Maihueniopsis Speg.
Creators: name: Walter, Helmut E.
name: Guerrero, Pablo C.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Caryophyllales
Cactaceae
Maihueniopsis

description: Maihueniopsis Speg.:    
 — Hunt’s et al. (2016) and Hunt’s (2013) circumscription of the genus Maihueniopsis includes only four species occurring in Chile, i.e. the two endemics M. archiconoidea F.Ritter and M. conoidea F.Ritter, and two species occurring also in Argentina (M. darwinii Hnsl. and M. ovata Pfeiff.). These authors merged the rest of the Chilean species described by Ritter (1980) and Espinosa (1933) into the widespread Argentinean species M. glomerata (Haw.) R.Kiesling without any evidence (i.e. detailed descriptions, morphological keys, and/or molecular phylogenies). They did not realize, however, that the Chilean Maihueniopsis are clearly divided into two main groups (the “ glomerata - group” and the “ domeykoensis- group”) when all members of the domeykoensis group [M. camachoi (Espinosa) F.Ritter, M. colorea F.Ritter, M. crassispina F.Ritter, M. domeykoensis F.Ritter, M. grandiflora F.Ritter, and M. wagenknechtii F.Ritter] are included in the sampling. All members of the domeykoensis group are endemic to the western slopes of the Chilean Andes. Populations of M. glomerata s.str. had not yet been documented in Chile. The molecular-based phylogeny presented by Ritz et al. (2012) shows that M. domeykoensis [a species that was lumped into M. glomerata by Hunt (2011)] is sister to the rest of the nine taxa (all of them being members of the glomerata group). Ritz et al. (2012) found it “interesting” that M. domeykoensis was not placed within the “ glomerata ” group. Their sampling was unbalanced, as they included nine species assigned to the “ glomerata ” group (see above) but only one assigned to the “ domeykoensis ” group (i.e. M. domeykoensis).   
 Maihueniopsis domeykoensis is likely a separate lineage. So, we conclude that a) as M. domeykoensis did not cluster with M. glomerata (or other members of the glomerata -clade), it cannot be considered a synonym of M. glomerata, and thus b) the rest of the members of the domeykoensis group, who share the same morphological characters with M. domeykoensis, cannot be considered synonyms of M. glomerata. This conclusion is corroborated by a broadly sampled (i.e. all the members of the domeykoensis group) molecular phylogeny (Guerrero, in preparation) that showed that Maihueniopsis is split into two groups congruent with the above presented morphylogy-based groups (a morphologybased key is reported below). According to the results of the phylogenetic analyses one large species-complex was split: Maihueniopsis glomerata. However, Hunt (2016) withdrew his opinion and reinstalled all of the formerly not accepted species of the domeykoensis-clade.   
 A nomenclatural note on the no validly published name “ Maihueniopsis leoncito (Werderm.) F.Ritter ” is necessary. According to Art. 41.5 ICN (Turland et al. 2018), Ritter’s “ Maihueniopsis leoncito ” is invalid because it does not include the place of publication of the basyonym. The correct name Maihueniopsis leoncito (Werdermann ex F.Ritter) P.C. Guerrero & Helmut Walter was recently published by Guerrero & Helmut Walter (2019);   
 1. Branch segments ≤ 5 cm; spines ± flattened; mature fruits unspined, ±ovoid or cylindric; seeds pale yellow, with short trichomes (“ glomerata -group”)...........................................................................................................................................................................2   
 - Branch segments 5–10 cm, spines terete in cross-section; fruits spiny, obconical urn-shaped; seeds brown, with long trichomes (“ domeykoensis -group”).....................................................................................................................................................................7   
2. Spines strongly flattened and broad at base, often deflexed..............................................................................................................3  
- Spines less flattened, not broad at base, thinner, not deflexed...........................................................................................................4  
 3. Compact, large cushions 20–60 cm high; segments to 4 cm, broadly conical, apex acute; spines to 4 cm, pointed downwards to porrect.........................................................................................................................................................................  10. M. leoncito    
 - Small, loose cushions up to 20 cm diam. and 10 cm high; segments <2.5 cm, conoid to globose, apex obtuse; spines ≤ 2 cm, deflexed or appressed to segment........................................................................................................................  1. M. archiconoidea    
4. Branch segments <5 cm; spines 3-4 cm.............................................................................................................................................5  
- Branch segments 1.5–3 cm; spines <3cm...........................................................................................................................................6  
 5. Shrubs forming compact cushions up to 50 cm wide and 35 cm high; areoles numerous, 4-5 mm, upper 2/3 spiniferous; stigmalobes green.................................................................................................................................................................... 7. M. darwinii   
 - Cushions loose, to 10 cm high; areoles few, 1–2 mm, only upper third to upper half spiniferous; stigma-lobes red..................................................................................................................................................................................................................  11. M. ovata    
 6. Small, loose cushions; spines directed sideward to ±downwards, new ones blackish-violet; fruits cylindric, areoles wooly................................................................................................................................................................................................ 5. M. conoidea   
 - Large compact cushions; spines porrect to erect, new ones yellowish; fruits ovoid, areoles not woolly.............  2. M. atacamensis    
7. Areole number <40, only upper 2/3 of areoles spiniferous; spineslong, 5–12 cm............................................................................8  
 - Areole number 40-60, even basalmost ones spiniferous, spines 2–3 cm......................................................... 12. M. wagenknechtii   
8. Spines red-brown, base whitish; seeds small.....................................................................................................................................9  
- Spines white or light honey-brown; seeds large...............................................................................................................................10  
 9. Stigma lobes red; spines to 12 cm.............................................................................................................................. 3. M. camachoi   
 - Stigma lobes green; spines to 6 cm................................................................................................................................ 4. M. colorea   
 10. Shrubs up to 2 m diam.; spines white, those on flowers and fruits contorted........................................................ 9. M. grandiflora   
- Shrubs to 50 cm diam.; spines honey-brown, stiff...........................................................................................................................11  
 11. Segments light yellowish-green; most spines directed upwards; stigma green.................................................. 8. M. domeykoensis   
 - Segments bluish grey-green; most spines directed; sideward or downwards; stigma ruby-red............................... 6. M. crassispina
description: 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 86-87, DOI: 10.11646/phytotaxa.550.2.1, http://zenodo.org/record/6641038