Dioon spinulosum

Thank you to Eric Hunt (Eric Hunt@Flickr) for today’s image of Dioon spinulosum taken at the Conservatory of Flowers in San Francisco. Dioon spinulosum is member of the Zamiaceae (one of the few families of cycads), commonly referred to as the sago-palms. This species is native to the Mexican states of Veracruz, Oaxaca, and Yucatan.

Like all cycads, Dioon spinulosum is a gymnosperm. Individuals of Dioon spinulosum have been estimated at ages of 500 to 1000 years old, and plants can reach heights of up to 16m (52 feet) tall, making it one of the tallest presently-living species of cycad! Dioon spinulosum is dioecious, producing one cone (either male or female) per plant about once every three years depending on environmental conditions. This particular species is said to produce one of the largest cones (if not the largest) of any gymnosperm. Female cones (like the one pictured above) can grow to over 80 x 30cm (≈32 x 11 in.) and can weigh up to 18 kg (≈40 lb). Male cones are slightly smaller, measuring around 55 x 10cm (≈21 x 4in.). Dioon spinulosum also forms coralloid roots, which play host to a number of symbiotic nitrogen-fixing species of cyanobacteria.

Cycads are often referred to as “living fossils” (a term coined by Charles Darwin), because their fossil records can be traced through to roughly 300 million years ago. It is thought that they once accounted for 20% of the terrestrial plant species during the Mesozoic/Jurassic eras, meaning they were likely forage for the largest herbivores to walk this planet, the dinosaurs!

However, recent research has discovered that the modern cycad species we are familiar with have appeared out of a “near synchronous rediversification globally around 12 million years ago”, which tragically contradicts a favourite theory of mine that dinosaurs were responsible for the present-day diversity in today’s cycads. See the paper by Nagalingum, N.S. et al. 2011. Recent Synchronous Radiation of a Living Fossil. Science. 334(6057):796-799. doi: 10.1126/science.1209926. (full PDF download). If you are interested in the ideas surrounding the coevolution between dinosaurs and cycads before the 2011 paper, see George Mustoe’s 2007 article in The Cycad Newsletter (Vol. 30(1):6-9): The Coevolution of Cycads and Dinosaurs. For some additional thoughts about the 2011 paper on the recent radiation of cycads and support for why the term “living fossil” may still be appropriate, see Jerry A. Coyne’s article: Paper on “living fossils” finds recent radiation, but misses the point. If all of that doesn’t get your blood moving, then I don’t know what will.

On a conservation note, this species is listed as endangered under the IUCN redlist. It is not alone amongst its cycad peers: approximately 65% of cycads are considered threatened or endangered. Unfortunately, their lengthy reproductive cycle and geographical isolation are not beneficial features when faced with climate change, habitat loss and overharvesting for sale as ornamentals. To learn more about all things cycad and to get involved with conservation efforts, visit the site of The Cycad Society or support the Fairchild Tropical Botanical Garden’s Cycad Conservation Initiative.

Dioon spinulosum

9 responses to “Dioon spinulosum”

  1. Daniel Mosquin

    Great entry, Bryant.

  2. Delia

    What an interesting plant! Thanks again for such an informative read.

  3. Michael Wall

    Fascinating. Great writeup on this interesting group of plants. This is such a fabulous website. Thank you also for noting the conservation issues.

  4. Michael F

    Worth noting from Nagalingum’s paper, that while the speciation within each genus is all fairly recent, the different genera are ancient, with Cycas splitting from the rest in the early Jurassic, and the other genera from the mid Cretaceous to the Eocene. So while dinosaurs may not have pressured evolution between species within a genus, they likely did do so for many of the genera. Since Mustoe’s paper deals with generic differences, his conclusions are not invalidated by Nagalingum’s paper.
    So: “which tragically contradicts a favourite theory of mine that dinosaurs were responsible for the present-day diversity in today’s cycads” – don’t worry, it’s still true!

  5. Eric Hunt

    Agreed – great writeup! Lots of good info.
    Of note – this is one of the oldest accessions at the Conservatory of Flowers. It first appeared on inventory lists in 1901.
    It has survived great challenges – windstorms and fires have damaged the structure during those 100 years, and it was grown off-site for a few years in the early 2000s while the Conservatory was essentially restored and rebuilt from the ground up.

  6. Adventure Nick

    What a fascinating plant – cycads are amazing & definitely prehistoric looking! Great shot of a very special plant

  7. kathryn corbett

    An interesting aspect of the cycads is the suspicion that ingesting the cones or inhaling the pollen of some species may cause a fatal neurodegenerative disease akin to ALS with dementia. Try Googling “The Cycad Pages”.
    Kathryn Corbett

  8. Bryant DeRoy

    I hear you Michael, all is not lost!
    Thank you Eric, for the details on the pictured individual, what a trooper it is!

  9. Trisha Mason

    I have sago palm growing in my front yard here on the Gulf Coast of Texas. It is a commonly used ornamental for landscaping here and tends to make itself at home quite easily. I’ve lived with this palm for 20 yrs now and seen it propagate (there are now four or five other trunks surrounding the original plant) and put out some eye popping cones. Devastating heat, humidity, drought, hurricanes, freezing cold, raccoons, armadillos, you name it, nothing has bothered this plant. It just keeps on truckin’.

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