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Plant Atlas
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What has happened to Opuntia?
By Jon P. Rebman, Ph.D. The cactus family (Cactaceae) is divided into three subfamilies: the phylogenetically basal Pereskioideae, the Opuntioideae (the subfamily we are focusing on for this article), and the most derived and speciose Cactoideae, comprising some 80% of all cacti. The Opuntioideae (frequently referred to as opuntias or opuntioids) differ from all other cacti in having glochids (small, barbed, and deciduous spines) and seeds that are completely enwrapped by a funicular stalk, which becomes hard and bony. The largest genus in this subfamily is Opuntia, and in its very broad sense numbers perhaps 200 species. In our region of Southern California, the opuntias are our most diverse cactus group. For example, the flora of San Diego County includes 8 cactus species (barrels, pincushions, hedgehogs, etc.) in the Cactoideae and 18 species of opuntioids. These include all of the cacti that we commonly call prickly-pears (or nopals and sometimes tunas referring to the nopal fruits), chollas (or jumping cacti), and club-chollas (or horse-cripplers).
The large genus Opuntia (Cactaceae), which until recently included all of the prickly-pears, chollas, and club-chollas, is being taxonomically split up. For many years all of these different opuntioid cacti have been classified as one large genus with varying numbers of subgenera recognized within it. However, due to a new consensus among modern cactus taxonomists, especially with the aid of molecular studies, the genus will be divided and many of the subgenera will be lifted to the generic level. In respect to these nomenclature changes, the opuntias of the United States now total 5 genera, 61 species, 18-20 additional varieties and many interspecific hybrids. The new taxonomy of opuntias
The current classification of opuntioid species for the United States recognizes five genera (Consolea, Cylindropuntia, Grusonia, Nopalea, and Opuntia) that were previously part of the broadly interpreted genus Opuntia. The following accounts briefly describe each genus and its diversity in North America, north of Mexico. The true chollas (Cylindropuntia, fig. 1) have cylindric stem segments and completely deciduous spine sheaths. Cylindropuntia has 20 species, six additional varieties and at least nine named interspecific hybrids in the United States. The club-chollas (Grusonia, fig. 2) are low mat- or clump-formers with cylindric to spheric stem segments having spines with only the tips being sheathed. In the United States, there are eight species and one interspecific hybrid of club-chollas. The prickly-pears (Opuntia in the strict sense, fig. 3) have mostly flattened stem segments and are completely without spine sheaths. There are 31 species, 12-14 additional varieties and at least seven named interspecific hybrids in the United States alone. In the United States, two other genera of the Opuntioideae, Nopalea and Consolea, are found only in Florida. Nopalea has a flower modified for hummingbird pollination. The flower is somewhat tubular in shape with red to orange tepals that are almost completely closed, but with protruding stamens and stigmas. The Nopalea flower also has a nectar chamber covered by an extension of the style near its base. Just one species (N. cochinellifera) is found in the United States and has naturalized from cultivation in central Florida. The genus Consolea has short, orange to red, slightly bilaterally symmetric flowers, with wide-opening petals and a nectar chamber similar to that of Nopalea. There is one species in the United States, the nearly extinct native C. corallicola from the Florida Keys. It should be noted that at least one other opuntioid genus does occur naturally in the Museum's region of study, in the Cape Region of Baja California Sur. The genus Pereskiopsis has large leaves, spines, showy flowers, and stems that are not very succulent in appearance. Thus, many of the species look more like spiny shrubs or trees rather than the fat, succulent cacti that we are more familiar with. The species from the peninsula is called Rajamatraca (P. porteri), and it usually occurs in the Tropical Deciduous Forest (or Sinaloan Thornscrub) around the base of the Sierra de la Laguna. This cactus species is almost vine-like, and it clambers up the trees and into the canopy of the forests in this area. How does this affect us? This taxonomic change means that many of the species previously put into the genus Opuntia will now be recognized in other related genera. For example, the common Coast Cholla, which was previously recognized as Opuntia prolifera, will now be called Cylindropuntia prolifera. This same rule will apply to other regional chollas as well, such as Teddy-bear Cholla (Cylindropuntia bigelovii var. bigelovii), Wolf's Cholla (C. wolfii), etc. However, the scientific names for all of the prickly-pears will remain the same, i.e., Beavertail Prickly-pear (Opuntia basilaris var. basilaris) and Coast Prickly-pear (O. littoralis). Don't worry--if you don't like all of these taxonomic changes and new scientific names, please realize that our local opuntia cacti are still the same plants that we know and love. |
Fig. 1. Cylindropuntia bigelovii var. bigelovii (Teddy-bear Cholla), an example of the genus Cylindropuntia
Fig. 2. Grusonia invicta (a club cholla)
