Monday, May 13, 2013

The last of the palms: Otto von Bismarck's tree

Species name: Bismarckia nobilis

Common name: Bismarck palm

Location: Dominican Republic

Well, we have finally come to the end of my images from Dominican Republic, and this is my last plant species to profile from my lovely vacation in February (I can't believe these pictures have lasted me until May! I need to go on vacation more often...). I figured since it's the last one, I should probably go out with a bang...

The Bismarck palm is native to, like almost all palm species, Madagascar and is declining in numbers there (like many, if not most, of their endemic plant species). The fertile land is being cleared and converted to agriculture, with a few select trees being saved to represent landmark "specimen trees" throughout the landscape. Bismarck palms can be incredibly long-lived, have enormous canopies if given enough space, and provide great shade and habitat for other species. By leaving even just a few Bismarck palms, Madagascar is potentially saving tens of species who use these trees as refuge. Unfortunately, agricultural crops are worth far more money to the economy of Madagascar, and these trees likely don't stand a chance of sticking around for long. It's a shame; a country that was once one of the most biodiverse locations in the world is now becoming a barren agricultural landscape. I know I've poo-poo'd on Madagascar in a few blog posts, but the more people know about their biodiversity crisis the more that can be done about it. World economies really need to start putting pressure on countries that house the most diversity to stop cutting down forests because the species themselves have some sort of economic value. It's a slippery slope once you put a price on diversity, but it's true what they say in the business and commerce world: Money talks. Fortunately for the worldwide population of Bismarck palms, they are planted in huge numbers around the world as ornamental species (in the tropics and sub-tropics; they can actually survive temperatures as low as -6 degrees Celsius for short amounts of time). There are two main varieties of this tree: the green kind that's pictured above, and a variety that is almost blue because of a very thick layer of wax that is deposited on the outside of all of the leaves (which you might guess would be much more tolerant of drought and cold snaps; you would be correct with that assumption).

Bismarck palms are some of the most easily recognizable palm trees in the entire world...once you know what you're looking for. They have characteristic fan-shaped fronds with a very thick petiole connecting the leaves to the trunk of the tree. These petioles, as you can see from the image with the pink arrow, are curved presumably to allow the fronds to sway from side to side but prevent the snapping of the fronds if shaken up and down (since we all remember from elementary school that an arch is much stronger than a straight line...right?). This also provides a really unique habitat for animals, other plant species, fungi, and even bacteria since all of the rain that the fronds catch is funnelled down the petiole towards the trunk of the tree. Because the bases of these petioles are so warm and moist, they usually rot right off the tree before the leaf has a chance of dying, especially in very warm, wet areas. The inflorescences produced are also quite characteristic, and look a bit like marine ropes emerging from the base of a leaf. These mature into flowers (some male flowers are pictured in the 8th image; you can tell because they are full of stamens and very little of anything else), which either produce pollen or ovules. These trees, like the pacaya palm (which you can read all about HERE), are dioecious meaning one plant either produces male or female flowers but never both. The trees with the female flowers end up producing the fruit, which starts off green when immature and ripens to be yellow or brown (you can see the green fruit in the bottom image). The fruit are not reported to be edible by humans, although I'm sure someone somewhere has tried them. These are the preferred fruit of some birds and other animal species, so these trees do play an integral role in the food webs of the ecosystems they're living in.

I keep mentioning that these trees are integral parts of their ecosystems, so I think it's about time to show you what I mean. In the two pictures below (the same image, the first one is unaltered and the second one has a bunch of boxes around interesting features) you can see symbiotic plants and animals all living in the same tree:

The green and yellow boxes show the fruit of the Bismarck tree: the green box shows the immature green fruit and the yellow box shows the more mature yellow and brown fruit. Inside the pink box are three different species of plants, the heart-shaped leaf vine, the oval-shaped weedy plant, and the roundish-shaped weedy plant. What these species of plants are I have no idea; they were about 15 meters in the air and I wasn't about to climb the tree to find out! There are also a whole lot of sticks at the top of the tree, which is weird (in the purple box). In fact, I'm guessing that's the way those three plant species managed to make it up into the top of that lone tree; there are no trailing stems or roots to suggest that they "climbed" up there. In the orange box we have a lone bird, who seems to just be hanging out on an old petiole of a leaf. But is he really?

Well, Mr. Bird there isn't actually just hanging out on a petiole by chance; he's protecting his nest. Yes, that massive thicket of twigs was more than likely made by that ridiculously tiny bird (you probably are aware of the species; we call them "that brown bird that makes all the noise at 5 am during the spring" and this common name probably reflects about 500 species of bird). In fact, we stood under the tree for a while and watched more than one of these little brown birds fly to and from the nest; there's likely a whole family of them living up there. In hindsight, it was probably pretty stupid standing under the tree staring up at them (not that I'm afraid of a tiny brown bird or anything): if you're really observant you'll see white patches all over the underside of the palm fronds. Those aren't patches of fungi. Those are patches of "bird paint."

Here's another example of plant species that exploit this tree. Again, I have no idea what species this is since they're just tiny seedlings, but these are growing from seeds that would have been blown down those arc-shaped petioles and landed at the base of the leaf where there is likely an accumulation of organic material that is damp and warm: perfect conditions for plants (amongst other things) to germinate. These plants likely won't last long being squished into a petiole like that, but depending on what species they are they might be able to complete their entire life cycle without ever leaving the protection of their host plant. If those are species that are perennials or require much more space to grow, they'll likely die before producing anything substantial.

And, like I promised in my first blog post about pictures of plants I took while in the Dominican Republic, lizards also call this tree home. These pictures represent what is likely two different species of anole lizard (Anolis spp.) that are in all likelihood native to Dominican. If you think about it, these trees are absolutely perfect habitat for lizards to hide from predators in the petiole hollows, build nests at the bases of petioles, and jump from leaf to leaf to catch bugs to eat. They were pretty curious as to what I was doing holding a camera so close to their home; I guess I did neglect to ask them permission to photograph their treehouse. Next time I'll make sure to bring "lizard waivers" with me!

I hope you've enjoyed the rather long series about "Plants in the Dominican Republic" over the last few months!