Structure and relationships
Cylindrical stem segments, areoles with glochids and leaves present at least on young growth form a characteristic set of features of the genus. In A. subulata, leaves are long and persistent, while in A. cylindrica they are much shorter and fall quickly. A. pachypus is distinguished by prominent diamond-shaped tubercles and A. floccosa by a mat-forming habit. Differences thus cover both overall form and the contribution of individual organs to carbon balance. [Ozerova and Timonin 2020b] [Taquiri-Yanqui et al. 2024] [Sakhraoui et al. 2022] [Jara-Peña et al. 2024]
Phylogenomic analyses place the genus in the South American Tephrocacteae lineage. The 2023 reconstruction indicates that long-lived photosynthetic leaves became established independently in different opuntioid lineages. Today's leafy species represent their own evolutionary histories. Their characters are interpreted on the relationship tree. [Majure et al. 2023]
The leaf and stem share the work
In A. subulata, well-hydrated leaves take up most CO₂ during the day, while the green stem shows nocturnal uptake. During drought, the nocturnal share of leaf assimilation increases and total daily carbon uptake decreases. The outer and inner leaf parenchyma contain chloroplasts and water. This organization combines assimilation and storage functions. [Nobel and Hartsock 1987] [Martin and Wallace 2000] [Ozerova and Timonin 2020b]
Natural range and feral populations
Distribution descriptions should include native sites and sites resulting from introduction separately. For example, A. pachypus is endemic to Peru, while A. subulata and A. cylindrica were also studied in feral populations in Algeria. Their behaviour differed. The first species formed numerous expanding populations, while the second maintained small, slow-growing clusters. [Taquiri-Yanqui et al. 2024] [Sakhraoui et al. 2022]
Reproduction in studies
Vegetative propagation can involve detached stem segments, and rooting of fallen fruits has also been described in A. pachypus. In an experiment with A. floccosa seeds, mechanical scarification was used, followed by germination in both light and darkness. Results for these three species present separate mechanisms of regeneration. [Taquiri-Yanqui et al. 2024] [Sakhraoui et al. 2022] [Jara-Peña et al. 2024]