latispinus · Ferocactus recurvus var. latispinus · Bisnaga latispina · Bisnaga recurva subsp. latispina · Mammillaria latispina · Melocactus latispinus [2-WWW]