A Neotropical Savanna

Last June, I saw a couple of galls on one of our very attractive trees, one in the myrtle family, called Myrcia splendens – the “splendid myrtle.” Galls, you may remember, are plant growths that have been stimulated by an insect. The growth serves as both home and food for the insect’s developing larvae.

After submitting an image of one of the galls to What’s that Bug? and learning that no one there knew what kind of gall it was (and they still don’t, as of today), I did a little searching on the internet and continued to come up fairly empty-handed. Last year’s galls were twig galls, or appeared to be so from the way they were attached to the tree.

Now there’s another type of gall on this tree – a leaf gall, which is a more common type of gall than a twig gall.

If you click on the image to enlarge it, you’ll see the leaf and how the growth appears to tuck into it. The leaf itself is producing this growth, of course, but it looks like the gall is just snuggling up to the leaf. You may be able to tell, also, that most of the leaves in this image are new – they’re a light green compared to the older leaves, which are dark green. Also, young flower buds can be seen here and there. This timing of the appearance of the galls brings home a statement from wikipedia on galls:

In order to form galls, the insects must seize the time when plant cell division occurs quickly: the growing season, usually spring in temperate climates, but which is extended in the tropics.

The insect naturally wants its home and food to grow rapidly, so here in Panama, anyway, this insect has chosen to settle on the splendid myrtle just as it’s putting out new leaves and flower buds.

Practically the only material I can find on galls and plants in the myrtle family is the observation that there are lots of them. In Australia, half the galls found have been on plants from the family Myrtaceae (Mo Bot Garden).

Worldwide, though, galls may be more likely to occur under certain ecological conditions than with specific plant associations. More species of galls are found in nutritionally poor habitats than in richer habitats. They are more likely to be found in association with woody plants that have leaves designed to conserve water than in association with plants without these characteristics (Fernandes et al., 2002). It happens that the splendid myrtle lives in nutrient poor abandoned pasturelands. It also happens that the shiny leaves of the splendid myrtle strike me – subjectively of course – as more likely to be water conservers than water wasters.

That’s about all I’ve been able to dig up. If anyone knows anything at all about galls here in Panama, or Central America, or the entire neotropics, please speak up.

Adjacent to the Davilla plant mentioned in the last post is a guava plant whose species I do not know. It’s in flower now, and I’ve been noticing that it produces a new flower every day, and overnight the petals wilt and the stamens (pollen-bearing male parts) begin to fall off.

Since my curiosity was peaked by the apparently rapid opening of the Davilla flower, I decided to watch the guava closely while waiting for a Davilla bud to decide to open.

Here’s what I saw this morning, between 6:54 AM and 8:05 AM. It took about an hour and a quarter for the flower to go from a bud to a fully open flower. (Click on any image to enlarge.)

And then, when I returned after 3 in the afternoon, here was the fully mature flower.

Now go back and look at all the images again, paying attention to the flower on the left of the blooming one. What happens to it is what is going to happen to today’s blooming flower tomorrow. First the petals wilt and the stamens begin falling away By mid-afternoon all the stamens are gone. Only the pistil (female part) remains and you can see the fruit beginning to develop beneath it.

Ain’t nature grand?

Technorati Tags: flowers, guava, petals, pistil, stamens

This is the story of two plants that belong to the guava genus. The guava is a tropical fruit native to Latin America. [Illustration from wikimedia commons]. As far as I can tell, the two plants belong to the same species, but they differ in a couple of ways that are puzzling to me.

The first plant grows in very poor soil – even poorer than the average on our abandoned-pastureland/depleted-soil property. We have a few areas that are so rocky and the soil so thin that the only way it can be maintained is by weed-eater. On this particular slope we have let some shrubs survive the weed-eater in the hope that some day the area will develop into a natural site for native trees and shrubs.

Looking from the top of the slope down toward the gully where rainy season rain drains into the quebrada (seasonal spring) we can see several shrubs. I’ve circled a shrub of interest, coming closer to it in the next photo.

This shrub is in fruit now and although I failed to get a photograph when it was in flower last February, I have reason to believe it is a guayaba de sabana (guava of the savanna), Psidium guineense, which is in the Myrtaceae family.

The second plant grows in a relatively richer area. I did manage to get a photograph of one of its flowers, and you can see the white petals and many stamens of a typical myrtle family flower. The area has fewer rocks than the slope and can be easily mowed. At various other places on the property, we have similar shrubs, and all of them seem identical to this second plant. The plant on the slope seems different from the rest in ways that you’ll soon see.

What makes me think it’s a guava?
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The more I learn about the Myrtle family of plants, the Myrtaceae, the more interesting it becomes to me. I already mentioned when writing about the Eugenia berries that members of the family include clove, guava, allspice, and eucalyptus. You can see from this list that the aromas can be quite spicy or strong. Now add to this list the aromatic wax bay berry and and the wax myrtle plant. These waxes are produced by plants in the genus Myrcia. The fruit surface of these plants is rich in palmitic acid – a fatty acid commonly found in animals and plants, according to wikipedia. The wax is removed in boiling water. Early settlers in the US made candles this way (Mabberley).

The unidentified tree in the gully, the one with the galls on it, belongs to this genus Myrcia. It was identified by a specialist in the Myrtaceae family at the Field Museum in Chicago, Lucia Kawasaki, and its full scientific name is Myrcia splendens. The potential waxy coat on the surface of this fruit is hinted at by its shine in the tree and perhaps even more so when seen close-up in a scan of fruits in various stages of ripeness:

However, Carrasquilla, the author of Trees and Shrubs of Panama, makes no mention of the use of the fruit for wax. He says the fruits are edible, sweet, and astringent. I think they’re sweet and spicy – maybe a little like allspice – but did not find them astringent. The bottom item in the scan, by the way, is the seed, not a small fruit. From that you can see that there’s not much pulp to the fruit. The seed is delicate and it’s easy to crunch right through it, thus destroying any pleasure from the sweetness of the fruit.

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