By Robin Y. Rivet, for Let’s Talk Plants! December 2024.
Public domain: United States Botanical Garden. (Accessed 11/16/24) https://www.nsf.gov/news/news_images.jsp?cntn_id=124386&org=NSF
New Tree Taxes? Don’t Laugh.
Fasten your seat belts.
Although no one is going to “tax” your trees, tree “tax-onomists” are moving full-speed ahead using DNA analyses to update phylogenetic classifications. Unearthing species evolution is neither linear, nor tidy; and is seldom logical. What Linnaeus started as a universal binomial plant classification system (focusing on flower parts), has evolved into a staggering undertaking utilizing molecular biology.
Let’s take a drive.
In 1995, the genera Corymbia and Angophora were separated from Eucalyptus into three distinct morphologies. At that time, city planners reflexively avoided planting all “eucalyptus” locally; (often for uninformed reasons). However, the genus changes placed “provisional halos” on a few species like lemon, ghost and rose gums. Slam on the brakes now because the Eucalyptus genus has once again merged. Probably to stay this time. How many species are involved? Too many to cite here, but according to CalPoly SLO, there’s a lot of eucalypts that hold promise. And during the next 40-70 years Southern California will need “large climate-ready” and “small climate-ready” species. In fairness, tree characteristics have not changed, just how scientists categorize them.
Flowering Plant systematics - Angiosperm phylogeny poster, 2019Theodor C H Cole, Hartmut H Hilger, Peter Stevens, CC BY-SA 4.0 via Wikimedia Commons
Ironically, EUCLID cites this new research, but revising their massive identification database - remains an enormous task.
Trephina Gorge Ghost Gum is over 300 years old Tununda, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
A few eucalypt updates:
· Ghost gum: Corymbia papuana (species was in error) becomes Eucalyptus aparrerinja – climate ready
· Lemon-scented gum: Corymbia citriodora becomes Eucalyptus citriodora
· Red Flowering gum: Corymbia ficifolia becomes Eucalyptus ficifolia – climate ready
· Sidney Red gum (aka rose gum): Angophora costata becomes Eucalyptus apocynifolia – climate ready
· Spotted gum: Corymbia maculata becomes Eucalyptus maculata– climate ready
· Spider gum (aka bushy yate): Eucalyptus lehmannii becomes Eucalyptus conferruminata – climate ready
Now, loosen your seatbelt a little, as these changes may be familiar – but don’t get too comfortable.
· African sumac: Rhus lancea became Searsia lancea (formerly Toxicodendron lanceum) – also climate ready (it’s still in the Anacardiceae family - along with cashew, mango, and poison ivy) Yup, that toxic/allergenic genus.
· African Fern Pine: Podocarpus gracilior became Afrocarpus falcatus (although the similar yew pine and long-leaved yellowwood remain in the Podocarpus genus)
· Blue elderberry: Sambucus cerulea is now Sambucus mexicana (a native species)
· Brush cherry: Eugenia myrtifolia became Syzygium australe (this is truly a tree, not a bush)
· Floss silk tree: Chorisia speciosa became Ceiba speciosa (very beautiful) – also climate ready
· Jelly or pindo palm: Butia capitata –is now Butia odorata (capitata derives from cabbage, but odorata implies smells)
· Mandela plum aka kaffir plum: Harpephyllum caffrum became Harpephyllum afrum
We’re at the finish line, but there’s still a hairpin turn - or two...
The ubiquitous London plane tree that was widely planted as Platanus x acerifolia, is now called Platanus x hispanica. That “London” in its common name was always erroneous, as it was hybridized in Spain, not England. The new species name takes that to heart.
Conifers also changed, but gymnosperms follow separate lineage.
· Monterey cypress: Cupressus macrocarpa became Hesperocyparis macrocarpa
· Leyland cypress: Cupressocyparis × leylandii became × Hesperotropsis leylandii
“There’s no such thing as a tree (phylogenetically)” image used with permission ©Georgia Ray - https://eukaryotewritesblog.com/2021/05/02/theres-no-such-thing-as-a-tree/
Before you unbuckle that seat belt, consider the graphic and comments above:
Georgia Ray – is a trained microbiologist - and speculates in her Eukaryote BLOG that:
· “ ‘Trees’ are not a coherent phylogenetic category.”
· “Trees are regularly interspersed with things that are absolutely, 100% not trees.”
· “For instance: The common ancestor of a maple or a mulberry tree was not a tree.”
· “The common ancestor of a stinging nettle and a strawberry plant was a tree.”
You get what she is saying? Personally, I find her musings “riveting”.
Stop the car. Evolution isn’t over - it’s not done with us yet.
The quest to trace our human genealogy is similarly fraught with historic errors, misspellings and even intentional fabrications since family records can be as much wishful thinking - as fact. And Homo sapiens - as in “us”, don’t trace back that far; yet we manipulate the past with faulty assumptions. The fact is DNA testing doesn’t lie. Read more about taxonomy and its modern principles, as there’s a long road ahead.
Member Robin Rivet is an ISA Certified Arborist & UCCE Master Gardener – contact her: treetutor@gmail.com
Here’s one more list for the curious: Uncommon and misidentified tree species of San Diego.
Comments