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  Tucson Cactus and Succulent Society

Monthly Meeting

  • July 11, 2024
  • 7:00 PM - 9:00 PM
  • Sky Islands Public High School

"Relationship amongst cactus subfamilies
Evidence from deciduous leaves on areoles

Presented by: Root Gorelick and Jackson Burkholder

For 30 years, biologists have used DNA to deduce evolutionary relationships amongst cacti. Consensus is that Pereskia and Leuenbergeria are the most basal (ancestral), while the highly succulent subfamily Cactoideae are the most highly derived. However, family trees based on DNA have been equivocal about relationships of the other two subfamilies, Opuntioideae (prickly pears, chollas) and Maihuenioideae (just two species of Maihuenia). By examining anatomy of areoles and leaves, we propose that Opuntioideae are the more closely related of those two subfamilies to Pereskia and Leuenbergeria. Opuntioideae glochids seem to be homologous to areolar leaves on Pereskia and Leuenbergeria. Those areolar leaves and glochids are deciduous and are both produced along the top edge of areoles.

Root Gorelick is a professor of biology at Carleton University in Ottawa, whose work revolves around cactus biology, evolution of sex in all organisms, and academic governance. Root loves botanizing in southern New Mexico and maintaining a cactus garden in Ontario that is snow-covered for over a third of each year.

Jackson Burkholder grew up attending Colorado Cactus and Succulent Society events and has been growing cacti and succulents for over twenty years. Jackson is currently the co-vice president of the Colorado Cactus and Succulent Society, and on the board of the Cactus and Succulent Society of America. He spends his time conducting plant anatomy research and taking care of his collection of primarily South American cacti.

We are always thinking of your safety and if you are not feeling well we ask that you join us on the internet Zoom presentation. If you're doing well and would like to attend, you are welcome to come and join us for this special in person presentation (masks will be encouraged but not required). This meeting will also be a Zoom program and will be an important educational and informational event you must see. Also, if using Zoom, be sure to log in to win a $25.00 gift certificate from TCSS or choose a copy of the new 3rd edition of the Field Guide to Cacti & Other Succulents of Arizona. Excellent plant give aways will take place at the in person meeting but that portion of the program, because of the recording, will not appear on Zoom. When leaving the live in person meeting, please enjoy great refreshments provided by our member volunteers and also, everyone can get a special free plant offered to you by the TCSS.


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Tucson Cactus and Succulent Society

PO Box 64759  -  Tucson, AZ 85728  -  Phone: (520) 256-2447  -   Email:

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