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 Subfamily in Cactaceae

Dictionary of botanic terminology - index of names

  Generally the Cactaceae  family is divided into three subfamilies (treated previously as tribes) : Pereskioideae, Opuntioideae, and Cactoideae. Recently a fourth group has been added, the subfamily, Maihuenioideae.  
Subfamily Pereskioideae (the leaf cactus)
With only about 20 species this subfamily is characterized by plant whit persistent broad, flat petiolate leaves and no glochids. Flowers are pedunculate, seeds large, shiny black, lacking arillus. Comprise only two genera Pereskia and Maihuenia (now moved in the subfamily Maihuenioideae) predominantly in South America. Habitshrub, tree, or in one species (P. aculeata) vines. They are likely a relictual group, possibly similar (but not identical) to the Cactaceae ancestor. As broad-leaved plants, their relationship to other cacti is not readily apparent, especially if flowers are absent. 
Subfamily  Opuntioideae
This subfamily is composed by about 300 species characterized by the presence of barbed hairs called glochids and by seeds having a stone-like aril (funicular envelope and accessory tissues) The succulents trees, shrubs, mat-forming subshrubs, and few geophytes of subfamily. Opuntioideae have mostly very short-lived, terete, cylindric, or conic leaves, usually present only on young growth and flowers.
"Splitters" will fragment the genus Opuntia into as many as 20 genera, while "lumpers" will take a broader concept of the genus and transfer the splitting to an infrageneric level. This subfamily has the most wide geographic range among major group of cacti, coast to coast (E-W) in both N. America and S. from central Canada to Patagonia, now successfully naturalized in southern Africa, Australia and in the Mediterranean.
Subfamily Cactoideae
This subfamily with over 1,000 species, shows  extremes of morphology diversity ,  represent About 85% of the species diversity of the family. Probably 99% or more of the cactus cultivated in hobbyists collections are from this subfamily. Cactoideae are characterized by lacking of leaves (with a few exceptions, e.g., Corryocactus brevistylus) and extremely succulents, spheric, barrel-shaped to columnar or snakelike stems, seed with  hilum-micropylar region and by an intron loss in the chloroplast  gene rpoC1. This group shows many examples of parallel evolution within the cacti. for example, the morphological similarities of the north American "ball" cacti (Mammillaria, Coryphantha, etc. of  Tribe Cacteae) and the similarly structured members of the Notocacteae (Parodia, Notocactus s.str., Frailea). Today most cactologists recognize about eight to ten (presumably) evolutionarily independent lineages within this subfamily which are called TRIBES.  In North America: Tribes Cacteae [largest], Pachycereeae, Echinocereeae [incl. Leptocereeae], and Hylocereeae). in South America: Tribes Notocacteae, Trichocereeae, Browningieae, Cereeae, and Rhipsalideae.
Subfamily Maihuenioideae
Maihuenioideae is the smallest subfamily of Cactaceae family, comprises only two species of the genus Maihuenia found in relatively high elevation habitats of Andean Argentina and Chile; these are low growing mat or cushion-forming plants. With no glochids.







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