This is a revised version of an article that originally appeared in the December 2002 issue of The Baltimore Areole, newsletter of The Cactus & Succulent Society of Maryland. Anyone interested in more information on the club should see our website at http://www.cactus-mall.com/clubs/maryland.html.
THE RESURECTION OF OPUNTIOID GENERA
The species of sufamily Opuntioideae in the Cactaceae are easily recognized for having stems with true leaves that are often small and deciduous, relatively large seeds with a tan to brownish woody or corky covering and, most of all, areoles that bear glochids. Many of the species have flattened pad-like stems but just as many have cylindrical stems, often with raised podaria.
As much confusion as there has been over the accepted genera in the Cactaceae, the group surrounding the genus Opuntia Miller, subfamily Opuntioideae K.Schumann, has gone mostly untouched. Although it has long been clear that the treatment of the genus by Britton & Rose (1919) left the genus Opuntia extremely polymorphic and somewhat overlapping with the few genera they separated from it, no clearly defined generic concept had been proposed until recently.
Curt Backeberg (1958, 1977) and Franz Ritter had carried the splitting of genera begun by Britton & Rose to its extreme but their efforts did not make generic concepts any clearer.
Gordon Rowley (1958) had swung the pendulum in the opposite direction by lumping most of the genera recognized by Britton & Rose and Backeberg back into Opuntia. Lyman Benson (1982) employed a very broad concept of Opuntia in his book on the North American Cactaceae. Although their concept has had much popular support, there has been much more evidence gathered over the years to support separating a number of smaller genera from Opuntia in the broad sense.
In a two long overlooked papers, Harold Robinson (1973, 1974) had found evidence to support the recognition of Cylindropuntia and Grusonia as separate genera from Opuntia on the basis of spine and glochid morphology.
Roberto Kiesling (1984) had proposed reinstating several segregate genera for the South American Opuntioideae based on his detailed study of the plants. At first his concept was rejected by the IOS Cactaceae working party (Hunt & Taylor (1986, 1990), Barthelott & Hunt (1993)) but recently they have made a complete about face by accepting his generic concept and expending upon it with the support of studies in DNA, seed, pollen and spine morphology (see Anderson (2001), Hunt & Taylor (2002)).
Currently there are 15 recognized Opuntioid genera but further research may result in more.
The genus Opuntia Miller as now defined consists only of those species with articulated stems that are usually flattened and pad-like ("Platyopuntia"). The genus still includes the well-known "Prickly Pears", so common in the New World deserts. The genus is most unique for its pollen having a raised net-like (reticulate) pattern on its surface. Most of the species have fleshy berry-like fruit but some of the North American species have fruit that are dry and burr-like at maturity. The anomalous cylindrical stemmed species Opuntia chaffeyi Britton & Rose and O.salmiana Parmentier remain in Opuntia.
The genera Tacinga Br. & R. from the Caatinga region of eastern Brazil and Nopalea Salm-Dyck from the Caribbean, southern Florida, Mexico and Central America have similar stems but the pollen surface is smooth or spotted and the flowers are typically adapted to pollination by birds. The concept of Tacinga has been expanded to include the anomalous species formerly in the series Inamoenae Br. & R. and Palmadorae Br. & R. of Opuntia. Opuntia quitensis Weber from Ecuador & Peru, Opuntia lilae Trujillo & Ponce from Venezuela and the Opuntia stenopetala Engelmann group (series Stenopetalae Br. & R.) from Mexico appear to also belong in Tacinga as the genus is defined by Taylor, Stuppy & Barthelott (2002).
The arborescent genera Consolea Lemaire and Brasiliopuntia (K.Schumann) A.Berger are unique for their dimorphic stems. The main stem is elongate and indeterminate while the lateral branches are pad-like and jointed.
The genus Tunilla Hunt & Iliff was named for the former "Airampoa group" (series Airampoae Backeberg) from the southern Andes and is unique among the pad-type genera by having fruit that split open when mature.
The monotypic genus Miqueliopuntia Fric from Chile superficially resembles Cylindropuntia but the stems are articulate with prominent narrow podaria and glaucous.
The genera Quiabentia Britton & Rose from South America and Pereskiopsis Britton & Rose from North America are unique for having fleshy stems and persistent broad and flattened fleshy leaves.
The North American "Chollas", Cylindropuntia (Engelmann) Knuth and Grusonia F.Reichenbach are shrubby to mat forming and are easily distinguished from all the other genera by having spines covered in a papery sheath.The genus Grusonia has been divided into four subgenera by Stuppy (2002) based on their seeds and vegetative form.
Pterocactus K.Schumann are dwarf geophytes easily recognized by its tuberous rootstock and dehiscent fruit with winged seeds.
Tephrocactus Lemaire was used as a catchall for all the South American globular to mat-forming species by Backeberg (1958, 1977) but is now restricted by Kiesling (1984) to be a small group of Argentine dwarf shrubby species with articulate stems and dehiscent fruit.
Maihueniopsis Spegazzini is now recognized to consist of Andean mat-forming species with fleshy indehiscent fruit. Stuppy (2002) includes Puna Kiesling in Maihueniopsis as a subgenus but these distinctive dwarf tuberous rooted species can just as well stand alone in their own genus.
The species of Cumulopuntia Ritter are indistinguishable from Maihueniopsis in their growth form but are distinguished by having thick walled fruit that are hollow inside.
The genus Austrocylindropuntia Backeberg is in some ways the South American counterpart to Cylindropuntia but the spines lack a papery sheath. The Austrocylindropuntia flocossa (Salm-Dyck) Ritter group consists of high altitude Andean species that form extensive mats of stems often completely covered in wool.
Austrocylindropuntia verschaffeltii (Cels) Backeberg, A.haematacantha Backeberg and Maihueniopsis nigrispina (K.Schumann) Kiesling (including Tephrocactus atroglobosus Backeberg) are anomalous and may merit a genus of their own.
Although not mentioned by Stuppy (2002), the genera Consolea and Nopalea are unique by having a distinctive cup-shaped base to the style.
List of accepted Opuntioid Genera
(based on Stuppy (2002))
Cactaceae subfamily Opuntioideae K.Schumann (1890)
Tribe Austrocylindropuntieae Wallace & Dickie (2002)
Austrocylindropuntia Backeberg (1938) (including Opuntia series Floccosae Britton & Rose (1919)) 12 sp. Argentina, Bolivia, Ecuador, Peru
Cumulopuntia Ritter (1980) (Tephrocactus sensu Backeberg, in part) 18 sp. Peru, Bolivia, Argentina, Chile
Tribe Pterocacteae Doweld (1999)
Pterocactus K.Schumann (1897) 8 sp. Argentina
Tribe Tephrocacteae Doweld (1999)
Tephrocactus Lemaire (1862) emended Kiesling (1984) not sensu Backeberg (including Ursopuntia Heath (1999)) 7 sp. Argentina
Maihueniopsis Spegazzini (1925) (Tephrocactus sensu Backeberg, in part) 13 sp. Peru, Bolivia, Argentina, Chile
Maihueniopsis subgen. Puna (Kiesling) Stuppy (2002) (Puna Kiesling (1982), Opuntia series Clavarioides Britton & Rose (1919)) 3 sp. Argentina, Bolivia
Tribe Cylindropuntieae Doweld (1999)
Quiabentia Britton & Rose (1923) 2 sp. Brazil, Paraguay, Bolivia, Argentina
Pereskiopsis Britton & Rose (1907) 8 sp. Mexico, Guatemala
Grusonia F.Reichenbach ex K.Schumann in Britton & Rose (1919) 17 sp. southwestern US, Mexico
Grusonia subgen. Corynopuntia (Knuth) Stuppy (2002) (Corynopuntia Knuth (1935))
Grusonia subgen. Micropuntia (Daston) Stuppy (2002) (Micropuntia Daston (1947))
Grusonia subgen. Marenopuntia (Backeberg) Stuppy (2002) (Marenopuntia Backeberg (1950))
Cylindropuntia (Engelmann) Knuth (1935) ca. 35 sp. southwestern US, Mexico, Caribbean
Tribe Opuntieae Salm-Dyck (1845)
Miqueliopuntia Fric ex Ritter (1980) 1 sp. Chile
Tunilla Hunt & Iliff (2000) (Opuntia series Airampoae Backeberg (1953), Airampoa Fric (1935) nom. nud.) 10 sp. Argentina, Bolivia, Chile, Peru
Brasiliopuntia (K.Schumann) A.Berger (1926) (Opuntia series Brasiliensis Britton & Rose (1919)) 2 sp. Brazil, Paraguay, Argentina, Bolivia, Peru
Consolea Lemaire (1862) (Opuntia series Spinossimae Britton & Rose (1919)) 9 sp. Caribbean, Florida.
Tacinga Britton & Rose (1919) (including Opuntia series Inamoenae Britton & Rose (1919), series Palmadorae Britton & Rose (1919), ?Opuntia series Stenopetalae Britton & Rose (1919)) ca. 6 sp. Brazil (probably also Mexico, Ecuador, Peru, Venezuela)
Nopalea Salm-Dyck (1850) 9 sp. Mexico to Panama, Caribbean
Opuntia Miller (1754) (including Plutonopuntia Heath (1999), Salmonopuntia Heath (1999)) ca. 150 sp. widespread in New World
Key to the Opuntioid genera
(modified from Stuppy (2002))
A. Cylindrical stemmed woody shrubs with persistent broad, flat leaves. (B.)
B. Stems articulated, branches pseudo-vertilillately arranged; flowers pink or red, usually terminal .Quiabentia Britton & Rose
BB. Stems not articulated, branches not vertilillately arranged; flowers yellow, usually lateral ..Pereskiopsis Britton & Rose
AA. Perennials to shrubs with awn-shaped to minute, mostly early caducous, leaves. (C.)
C. Spines lacking a papery sheath. (D.)
D. Plants without dimorphic stems. (E.)
E. Fruit indehiscent, fleshy or dry at maturity. (F.)
F. Pollen with perforate exine (surface not reticulate). (G.)
G. Stems cylindrical to clavate, often with distinct podaria; plants shrubby, mound foming, mat-forming or tuberous rooted geophytes. (H.)
H. Cylindrical stemmed shrubs or mound forming. (I.)
I. Stems indeterminate, not segmented, green, often with reticulate low podaria ..Austrocylindropuntia Backeberg
II. Stems determinate, segmented, glaucous, with prominent narrow podaria .Miqueliopuntia Fric ex Ritter (1980)
HH. Stems clavate, creeping or mat forming. (J.)
J. Mature fruit fleshy. (K.)
K. Areoles more or less evenly distributed on stem segments; mature fruit pulpy, not hollow; seeds woolly ..Maihueniopsis Spegazzini
KK. Areoles mostly concentrated toward apex of stem segments; mature fruit hollow; seeds smooth or rugose ... Cumulopuntia Ritter (1980)
JJ. Mature fruit dry; stems calvate to turbinate, tuberous rooted geophytes .Maihueniopsis subgenus Puna (Kiesling) Stuppy (2002) (Puna Kiesling (1982))
GG. Stems flattened, without podaria, or if cylindrical, stems scandent. (L.)
L. Flowers with tepals erect to strongly recurved at anthesis; style base slender ..Tacinga Britton & Rose
LL. Flowers almost completely closed during anthesis with only the style and staminal column exserted through a narrow opening between the tepals; style base cup-shaped Nopalea Salm-Dyck
FF. Pollen with reticulate exine (surface prominently reticulate); stems flattened or rarely cylindrical, podaria usually absent ....Opuntia Miller
CC. Fruit dehiscent at maturity. (M.)
M. Mature fruit fleshy, dehiscing by a single lateral slit; seeds not arillate or winged; plants mat forming, branches rounded or flattened .. Tunilla Hunt & Iliff (2000)
MM. Mature fruit dry; plants not mat forming. (N.)
N. Areoles deeply sunken; mature fruit irregularly dehiscent; seeds usually with a prominent corky aril, plants dwarf shrubs ..Tephrocactus Lemaire
NN. Areoles not deeply sunken; mature fruit capsular (pyxidium), dehiscent transversely in the lower third; seeds winged, plants tuberous rooted geophytes . Pterocactus K.Schumann
DD. Shrubs with dimorphic stems (main stem cylindrical and indeterminate; branches flattened and determinate.) (O.)
O. Flowers rotate, with a ring of hair-like staminodes between the tepals and stamens; style base sender .. .. .Brasiliopuntia (K.Schumann) A.Berger
OO. Flowers campanulate, staminodes absent; style base cup-shaped .Consolea Lemaire
CC. Spines with a papery sheath. (P.)
P. Spines sheathed only at apex; glochids with rounded base; stems clavate and mat forming or rarely subshrubby (Q.) .. ..Grusonia F.Reichenbach
Q. Plants trailing, mat-forming to thicket-forming; spines of fruit stiff; larger spines flattened, rigid, papillate and rough. (R.)
R. Stems cylindrical, strongly ribbed, to 2 m tall Grusonia subgenus Grusonia F.Reichenbach
RR. Stems clavate, strongly tuberculate, less than 6 dm tall .Grusonia subgenus Corynopuntia (Knuth) Stuppy (2002)
QQ.. Plants clump-forming or subshrubby; spines of fruit hair-like, flexible; spines acicular, flexible or reduced in size, not papillate or rough. (S.)
S. Stems clavate to cylindrical, to 15 cm tall, tubercles rounded on young stems or absent Grusonia subgenus Micropuntia (Daston) Stuppy (2002)
SS. Stems cylindrical to narrow clavate, to 6 dm tall, tubercles narrow on young stems ..Grusonia subgenus Marenopuntia (Backeberg) Stuppy (2002)
PP. Spines sheathed entire length; glochids with base flattened, fish-tail like; plants shrubby . Cylindropuntia (Engelmann) Knuth
Anderson, E.F. (2001) THE CACTUS FAMILY. Timber Press.
Backeberg, C. (1958) DIE CACTACEAE. Volume 1.
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Barthelott, W. & Hunt, D.R. (1993) CACTACEAE in Kubitzki, K. et al. (eds.) THE FAMILIES AND GENERA OF FLOWERING PLANTS 2: 161-197.
Benson, L. (1982) THE CACTI OF THE UNITED STATES AND CANADA. Stanford University Press.
Britton, N.L. & Rose, J.N. (1919) THE CACTACEAE, volume 1. Carnegie Institute of Washington.
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Iliff, J. (2002) THE ANDEAN OPUNTIAS: AN ANNOTATED CHECKLIST OF THE INDIGENOUS NON-PLATYOPUNTIOID OPUNTIAS OF SOUTH AMERICA. Succulent Plant Research 6: 133-244.
Comparison of pollen types.
fig. 1 Opuntia stricta - Pollen with reticulate exine (surface prominently reticulate)
fig. 2 Nopalea auberi - Pollen with almost smooth exine (surface not reticulate)