Name and discovery
Plants of the World Online accepts Lophophora alberto-vojtechii as a separate species. The name was published in Cactus & Co. in 2008. Šnicer, Bohata and Myšák described its discovery during an expedition in February 2007. Initially, the tiny plants were considered possible seedlings of L. williamsii. Observations of flowering and further specimens revealed persistent features of the miniature taxon. The epithet commemorates Albert Vojtěch Frič and Vojtěch Myšák. [2-WWW] [Šnicer et al. 2009, Šnicer et al., pp. 295, 298]
The stem above and below ground
The crown is flat or slightly convex, greyish green, sometimes with a violet tint. The expanded 2009 description gives adult stem widths of 10–50 mm, with a mean of 18 mm. Specimens exceeding 25 mm were exceptional. Usually five weakly marked ribs occur, occasionally eight. Fine hairs appear near the tip but fall off early. The areoles consequently become inconspicuous. [Šnicer et al. 2009, p. 296–298]
Most of the plant remains underground. The cylindrical underground stem section was described as extending around 25 mm below the crown and lengthening with age. It passes into a thick, tuberous root up to 30 mm long, typically 16 mm in diameter at its connection with the stem. The root is smooth, off-white to creamy yellow. Remains of former areoles accumulate on the older underground stem portion. They mark the growth of a plant whose above-ground crown still remains very small. [Šnicer et al. 2009, p. 297–298, 300]
Flowering at a small diameter
The authors observed flowering at a stem diameter of around 10 mm. Several flowers could develop in one flush. The open flower is 15–35 mm in diameter, averaging 23 mm, and can obscure the whole crown. Tepals are white to dull pink, less often creamy yellow, with a darker stripe along the centre. Their tips may be broadly rounded. Stamen filaments are white, anthers yellow-orange, and the white style projects above the anthers. [Šnicer et al. 2009, p. 296–298]
Insects visiting flowers were seen in the field, including two bees of different sizes and a fly. The publication establishes neither their species nor the effectiveness of a single visit in pollen transfer. Flower similarity and a shared flowering period with the associated Mammillaria coahuilensis led the authors to hypothesise shared pollinators. The visits and similarity in floral features remain directly documented. [Šnicer et al. 2009, p. 298]
Fruit and seed microsculpture
The fruit is spherical to slightly club-shaped, pale, off-white, yellowish or pinkish. It dries over time. Black seeds are 1.15–1.45 mm long and 1.0–1.45 mm wide. The hilum, the attachment scar, is broad and compressed into a V shape, with a distinct rim. The coat has convex cells with clearly marked boundaries. Electron micrographs show this structure in material from several regions. [Šnicer et al. 2009, p. 298–299]
Plants described as L. koehresii (now a synonym of L. diffusa in POWO) had a more open, almost circular hilum and reticulate seed-coat surface in the authors' comparison. Habitat and flower similarity between the two groups therefore did not extend to the full set of seed features. This comparison of material identified by the authors is retained after adoption of current names. [Šnicer et al. 2009, pp. 296, 299] [2-WWW]
Plains and seasonal withdrawal
The type locality in northern San Luis Potosí lies at 1700 m elevation. The authors described flat alluvial deposits that turned into muddy surfaces after rain. During prolonged drying, plants contracted and withdrew into small depressions. Wind deposited dust and dry leaf remains. When rain returned, the hydrated crown swelled and rose above the surface again. This is an observation of seasonal crown-position changes, without an anatomical measurement of root force. [Šnicer et al. 2009, p. 297–298]
POWO restricts the accepted range to San Luis Potosí. The 2009 article also lists populations discovered by the authors in Zacatecas, Coahuila and Nuevo León. This is a broader scope of field reports than the range accepted in the database. The article's account of flowering on a day with a morning temperature of −3°C establishes neither a frost-hardiness threshold nor an overwintering temperature. Exposure duration, tissue temperature and assessment of later damage are absent. [2-WWW] [Šnicer et al. 2009, p. 300]