A Neotropical Savanna

A couple of years ago someone in a comment to my post on cecropias asked whether cecropia trees were deciduous or evergreen. I had mentioned that the leaves, being big, could become unsightly when many of them dropped from the tree. The image to the left. is of one such leaf. My response was based on my own temperate-climate viewpoint, supported by some Cecropia references and an entry in wikipedia which states that (in botany and horticulture) deciduous plants “…are those that lose all their leaves for part of the year.” I said that “my” cecropia was an evergreen tree because it never lost all its leaves.

The answer did not satisfy me, though, and the question has been nagging at the back of my brain ever since. What is going on with deciduous trees in the tropics? At first I thought that maybe deciduous trees here lost their leaves in the dry season, which would make sense for water conservation. And indeed I did see some trees without leaves at that time. But other trees would lose their leaves at other times of the year, and some trees would lose some of their leaves, but not all of them, seemingly throughout the year.

Finally, I’ve located a paper that is readable, a classic in tropical biology, and that explains what’s going on with deciduous leaves in the tropics. I’ll be quoting and paraphrasing from it extensively throughout this post. The paper is by D.H. Janzen, written in 1975, and it’s called Ecology of Plants in the Tropics (Studies in Biology). To give you a sense both of his style and of the tropical environment, here’s a quote from the Introduction:

…in the same habitat there are tree species that are totally deciduous during a six-month dry season, species that are completely evergreen, and species that drop their leaves in the rainy season and bear them during the dry season.

In temperate climates, you’ll find a few conifers mixed in, say, an beech-maple forest, but you would consider such a forest deciduous because most of the trees there drop all their leaves every winter. None of the trees would lose all their leaves every summer.

Such information begs the question: why do trees drop their leaves? Read more »

Sometimes I think I should name this blog The Accidental Botanist. So many of my serious efforts at identification have ended up erroneous whereas I often stumble across an identification that just “clicks” with something I’ve seen recently. So it was with the nance macho, the common name in Spanish. [Nance is pronounced NAN'-say.]

I’ll get back to that name later, but one day I noticed a tree in bloom near the seasonal stream bed (dry now) that we cross whenever we leave our property. I took a few photos and thought that someday I’d sit down and try to figure out what it was.

Within a couple of days I was thumbing through Trees and Shrubs of Panama and saw a picture of a tree in bloom that almost exactly matched mine. (The tree below was one I spotted later on the road to Potrerillos, not the one by the stream bed. This image gives you a much better idea of the whole tree than did the stream bed photo.)

Since it seemed almost too good to be true that I would have my ID so quickly, I thought I’d better check the Trees, Shrubs, and Palms of Panama web site to see whether there might be other plants in the same genus or family that might cause me to confuse my plant with that in the book. Read more »

This vine belongs to the plant family Malpighiaceae, which is the family of the nance, a favorite fruit tree here in Panama. Because the family is represented only in the tropics and subtropics, I want to spend a little time comparing the parts of the nance plant with this vine, thereby looking closely at some of the family’s characteristics.

First, though, about that awkward family name – Malpighiaceae. I’ve heard botanists shorten it to something that sounds like “Malpiggy,” which I suppose is correct enough for pronunciation, but which sounds, in English, unjust to the Italian scientist for whom the family was named: Marcello Malpighi, a 17th century anatomist. We humans have a Malpighi skin layer, and we have Malpighian corpuscles in our kidneys and spleen. So why is a plant family named for him? Because he also looked at “plant anatomy” under the microscope and wrote a book about what he saw – the Anatomia Plantarum.

One plant feature he must have described in some detail are plant hairs that are attached to a plant by the middle of the hair, not at either end. There’s a sketch at Plant Families of the Dominican Republic, a site, by the way, that has an excellent description of the Malpighiaceae family.

The sketch shows the characteristic clawed petals of the flower on the left, the Malpighian Hairs at the top right, and the winged fruit, like the maple wing, at the lower right. It’s worth taking a closer look at the vine flower and the nance flower to see these details.

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The nance trees on our property have been in bloom for a couple of months, although they are just now really ablaze with color. All this time I’ve been trying to get a decent picture of an individual flower. This is not it – these are the flower clusters (inflorescences) on the tree.

The nance, Byrsonima crassifolia, is one of the three conspicuous trees in this savanna. It’s often a host for orchids,

and its fruit is used to make juice and to flavor ice cream. Different parts of the plant are used throughout the American tropics for medicinal purposes such as treating snake bites, diarrhea and dysentery, bad coughs, and reducing fever.

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