Trzy linie rozwojowe
An analysis of two chloroplast DNA regions, published in 2019, distinguished three main groups. The first joined T. bonnieae, T. molinensis and T. recurvatus with the pair T. nigrispinus–T. verschaffeltii. The second consisted of T. aulacothele (T. weberi in the paper). The third included T. articulatus, T. alexanderi and T. aoracanthus, among others. [Las Peñas et al. 2019] [2-WWW]
The genus thus includes plants formerly described in Puna, Maihueniopsis, Cumulopuntia and Austrocylindropuntia. Similarity of segments alone may result from adaptation to similar conditions. The study compared them with fruit, seed-covering, root and leaf traits and with chromosome numbers. [Las Peñas et al. 2019]
Stems, fruit and seeds
The plants form separate segments whose connections differ in strength. In some species, a segment detaches easily and can give rise to a new plant. In others, the connection remains strong and branched clumps grow without frequent breakage. Geophytic species store a substantial share of their biomass underground in thickened roots. [Las Peñas et al. 2019] [Almirón et al. 2016] [Almirón et al. 2019]
Dry, dehiscent fruit and seeds in a corky covering characterise much of the genus. In T. nigrispinus, T. verschaffeltii and T. recurvatus, fruit is fleshy and remains closed. In these plants, the structure of the tissue surrounding the seed also differs from the typical corky arrangement. [Las Peñas et al. 2019]
Chromosomes and clonal propagation
The basic chromosome number is x = 11. Alongside diploids with 2n = 22 are plants with greatly multiplied complements. In material identified as T. aoracanthus, 242 chromosomes were counted, and in plants described as T. paediophilus, now merged with this species, 319 were counted. The results concern particular specimens and former taxonomic units. [Las Peñas et al. 2019] [2-WWW]
In T. aoracanthus, the strength of segment connections and transport of detached fragments by rainwater were studied. Breakage of the connection allows a propagule to detach, and its subsequent movement depends on surface topography, later rainfall and interception by vegetation. [Almirón et al. 2016] [Almirón et al. 2019]
Names in collections and publications
The current name T. aulacothele includes plants known from most earlier papers as T. weberi. The subspecies T. aulacothele subsp. deminutus corresponds to the previously studied variety T. weberi var. deminutus. POWO retains T. abditus as a separate species. Each taxon profile gives the name used in the cited paper. [2-WWW] [Las Peñas et al. 2019] [Kiesling et al. 2023]