Clusia the Autograph Tree
The leaves of the Clusia tree caught my eye the first time we walked around the abandoned pastureland that was to become our property. They are shiny, attractive, and succulent-like. Botanists say the leaves are “leathery” and I suppose it was that leather-like texture that caused someone to try scratching a word on the leaf. Not only is it possible to do that, but the word will remain as a scar on the leaf for the rest of the leaf’s life. For this reason, it is sometimes called the “autograph” tree. The local name for our common Clusia is copé, literally translated as “I won.” I wonder what is won under a Clusia tree.
Once you’ve lived among these trees, though, you’re able to see their beautiful flowers and exotic fruits. I began to want to know which species of Clusia we had. There are 300 species of Clusia in the new world tropica (Maas), but only five species listed in the Tree Atlas of Panama, which made me think I might be able to discover which species we had. However, despite the excellent illustrations in the Tree Atlas, I was not confident of any identification.
So I turned to Robin Foster of the Field Museum of Chicago, who in turn told me about Barry Hammel. Hammel, of the Missouri Botanical Garden, is in Costa Rica at this moment as I write and he is working on the Flora of Costa Rica Manual. He very promptly and kindly answered my email query and suggested that this Clusia might be C. pratensis, which is, he said, “…mostly known from the dry savannas of Panama.” He said that some of the characters that help one recognize this species are:
- the epidermis of the twigs peels off in fine strips
- the flowers do not produce stamens (male reproductive structures)
- it is mostly free-standing, as opposed to hemi-epiphytic (we’ll get into this shortly)
Let’s look at these features one at a time. When we do, I think we’ll see that Hammel is right.
The epidermis of the twigs peels off in fine strips
As soon as Hammel mentioned this characteristic, I went back outside and looked closely at a twig. Here it is. Notice the fine red wrinkly material on the surface of the twig.
When I rubbed my finger gently over the twig, the material came right off.
Check number 1 for C. pratensis.
Flowers do not produce stamens
To prove that the flowers of this tree do not produce stamens, I suppose I should have several dozens if not hundreds of photos of flowers without stamens. I don’t, but I can say that the flower in the next photo looks just like all the other flowers I’ve ever seen on this tree. In fact, one of the things that intrigued me early on about the flowers was the structure in the middle.
It turns out this central green mass is simply the female reproductive structure – the brownish (and very sticky!) ring is below the ovary and in some species this ring bears sacs containing pollen. There are, however, no pollen sacs or any other male reproductive structures in this species.
I had not known that a species could produce fruits without there ever being pollen involved. The term Hammel used was apomictic to describe the species – from apomixis, “[d]efined broadly as any form of asexual reproduction and narrowly, and more commonly, as seed production without fertilization.” [Harris] Wow.
So, check number 2 – this plant has no stamens – for C. pratensis.
Mostly free-standing
Clusia may be free-standing or they may be hemi-epiphytes. An epiphyte is a plant that “…grows upon another plant but does not draw food or water from it.” (Harris). Hemi- means “half,” so a hemi-epiphytic plant is “half-epiphyte.” Within the same species of Clusia there can be free-standing trees and trees that “half-grow” upon another. Clusia may not extract food nor water from the tree it half-grows upon, but it can certainly strangle such a tree, as I wrote about earlier.
It manages this hemi-epiphytic behavior by putting out “stilt roots” that, when they encounter another tree, begin to grow around it, until the trunk of the other tree is completely girdled. The red arrow points to the origin of this stilt root.
Most of the Clusia in our area, however, are free-standing, as is this young one.
So, check number 3, mostly free-standing, for Clusia pratensis.
So what does this word pratensis mean? According to Dave’s botanary it means “referring to a meadow.” Well, I guess meadows and savannas can be similar, so the name fits well enough.
This may not be the end of the Clusia story, though. Hammel mentioned in his email message that it is possible that two other species of Clusia may very well be present in our area, so now, Sherlock cap on head, it is time to go looking for more.
Thank you for spotlighting this fascinating tree and for your lovely photos. I suppose I shouldn’t be surprised that plants can reproduce asexually, since animals can do this, too, and as we know, plants are much stranger more interesting than animals!
However, it is curious that the plant retains a flower, since the whole point of the flower is to attract pollinators. Are those actually petals, or merely petal-like structures? Is the ovary right at the surface rather than located some distance below a stigmatic surface. IS there a stigmatic surface? And what purpose does the stickiness serve? As you can see, your post has got me wondering . . .
Finally, I love the name, autograph tree.
~Shelley
Hi Shelley,
Thank you so much for your thoughtful comment and questions. I myself am still so new at botany that I can’t answer all of them, but for what it’s worth, I’ll pass on a few things I’m learning as I’m going along.
A flower does more than attract pollinators, this much I know, because it is the female part of the flower that develops into the fruit. I’m learning to watch for this – how the style stays behind after the petals drop off. It then grows into, or more or less becomes, the fruit.
Yes, those are petals. If you turn the flower over, you can see the sepals underlying the petals, so the petals are what they appear to be.
You may very well understand as well or better than I about ovary position. Here’s what I know: it can be above or below the point of attachment of the petals. In this case it’s above. The stigma, however, does have to lead first to the pistil then to the ovary and I for one have not sorted out what’s going on with the green thing in the middle of this flower. Hammel said the ring was below the ovary, and so I just passed that information on.
Like, why is that ring sticky? Hammel did say that in some other species that ring contains anther sacs, so there may be some connection there, but I don’t know what it is.
So, I’m still wondering, too. Again, though, thanks.
I should have been more clear: the point of the showiness of flowers is to attract pollinators. If you compare angiosperms to gymnosperms, say, it’s easy to see that the former invests a great deal of energy on features to attract pollinators to the structure that contains the ovary. A pine tree, by contrast, produces a structure whose function is to simply capture wind-blown pollen. There is no effort to attract birds or insects because these don’t play a role in pollen transport. As a result, pine cones are rather ho-hum by comparison.
Nevertheless, it’s easy to see how a structure might have developed and then lost some its original function while retaining non-functioning features–in this case, the showy petals. Not infrequently, natural selection seems to produce Rube Goldberg contraptions, structures more complex than absolutely necessary. Or perhaps the petals do retain a function we don’t know about.
The mysteries of the plant world are a source of endless fascination, and I look forward to what else you and the neotropical savanna have in store!
~Shelley
Shelley,
Thanks for your great follow-up comment. I hope you continue to comment – and to open all our eyes to new ways of seeing these plants.
Mary
Great information Mary and comments from Shelley!
I was just on a hike in my neck of the woods of Panama last week and saw the open fruit with the red seeds (?), as shown in one of the pictures from your blog entry, and enjoyed the beauty and structure of them.
Thanks again for the good plant reporting.
Thanks for checking in, Michael,
Isn’t that fruit interesting? I need to take one apart next time I see one open. My memory may not serve me well, but I *think* that red part is just a covering for the seeds, kind of like a pod, and the seeds are a dark, but different, color.
I’ll comment back when I find out.
Beautiful pictures- and what a neat tree! It’s just amazing how much we don’t know about the world.
Beau,
You’re so right about how much we don’t know – and the tropics of course are so much richer than one could ever imagine from my little corner of Panama. Thanks for your comment.
Mary
Ooh neat! Thanks for teaching me about another great tree!
Thanks for checking in Vicky. It is a great tree, isn’t it? I really have been looking closely for those other species, now that I know about them, but I haven’t found one yet. Maybe I need to wander farther afield.
Mary
There is a horsechestnut tree in a courtyard in Amsterdam which Anne Frank used to look at (and wrote about) while she and her family were in hiding from the Nazis.
As a promotion, visitors to the Anne Frank House and the musuem’s website can sign up to add their name to a leaf on a virtual version of the tree (http://www.annefrank.org/content.asp?PID=785&LID=2).
It’s too bad Anne Frank’s tree is a horsechestnut. If it was a Clusia tree– visitors could put their names on real leaves!
I just went over to the site – thanks for the link. Very interesting.
Mary
DO THE ROOTS OF THE CLUSIA GROWS DOWN OR TO THE SIDE AND IF THEY CAN BREAK MY SEWER OR SIDEWALK, I DO NOT KNOW IF THEY THICK
THANKS PETER
Peter,
I don’t know whether the roots of a Clusia can break a sidewalk, but I would think it would take a large (and old) tree to do so. The stilt roots are above ground and are “looking” for other vertical surfaces to wrap around. They would ignore a sidewalk. In several areas where our Clusia trees are growing, there are no noticable bumps in the ground caused by underground roots.
Hope this helps.
Beautiful images of Clusia rosea, as well as nice blog.
If you like, pls check my post on the genus Clusia in Brazil, with photos of the beautiful Clusia lanceolata:
http://e-jardim.blogspot.com
Thank you, Marco,
Your photos are indeed beautiful – and it’s interesting to see a Clusia so very different from the one I’m used to.
For any English-speaking reader who wishes to go directly to the English translation of Marco’s post in Portuguese on the Clusia, you may go here:
http://tinyurl.com/blvcmr
Mary
[...] the surprise? Because we have many trees of the Clusia genus here, and their leaves are so smooth and leathery that I tended to generalize that feature [...]
Mary,
Your pictures of the Clusia are beautiful and your writing is wonderful.
Here in Florida we have the Clusia rosia which is very similiar to the species you are observing in Panama. It’s not widely used, and maybe that is not a bad thing. It is on Hawaii’s Most Invasive Horticultural Plant List maintained by their Dept of Land & Natural Resources. Certainly our climates differ but the C. rosia has some abilities that must be respected. As you mentioned they are apomictic and they also perform Crassulacean Acid Metabolism (CAM), a fascinating adaptation for dealing with water stress. Nature is amazing.
I was wondering if you or anyone else, has a picture of the male flower of the Clusia. Since it is not required for reproduction it seems to be anonymous.
bill
Hello Bill, and thank you very much for your kind words and also for your information about C. rosea being invasive in Hawaii. [Poor Hawaii - it's so vulnerable to invasive species! Some of my favorite plants here in Panama are invasive there.] Further, I had not known about CAM in Clusia. Thanks for that, too!
As far as male flowers, let me quote directly from Barry Hammel’s message:
The male flower may be anonymous because it doesn’t exist! I certainly have never seen any type of flower other than that shown in the post, and, believe me, I’ve been looking closely of late.
Mary,
Thanks for your reply. I emailed Dr Hammel too and he was kind enough to answer today. To paraphrase; he has not seen any staminate (male) flowers on Clusia rosea in herbarium specimens or in Costa Rica where he is currently. He does believe they exist, probably in South America, eastern Brazil.
Still it does seem like a “chicken or the egg” question. Did the apomictic abality of the female render the male flower unnecessary, or did the male disappear first and the female adjust to survive? Again, nature is amazing.
Great follow-up, Bill. I’ve been trying to educate myself about apomictic plants, and I found this entry at wikipedia, which you may find interesting.
http://en.wikipedia.org/wiki/Apomixis
It doesn’t exactly answer your (or my) questions, but it provides a good background, which, forgive me, you may already have.
Thanks for your interest. It’s so neat to hear from someone who has experience with Clusia and likes it so well.
Mary,
After a virtual trip around the tropics seeking information about the Clusia I’ve come back home, only to find one of the most distinguished experts of Clusia is here in my own back yard. Dr. John Pipoly works with the Broward County Cooperative Extension service in Ft. Lauderdale. I am a teacher for their tree trimming certification program and have met Dr. Pipoly on several occasions, but I was unaware of his Clusia expertise. If you would like to contact him his email address is jpipoly@broward.org, he is a wealth of knowledge.
Thanks for being the link that brought me the answers I needed.
Bill
Thank you, Bill. It’s wonderful to know who the experts are, and my experience has been that the experts are quite generous with their help.
Mary,
Have the Clusia’s produced seeds? Dr. Pipoli says that only one in fifty seeds actually germinate. Is that consistant with your observations? Are there specific animals, birds, insects that nest or feed in your trees? I would appreciate an update on your findings and experiences.
bill