Saturday, December 13, 2014

From Aloe to Aloiampelos, Aloidendron, Aristaloe, Gonialoe, Kumara

Taxonomists—scientists describing, naming and classifying organisms—love change. They are constantly assigning and reassigning plants (and animals) based on the latest research findings. The decisions they make often annoy gardeners: After all, why is it necessary to move a plant that has always been one thing into another bucket, causing its botanical name to change? Sometimes these things seem haphazard, but I’m sure they’re always scientifically motivated. Or at least I hope so.

Most of the time the work taxonomists do attracts little attention among the gardening crowd, myself included. However, when an entire group of plants I’m fond of is affected, my ears do perk up.

Case in point: the recent reclassification of the genus Aloe. Molecular studies suggest that not all aloe species have the same evolutionary origin and hence are less closely related than previously thought. Based on those findings, some species have been separated from the genus Aloe and moved into their genus. While only a relatively small number of species is affected, they do include some very popular garden plants, as you will see below.

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Aloe dichotoma, now Aloidendron dichotomum
(photographed at The Living Desert, Palm Desert, CA)

The first new genus is Aloiampelos. It consists of the rambling aloes, shrubby plants characterized by thin, slender stems that are often too weak to stand on their own and therefore require other plants for support. The most commonly grown rambling aloe are Aloe ciliaris (now Aloiampelos ciliaris) and Aloe striatula (now Aloiampelos striatula), the latter being one of the most cold-tolerant of all aloes (hardy to 15°F).

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Aloe striatula, now Aloiampelos striatula (photo Wikimedia Commons)

The second new genus is Aloidendron. It consists of the tree aloes: Aloidendron barberae, Aloidendron dichotomum, Aloidendron eminens, Aloidendron pillansii, Aloidendron ramosissimum and Aloidendron tongaense.

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Aloe ramosissima, now Aloidendron ramosissimus
(photographed at Poot’s Cactus Nursery, Ripon, CA)

I wonder how this change affects hybrids such as the ever popular Aloe ‘Hercules’. As a cross between Aloe barberae and Aloe dichotoma (now Aloidendron barberae and Aloidendron dichotomum), it presumably has new name now as well: Aloidendron ‘Hercules’.

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Is Aloe ‘Hercules’ now Aloidendron, too?
(photographed at the Ruth Bancroft Garden, Walnut Creek, CA)

The third new genus is Aristaloe. It’s monotypic, meaning it consists of only one species: Aristaloe aristata. I’ve always thought that this plant doesn’t really look like an aloe. It looks more like a large haworthia, and indeed parallel attempts have been made to move it, together with a few haworthia species, to yet another new genus, Tulista. Manning et al., however, propose the genus Aristaloe, and that’s what I’m going with for my purposes.

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Aloe aristata, now Aristaloe artistata
(photographed in my front yard, December 2014)

The fourth new genus is Gonialoe. It consists of three species, only one of which is common in horticulture: Gonialoe variegata, the partridge breast or tiger aloe. It’s a very popular plant in California, and easily found in nurseries, including big box stores.

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Aloe variegata, now Gonialoe variegata
(photographed in my front yard in 2011)

The fifth new genus is Kumara. This genus was first introduced in 1786, then abandoned, and now resurrected to include two very distinctive aloes: the fan aloe (Aloe plicatilis, now Kumara plicatilis), a very popular small tree aloe, and the rare and stunning Aloe haemanthifolia (now Kumara haemanthifolia), which I have only seen in photos.

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Aloe plicatilis, now Kumara plicatilis
(photographed at UC Botanical Garden, Berkeley, CA)

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Aloe plicatilis, now Kumara plicatilis
(photographed at UC Botanical Garden, Berkeley, CA)

Here is a summary of the changes described above:

OLD NAME NEW GENUS NEW NAME

Aloe ciliaris

Aloiampelos

Aloiampelos ciliaris

Aloe commixta

Aloiampelos

Aloiampelos commixta

Aloe gracilis

Aloiampelos

Aloiampelos gracilis

Aloe juddii

Aloiampelos

Aloiampelos juddii

Aloe striatula

Aloiampelos

Aloiampelos striatula

Aloe tenuior

Aloiampelos

Aloiampelos tenuior

Aloe barberae [Aloe bainesii]

Aloidendron

Aloidendron barberae

Aloe dichotoma

Aloidendron

Aloidendron dichotomum

Aloe eminens

Aloidendron

Aloidendron eminens

Aloe pillansii

Aloidendron

Aloidendron pillansii

Aloe ramosissima

Aloidendron

Aloidendron ramosissimum

Aloe tongaensis

Aloidendron

Aloidendron tongaensis

Aloe aristata

Aristaloe

Aristaloe aristata

Aloe dinteri

Gonialoe

Gonialoe dinteri

Aloe sladeniana

Gonialoe

Gonialoe sladeniana

Aloe variegata

Gonialoe

Gonialoe variegata

Aloe plicatilis

Kumara

Kumara plicatilis

Aloe haemanthifolia

Kumara

Kumara haemanthifolia

Note that the vast majority of aloe species are unaffected by these developments. They remain in the genus Aloe.

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You might ask yourself what all this mean for you, as a gardener or plant collector. In the short term, probably very little. Nurseries will continue to use the old names for years to come. I don’t know what effect this has on succulent clubs that organize shows and competitions. How does the Cactus and Succulent Society of America deal with sweeping changes like these? Will they switch to the new names right away or will they cling to the old names? I don’t really know the answer.

As for myself, since I’m aware of these taxonomical changes, I will begin to use the new names immediately. So don’t be surprised when you see a photo of my Aloidendron ‘Hercules’. It’s the same Aloe ‘Hercules’ as before, just with a slightly more challenging name.

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REFERENCES:

Hodgkiss, R. J. (2014). The Aloe Page. Retrieved from http://succulent-plant.com/families/aloaceae.html

Manning, J., Boatwright, J. S., Daru, B. H., Maurin, O., & van der Bank, M. (n.d.). A Molecular Phylogeny and Generic Classification of Asphodelaceae subfamily Alooideae: A Final Resolution of the Prickly Issue of Polyphyly in the Alooids? Retrieved from http://goo.gl/2uvvNp

Manning, J., Boatwright, J. S., & Daru, B. H. (n.d.). Aloe and Goodbye: A New Evolutionary Classification of the Alooids. Retrieved from https://barnabasdaru.files.wordpress.com/2011/12/alsterworthia.pdf

Walker, C. C. (n.d.). All change in Aloe and Haworthia. Retrieved from http://goo.gl/G2xg4W

25 comments:

  1. Cool writeup, thanks for sharing the info. It's going to be hard to remember that Aloe plicatilis is Kumara plicatilis, but I guess we'll manage somehow. Fantastic pictures in this post as well.

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    1. I think I'll be able to remember Kumara and Aloidendron eventually, but Gonialoe? It sounds vaguely obscene to me, LOL.

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  2. My brain hurts. You're so good with all this I have a hard time, thanks for summing it all up though, and that nice chart.

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    1. I must admit that taxonomy appeals to half of my brain because it's so precise and orderly, but the other half--the chaotic part--wants to scream. Although I look forward to walking into a nursery and asking them if they carry any Aloiampelos.

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  3. Oh my, looks like taxonomists have been at it again just to confuse us all eh? Will try my best assimilate them all, let alone remember...

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    1. There was some shuffling of other alooids (aloe-like plants) that I decided to ignore in my post because it affects species uncommon in cultivation. I did enjoy trying to decipher the very dense lingo in these research reports. Keeps my brain young.

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  4. So what's Aloe polyphylla then? It seems there are still lots of missing gaps...

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    1. Aloe polyphylla, like the vast majority of aloes, remains in the genus Aloe. I can see how the blog title I chose might lead people to think that the genus Aloe is no more. That's not the case.

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  5. Retraining this old brain will take some time. Thanks for the new list to remember Gerhard.

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    1. I wonder what's next! Might the genus Agave be ripe for some reclassification?

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  6. I can see why they did what they did, especially plicatilis and aristata that seem quite distinct from Aloe. Didn't know about the variegata.

    Though probably in a decade or two, the taxon people will put them all back into the same genus again. I think that is how it works. The old botanists who have seen this stuff say this is what happens: argue, combine genus, argue, split genus, argue, recombine...

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    1. I agree completely re: plicatilis, aristata and variegata. These have always looked like outliers to me.

      I wonder how much arguing was (or is still) going on behind the scenes and how many other taxonomists don't agree with these changes? All of this happened very recently.

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  7. Either this was just announced very recently or you only found out about it -- you were telling me about "Aloe ramosissimum" just a few days ago... :)

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    1. Alan, I just found out about this. The definitive article on this issue was published earlier in the year in the journal Systematic Botany.

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  8. Until it sinks in, feel free to correct my posts!

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    1. Don't count on me to remember. I thought I would but just this afternoon I decided to finally plant my Aloe plicatilis in the ground and not for a second did my brain tell me that it's Kumara plicatilis now. So definitely incomplete recall on my part.

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    2. And San Marcos Growers claims Aloe plicatilis has now become Kumara disticha, included in their entry on 'Hercules': http://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=3330

      Oy!

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    3. Kumara disticha was the name originally suggested in 2013, but that has been superseded by Kumara plicatilis, i.e. just the genus is different, the species remains the same.

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  9. Wow! I saw Denise's post and checked Google for more information. Your article was the clearest one I found on the changes and I'm pinning it for future reference. Thanks!

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    1. Kris, thank you very much! I tried to describe the situation as clearly as I could. I left out much of the actual research that led to this reclassification because it was hardcore stuff!

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  10. Oh my, more fun name changes to learn. Thank you for the easy to use chart to which I'll be referring frequently as I have a couple of the renamed Aloes.

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    1. Until I've memorized the new names, I'll refer to these plants as SFKAAs (succulents formerly known as aloes).

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  11. Nice write-up. In the recent book "Tree Aloes of Africa - Van Jaarsveld & Judd" the new taxonomic classification and where it comes from, is explained. The book is available in the US from http://www.exoticplantbooks.com/detail/?product_id=1055

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  12. Gerhard,
    Back in the 90's, a researcher in South Africa, Alvaro Viljoen, was studying the leaf sap chemistry of aloes. He found that there were compounds present in Aloe aristata that also occurred in Haworthias, but not in other aloes. Naturally, this led to the suspicion that Aloe aristata arose as a natural hybrid between an Aloe and a Haworthia. When such a natural hybrid comes about, with each parent having a different pollinator, there is a risk that the resulting plant might not appeal sufficiently to either pollinator, and thus it could easily die out. But if it still gets pollinated by one or the other pollinator, it will rapidly evolve to conform to the preferences of that pollinator. If Aloe/Arisataloe aristata indeed descends from an Aloe-Haworthia cross, it was clearly the Aloe pollinator (sunbird) that continued to visit it, since its flower has very much converged toward an Aloe flower. Now that independent new molecular evidence also supports separating A. aristata from other aloes, I think that this scenario is exactly what happened.

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