distinctiveness, whereas the variety rank is appropriate if the taxon is seen throughout the geographic range of the species.

Example

The pincushion cactus, Escobaria vivipara, 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

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