Regularity: Regularly occurring
Catalog Number: US 617434
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Verification Degree: Verified from the card file of type specimens
Preparation: Pressed specimen
Collector(s): B. Mackensen
Year Collected: 1909
Locality: Texas, United States, North America
- Holotype: Rose, J. N. 1911. Contr. U.S. Natl. Herb. 13: 310.
Life History and Behavior
National NatureServe Conservation Status
Rounded National Status Rank: NNR - Unranked
One favored hypothesis as to the origins is that the O. humifusa-O. macrorhiza-O. pottsii complex spread across the United States from the east coast to Arizona. Opuntia polyacantha originated in north-central Mexico and spread northward. Tetraploid O. macrorhiza came into contact with the east flank of O. polyacantha and hybridized (probably repeatedly, even at present), producing the highly variable taxon referred to here as O. tortispina, which then spread eastward onto the plains. Opuntia tortispina has hexaploid members, presumably from unions of reduced and unreduced gametes. Those hexaploids apparently hybridize with hexaploid O. phaeacantha and add further to variation of O. tortispina. Many of these variations have been formally named or since treated as synonyms of O. macrorhiza.
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