"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.
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