A variety is a recognised division of a species in botany, next below the rank of subspecies; in zoology, species are only divided into subspecies and never into varieties.[1]
The pincushion cactus, Escobaria vivipara (Nutt.) Buxb., is a wide-ranging variable species occurring from Canada to Mexico, and found throughout New Mexico below about 2600 m. Nine varieties have been described. Where the varieties of the pincushion cactus meet, they intergrade. The variety Escobaria vivipara var. arizonica is from Arizona, while Escobaria vivipara var. neo-mexicana is from New Mexico.
A domesticated variety of a plant is called a cultivar, while a domesticated variety of an animal is called a breed.
A cultivar is indicated with a cv. and by putting the name between single quotes, not in italics, and capitalised, e.g. Aeonium arboreum cv. 'Atropurpureum'.
A strain, especially in bacteriology, is a collection of descendants of a single significant ancestor, and is sometimes used interchangeably with 'variety' but this is not strictly correct. A strain of animals is usually called a bloodline.
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