The relevance of classifying the Cactaceae family into different subfamilies helps to better understand the subdivision into clades that differ morphologically (see key below). On the other hand, the delimitation of some subfamilies has shown to been difficult (for example the paraphyly of the Pereskioideae K.Schum. and the ambiguous relationships of the Maihuenioideae P.Fearn with other subfamilies). Also, the tribes within the Opuntioideae K.Schum. and Cactoideae Eaton have undergone several changes, as molecular-based phylogenies provided new information about evolutionary relationships of its members. Most of the proposed changes at these taxonomic levels have an impact on the classification of Chilean cacti because the cactus flora in the Atacama Desert, the Altiplano, the Mediterranean area, and the Chilean Patagonian steppe harbours three of the four subfamilies and seven of the ten tribes. 1. Stems with functional leaves, at least on immature shoots; a 739 bp non-coding intron region in the chloroplast-encoded gene rpo C1 present.....................................................................................................................................................................................2 - Stems without functional leaves; a 739 bp non-coding intron region in the chloroplast-encoded gene rpo C1 is lost (subfam. Cactoideae).........................................................................................................................................................................................3 - Stems without functional leaves; a 739 bp non-coding intron region in the chloroplast-encoded gene rpo C1 is lost (Subfamily CACTOIDEAE)................................................................................................................................................................................10 2. Leaves persistent, terete; glochids on areoles absent; seeds without funicular envelope; stems astomatous, barky... (subfam. Maihuenioideae).......................................................................................................................................................... 12. Maihuenia - Leaves ephemeral, flat; areoles with spines and glochids; seeds encased in a funicular envelope; stems stomatous, bark formation delayed (subfam. Opuntioideae).........................................................................................................................................................4 4. Branch segments flat to subterete; shrubs to 20 cm high.................................................................................................... 22. Tunilla - Segments cylindric; shrubs to 1.5 m high........................................................................................................... 14. Miqueliopuntia 3. Branches flattened to subterete or cylindric.........................................................................................................Tribe OPUNTIEAE - Branch segments never flattened, terete in cross-section...................................................................................................................5 5. Shrubs to 60 cm high, then mound-forming; segments to 10 cm, with determinate growth; spines without sheath..................................................................................................................................................................................... TEPHROCACTEAE (pro parte) - Shrubs to 1.5 m; branch segments to 30 cm, with indeterminate growth; spines with a papery sheath (CYLINDROPUNTIEAE)................................................................................................................................................................................. 6. Cylindropuntia 6. Flowers dark red; petaloids few, 10; fruits 2–5 cm, greenish yellow, not glabrous, pulp never red.................................................7 7. Seeds laterally compressed; perisperm large......................................................................................................................................8 - Seeds ± globose; perisperm small......................................................................................................................................................9 8. Flowers immersed into apex; funicular girdle of seed formed into a papery wing.................................................... 17. Pterocactus - Flowers not immersed; seeds not winged.............................................................................................................. 13. Maihueniopsis 9. Segments ±globose, etuberculate, easily detaching; spines on segments and fruits 0.5 m, branches columnar or thickly cylindric....................................................................................................................21 - Plants <50(-70) cm, globose, elongating with age................................................................................................. 11. Lobivia [ferox] 21. Plants ±branching, shrubby or treelike; flowers narrowly funnelform, whitish........................................................... 10. Leucostele - Plants usually unbranched, thickly cylindric; flowers campanulate, yellow............................................................... 19. Soehrensia The comparison of the taxonomic classifications shows that there are important differences in the number of Chilean genera and species (Table 1). Hunt’s classification (2006, 2013, 2016) includes the lowest number of species (95), whereas Rodríguez et al. (2018) reports the lowest number of genera (17). The percentage of endemic species also varies: 73% by Hunt et al. (2006, 2013, 2016), 74% by Rodríguez et al. (2018), 81% in the present study. These results highlight the importance of updating the taxonomic classifications in the Flora of Chile, because underestimating the endemism and number of species may have major negative effects on conservation (see e.g., Mace 2004, Duarte et al. 2014). The number of species accepted here means that the Cactaceae represent 6% of the Chilean native angiosperms and 5% of endemic species of Chile (Rodríguez et al. 2018).

Published as part of Walter, Helmut E. & Guerrero, Pablo C., 2022, Towards a unified taxonomic catalogue for the Chilean cacti: assembling molecular systematics and classical taxonomy, pp. 79-98 in Phytotaxa 550 (2) on pages 80-81, DOI: 10.11646/phytotaxa.550.2.1, http://zenodo.org/record/6641038