Accepted species and name history
POWO accepts three species of Kadenicarpus, K. heliae, K. horripilus and K. pseudomacrochele. The genus occurs naturally in eastern Mexico. In the atlas, the former names Turbinicarpus horripilus, T. pseudomacrochele and T. heliae lead to the current genus. The name Bravocactus remains its synonym. [2-WWW]
The 2019 analysis included K. horripilus and the K. pseudomacrochele complex. The authors united the group formerly distinguished as Bravocactus with Kadenicarpus, retaining the latter name. Present-day K. heliae (formerly Turbinicarpus heliae) received its current combination in 2021. The modern genus therefore has a broader scope than the species actually examined in the 2019 study. [Vázquez-Sánchez et al. 2019, Vázquez-Sánchez et al., pp. 414–416] [2-WWW]
Relationships and seeds
In the 2019 analysis of DNA and structural traits, the Kadenicarpus studied formed a sister lineage to the Ariocarpus and Turbinicarpus group. Similar spherical stems and varied spines had previously led these plants to be grouped with other genera. A combination of seed and stem-tissue features supported their distinctness. [Vázquez-Sánchez et al. 2019, pp. 409, 412]
Seed-surface microsculpture in Kadenicarpus is smooth, and the micropyle and funicular scar form a shared region. Fruits open through longitudinal slits. These features co-occur with a particular tissue arrangement, although not all are exclusive to the genus. The authors assessed the group's shared origin from the full set of traits and DNA sequences. [Vázquez-Sánchez et al. 2019, p. 409, 412, 416–417]
Fibres and crystals in the stem
In the anatomical comparison of 35 taxa, xylem fibres in cortical bundles occurred only in the Kadenicarpus lineage studied. These bundles pass through storage parenchyma outside the main vascular cylinder. In contrast, the main stem xylem of the kadenicarpi studied was fibre-free, with vessels among wide-band tracheids. Fibre location is therefore an important part of the diagnostic feature. [De la Rosa-Tilapa et al. 2019, online version, pp. 2–4]
The hypodermis contained prismatic crystals, as in Turbinicarpus. In K. horripilus, prismatic crystals were also observed in the pith, while K. pseudomacrochele subsp. minimus had druses there. Cork cells of the secondary protective tissue had thin walls. Crystal distribution therefore differs between stem layers and between taxa within the same genus. [De la Rosa-Tilapa et al. 2019, online version, pp. 2–4]
Distribution and complex boundaries
The 2019 study described populations associated with limestone substrates in Hidalgo and Querétaro, including the Metztitlán canyon and Zimapán areas. The current POWO account gives a range from Querétaro to Veracruz for K. horripilus. The older publication's map represents the area and material analysed there, while the broader range of the currently accepted species requires use of the current database. [Vázquez-Sánchez et al. 2019, Vázquez-Sánchez et al., p. 415] [2-WWW]
The K. pseudomacrochele complex has three accepted subspecies in POWO. In the 2019 study, subspecies as circumscribed then did not form one clearly defined group on the tree. The authors indicated the need for broader population sampling. Current subspecies names organise the data, while the analytical result describes an unresolved biological question within the complex. [Vázquez-Sánchez et al. 2019, Vázquez-Sánchez et al., pp. 412, 414, 416] [2-WWW]
Biomineral sizes in a broad Cacteae comparison
In the 2022 study, Kadenicarpus was among groups with the smallest measured biominerals. Mean maximum length was around 32 µm in the cortex and 31 µm in the pith. For measurements, 25 biominerals were selected from each individual and layer in the middle part of the stem. Genus means refer to the material tested and do not describe each of the three current species separately. [De la Rosa-Tilapa et al. 2022, p. 2, 4, 8–9, tabela 1, ryc. 3]
The hypodermis of the kadenicarpi studied contained prismatic forms, as in Turbinicarpus. Their shape was compared with the druses of Rapicactus. The difference was a supporting taxonomic feature, and the chemical comparison used electron microscopy and energy-dispersive X-ray spectroscopy. [De la Rosa-Tilapa et al. 2022, pp. 5–9, Fig. 7]
Related articles
Synonyms and names in the literature
Bravocactus [2-WWW]