Stem segments, roots and fruits
Stems consist of globular, ovoid or elongated segments. Young growth may have small leaves that dry early. Areoles contain glochids, while spines vary in length, stiffness and arrangement. The mature fruit has a dry chamber with seeds covered by tissue of funicular origin. The shape of this covering and its thickenings matters in taxonomic comparisons. [Pauca-Tanco and Quipuscoa 2020] [Hoxey et al. 2023a]
A compact cushion habit often accompanies a thick storage root, while looser forms have fibrous roots. In the regional Arequipa compilation, C. zehnderi is a clear exception. It forms cushions but has fibrous roots. Soft-spined C. mollispina also combines compact growth with this root system. [Pauca-Tanco and Quipuscoa 2020] [Hoxey et al. 2023a]
Two levels of description. Population and species
The 2020 Arequipa revision recognized twelve species. POWO now treats some of them more broadly. C. mistiensis is a synonym of C. corotilla, while the names C. crassicylindrica, C. ignota, C. multiareolata and C. tumida are included in C. sphaerica. Their field descriptions retain value as documentation of particular populations and narrower taxonomic treatments. [Pauca-Tanco and Quipuscoa 2020] [2-WWW]
Habitat variation
In the Arequipa region, C. leucophaea was described from coastal lomas at 30–1058 m elevation, and C. ignescens from high-Andean habitats at 3300–4700 m. C. mollispina grows in the Río Yauca valley at 1700–1800 m. This range of habitat conditions requires relating observations to species and place of origin. [Pauca-Tanco and Quipuscoa 2020] [Hoxey et al. 2023a]
Flowering and recruitment
In many described populations, flowering occurred during part of the local dry season. Flowers were visited by hymenopterans, beetles and butterflies, and in individual accounts also hummingbirds. Detailed tests of pollen-transfer effectiveness were not the revision's purpose. The 2024 sowing of C. ignescens indicates the significance of light access after mechanical seed preparation. [Jara-Peña et al. 2024] [Pauca-Tanco and Quipuscoa 2020]