Sunrise (6:49 AM):

As the morning progressed and the flowers opened, it became clear there were two kinds of bees interested in this plant – a large one (circled), and a small bee. (or is it?), below. (The image below, as noted by a corresponden- with an Asian name I can’t translate – is a type of hover fly. I have some other images of the small bee, but they’re not clear enough to post.)

8:00 AM: At least a couple dozen bees were buzzing around. By 8:30 there may have been 50 or more. It was clear that the large bee, at least, was collecting pollen. My only image of this so far is fuzzy, but it’s not hard to see the orange pollen sacs.

8:30 AM: the first few weevils. The weevils are the entire reason I was sitting in the shade comfortably, with my coffee and notebook, watching this sandpaper plant put on its spectacular bloom. I had seen and photographed a weevil swarm last year, and Robin Foster of The Field Museum of Chicago suggested I look at the swarm more closely this year. I’m going to be tracking this plant throughout its blooming period to watch for these weevils.
That they are weevils has been verified by Dr. Henry Stockman who is this January at the Smithsonian Tropical Research Institute here in Panama and kindly looked at my images from last year. He suggested that it is possible that these weevils are eating the pollen – which is a rich protein source. As I watched, I could not see whether they were eating, but they certainly did not seem to be collecting it the way the bees were.
By the time the weevils arrived, some of the petals had already dropped from the flowers. The flowers had gone from opening bud at just before 7 AM to fully open flower, to the commencement of petal-dropping at 8:30 AM. One and a half hours. Astonishing!

9:30 AM: The number of bees was down and the number of weevils was up.

10:30 AM: The petals were seriously dropping off. I could hear the petals landing on the sandpaper-like leaves. They sounded like raindrops. There were even fewer bees, but the weevils were still there.

11:15 AM: Nearly all the petals were gone but several weevils stuck around. When the petals fall off, the cup-like green sepals, which underlie the petals, are left behind with the stamens. The weevils seem unperturbed by the absence of petals and simply crawl around the sepals looking for their pollen meal.

1:30 PM: The sepals were closing in on the stamens. A few weevils were still around, hoping to avoid getting trapped in the sepal jaws, I assume.

4:00 PM: The sepals are completely closed around the stamens. I saw one forlorn weevil crawling around on the sepal surfaces. Some sepals qwew separated enough to show yellow – they’re the ones that were bursting with petals to open the next day.

What a day for a plant! I’m sure Darwin would have loved the show. Remember his study of the “sleeping” leaves of the little machete plant, Erythrina? I wonder what he would have made of the opening and closing jaws of these sepals.

Several of the living fence post species are in bloom now. Living fence posts are fence posts that have sprouted after becoming a part of a fence. They can be obvious posts with a few sprouts coming out the top, or they can have grown into full size trees while still serving as fence posts.

The yellow-flowered macano was a living fence tree described last year, and the “little machete” or machetito that we’re looking at today and that is shown below is in the same family – the Fabaceae or bean family.

The Flowers
Surely you can tell from the flower where the common name came from – the red petal looks like the blade of a machete and the calyx (the cup of sepals at the base of the petals) looks like the machete handle.

While looking at the flower, we can ask ourselves to which of the three large groups within the immense Fabaceae family this plant belongs. You may recall that the three groups, or subfamilies, are based on flowers that look like 1) peas, 2) mimosa (flowers like soft spiny balls), or 3) Caesalpinia-like flowers, which are brightly colored and showy flowers such as found in Flamboyant trees.

So which is this? Since the flowers are definitely not soft spiny balls, we are left with peas and with the showy flowers of the Caesalpinioideae subfamily. If you go to Wayne’s World, you’ll find a discussion of this group of trees, which are called in English “coral trees.” He has dissected one of these flowers here to show how this machete blade is really part of a pea flower, with all the remaining parts being reduced.

Let’s defer further thoughts on the flower for now – we will shortly look at them more closely to see just why just the one part of the pea flower should be conspicuous.

The plant loses its leaves – is deciduous – in the dry season, so the flowers are easily seen on the bare branches in this photo on the left taken in January. Yet in July when the leaves are out you can, with a judicious zoom (right), also see the flowers. Clearly, flowers can be present in both the dry season and the rainy season, but during the dry season they seem to be fuller and more abundant.

The Leaves
The leaves are compound – 3 leaflets for every leaf stalk or petiole. They are arranged on the stem in an alternate fashion, although some of the petioles are so close together on the stem that it is hard to see whether they are opposite or alternate in arrangement. Both these characteristics – compound leaves and alternately arranged leaves – are typical of the Fabaceae family.

The Tree
The tree can reach 10 m or 32 ft in height, which I believe this old one may have done – if it hasn’t exceeded it.

Sometimes I have to pause – a tree like this in the bean family?

Well, yes, because of those alternate, compound leaves, and because the fruits are, after all, beans, as you can see in this image of all parts from the Tree Atlas of Panama.

I learned the scientific name of the machetito from Carrasquilla‘s book Trees and Shrubs of Panama – it is Erythrina rubrinervia. But how did botanists know to place it in the Erythrina genus?

First, we know now that the flower puts it in the pea subfamily of the bean family (the Papilionoideae subfamily of the Fabaceae family).

Next, we know that it has compound leaves with 3 leaflets per leaf stalk. This makes it a trifoliate leaf. Within the pea subfamily, the only tree genus with trifoliate leaves is Erythrina (Gentry). So, that was easy. Erythrina it is.

Erythrina – red colored
The genus name, Erythrina, means red-colored. There are about 112 species in the tropics worldwide, and about 36 in Mexico and Central America (Neill, Ann. Mo Bot Gardens). The species extends into South America, and some time ago it was taken to Hawaii and cultivated there.

rubrinervia – red veined
The species name also contains reference to the color red, but what veins are they talking about? The leaf veins don’t look red to me.

After studying all the images at the Tree Atlas of Panama site, I found this close-up of the leaf stalk (petiole) which shows glands at the base of each of the leaflets, but which also shows red streaks on the petiole. They aren’t true veins but they give that appearance.

So we have a red-colored flower with red streaks on the petioles, giving us Erythrina rubrinervia. It’s incidental that the beans are also red.

Darwin’s interest
Darwin studied Erythrina species of plants, among others, when he was investigating how plants move. He found that the leaves of Erythrina and other species “sleep” at night, by drooping toward the plant stem. During the day the leaves orient themselves to be perpendicular to the rays of the sun in early morning and late afternoon and “edge-on” to the rays of the sun at midday (Project Gutenberg EBook). There’s a great sketch of the process at the web site of faculty member Thomas Herbert at the University of Miami.

Now let’s get back to that machete-shaped flower.

Hummingbirds
Whenever you see a long, narrow flower, you may suspect that hummingbirds pollinate these flowers, and this is true for the Erythrina genus as a whole, whose flowers are particularly rich in nectar. In our area, the larger hummingbirds – the Swallow-tailed Hummingbird and the Black-throated and Green-breasted Mango visit Erythrina (wikipedia).

These are long-billed hummingbirds. But if you should see a short-billed hummingbird at an Erythrina rubrinervia, you may yell “Thief! Thief!” because it has been shown that while long-billed hummingbirds pollinate the flowers, short-billed ones steal the nectar (Cotton, in Biotropica)

The Little Machete
So the little machete tree is filled with wonders – its bean-ness, its red-ness, the way it moves, and its relationship with hummingbirds. Watch for it next time you pass a living fence.

You may have been able to answer immediately because you are very familiar with all three kinds of flowers, but what was it about this one that told you what it is? If you didn’t know what it was, don’t worry, the answer will be given later.

Orchids, lilies, and irises each belong to a different family: Orchidaceae (22,000 species), Liliaceae (1600 species), and Iridaceae (1500 species), respectively. Each family is widely distributed throughout the world. (Click on any image to enlarge.)

The flowers are so showy and beautiful that they’ve been thoroughly cultivated, and if you’re at all familiar with flowers, you can probably easily distinguish any of the three cultivated flowers. But what if you happen upon one in the wild?

It happened to our friend and naturalist, Michael. He sent around an image by email asking for guesses about a plant he found growing near his new home. He thought it might be an orchid but wasn’t sure. Our friend Carla responded with the tip that prompted this post (tip used by permission):

Peek straight into the center of the flower and look to see if it has long filament-like stamens holding pollen conspicuously on the tips. If yes, you might have a lily.

An orchid, however, would have a solid column holding two or more solid masses, called pollinia, which stick to pollinators, probably on the upper side of the throat.

What a simple and straightforward tip! So let’s look.

I couldn’t find a good image of a Tiger Lily (to keep the theme of the leopard-spot flower in the original image) that was not copyrighted, but here’s a lily that was blooming in our yard in early June this year. Click to enlarge or click on Hi-res for higher resolution options.

Hi-res

Nice long, filament-like stamens (male reproductive parts) holding pollen conspicuously on the tips (nothing more conspicuous than black pollen against a white petal!)

Now, let’s compare it with a much smaller orchid that bloomed in April of this year and that keeps the leopard-spot theme (no reason to do this, just fun). The image is a bit fuzzy – I can’t remember if the wind was blowing or whether I had a shaky hand that day – but you can tell that the interior of this flower does not resemble a lily in the least.

Hi-res

There’s the solid column holding two solid masses, the pollinia. As you might have guessed from Carla’s tip, the pollinia are carried away en masse from the flower. No dithering around with small pollen grains here.

Okay, so Carla’s tip had to do with orchids and lilies. Why did I bring in irises? Because when I went outside to start seeing for myself what Carla’s tip was all about, I saw the mystery flower at the beginning of the post. It’s an iris, and when I peek inside I see something a little bit in between the orchid and the lily.

Hi-res

The stamens are not long filaments with the pollen conspicuously at the ends. They are thick and the black pollen grains are on the side rather than the end. Notice that there are only 3 stamens, not the several we find in lilies. This is one of the distinguishing characteristics between lilies and irises. It may not be so easy to tell that these pollen grains are not glued together into pollinia, but if you were to take this flower apart, you’d see that there are 3 distinct stamens, not the one column that you see in orchids, and you’d see the individual pollen grains crumble off.

So there you have it. A simple way to tell lilies from orchids and even from irises. In short:

• Lilies have long stamens with conspicuous pollen at the ends.
• Irises have only 3 stamens.
• Orchids have one column supporting two or more packages of pollen called pollinia.

The answer, then, to the question at the beginning of the post is: you can tell that this flower is an iris because it has 3 stamens and no pollinia. And, by the way, Michael’s flower was an orchid.

Other differences, of course, can be found among these three families, but these differences are fun and useful, in my mind.

Update: The iris has a scientific name! It was recognized as Neomarica longifolia by user tem0dium on Flickr. With that head start, you can expect a closer look at it sometime in the future.

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.

Malpighi flowers have claws

Here’s a closer look at the vine flower,

compared with nance flower.

Look at the bumps between the claws of the petals – they’re green in the vine flower and yellow in the nance flower. These are oil glands. Many flowers in the Malpighiaceae family are pollinated by bees that collect oil from the flower while pollinating it.

The flowers occur in clusters, although the clusters differ between the vine (at the left, below) and the nance tree (right, below).

Malpighi fruits are variable

We could not use the fruits of these plants to place them in any particular family. The fruit of the vine is a winged “samara,” which is the fruit of elms and maples (the vine samara, which occurs in 3s, is shown in the two images on the left, below). The nance fruit is a fleshy fruit formed from a single flower, a drupe, with one seed inside (the image on the right – the nance fruits are the ones in the bottle).

Malpighi leaves are simple and opposite.

Leaves may be simple or compound. Malpighi leaves are simple, consisting of one blade; each leaf bud produces only one blade.

Leaves also may be opposite, alternate, whorled, or spiral. If opposite, the blades are exactly opposite each other on the stem. Malpighi leaves are opposite, as you can see here. The vine leaves are on the left, the nance leaves on the right.

Malpighi plants may be lianas or trees

Lianas are woody vines that start at ground level and climb trees to reach as much light as possible. They are common in rainforests, but also are found in temperate zones. Clematis, for example, is a liana (wikipedia). Today’s plant is growing on the ground in a disturbed area and has started climbing nearby shrubs. Nance is a tree. The vine, or liana, is on the left, the nance tree on the right.

Malpighi plants may have stipules

Linneaus himself, “Father of Taxonomy,” came up with the term stipule. A stipule is an outgrowth on either side of the base of the leaf stalk. In today’s plant, the stipules are small, scale-like, and triangular. You’ll need to click on the image at the left to enlarge it enough to see the stipules. Zero in at the point where the leaf stalks meet the stem. The nance stipules, by contrast, are relatively easy to see although you’ll probably want to enlarge the image on the right to see them better.

Finally, Malpighi plants have Malpighian hairs

You may have noticed the reddish hairs on the nance stem and leaf stalk in the image above, but it may not have been easy to see the hairs on the vine plant. Here’s a larger version of the underside of the leaf, but even so you may want to enlarge it to see the hairs well. While you’re looking, you may notice the swelling of the leaf stalk just at the base of the leaf blade. Those are leaf glands, and are common in the Malpighiaceae family.

To summarize the Malpighiaceae family characteristics that this vine and the nance share, then are:

• Flowers with clawed petals
• Simple, opposite leaves
• Stipules
• Malpighian hairs

We also looked at their fruits, which are not a family characteristic, and we saw that one is a vine, the other a tree.

Now to classify, as far as possible, the vine itself.

I used Gentry‘s field guide/key to the woody plants of Northwest South America to get a handle on the species. Gentry divides the Malpighiaceae family (about 60 genera) into two large groups:

1. Trees and shrubs with unwinged fruits [the nance tree (genus Byrsonima) goes here]
2. Lianas with wind or water-dispersed fruits [today's vine plant goes here]

He then breaks down each group into smaller groups. The small group into which this vine falls is the group with maple-like wings. He puts four common genera into this group. I’ll only discuss the one that seem most feasible to me: Stigmaphyllon.

Genus name

It’s because of Stigmaphyllon that this post has the title it does. The name Stigmaphyllon comes from “stigma,” which is the part of the female structure that receives pollen during pollination, and “-phyllon” which means “leaf.” According to Arthur Gibson, Garden Director for the UCLA Botanical Garden, … each stigma bears a very conspicuous leafy portion next to the sticky stigmatic tip. Once I started looking for the three leaves, I found them. Here’s a close-up of the center portion of the flower:

You can easily see those leafy structures at the right. On the left you see the green oil glands of the sepals.

Gentry states that the leaves of Stigmaphyllon usually have a heart-shaped base and those that don’t have such leaves do have unusually large glands on the leaf stem. These descriptions make me a little uneasy, because the leaves on this vine are elliptical, without a heart-shaped base. Further, I don’t have enough experience to know whether the glands on the leaf stem are unusually large. Nevertheless, Stigmaphyllon is the best fit I have for a genus.

Species name

As far as species… Discover Life lists 18 species in the genus Stigmaphyllon (do a search for Stigmaphyllon to see the list). Only 4 species have illustrations, but one of them is S. ellipticum, which seems awfully similar to this plant, and nearly satisfies my concern about leaf shape. Certainly the species name is encouraging!

Having been stung on species identification before, however, I’m assigning this plant an extremely tenuous identification: Stigmaphyllon (probable genus) ellipticum (possible species). The proper botanical name would be Stigmaphyllon ellipticum (Humb., Bonpl. & Kunth) A. Juss. In the meantime, I’ve saved a sample in my plant press and hope to get a real identification one of these days.

It was identified as a Costus species by a couple of good folks at Flickr. Being nutty about words, I started by tracking down the word Costus and found, in Dave’s Botanary, that is derived from the Sanskrit name Kushtha. Okay, so then I had to find out what Kushtha was. Turns out it’s a medicinal plant in a group of plants completely unrelated to the Costus group of plants. So, that’s peculiar and of no real help to me. Someday maybe I’ll find out why these flowers were named after other, unrelated plants.

I was, though, able to find out more about the Costus group, and in so doing, ran across David Skinner’s site, GingersRus. It turns out that Costus are closely related to gingers, sometimes being grouped in the same family with them. The Costus group are often called spiral gingers because their leaves spiral up the stem. The spiral is not terribly obvious in the image below, but it’s there, and accounts for asymmetric look of the leaves along the stem.

Back in 1922, when W. W. Rowlee described Costus in Central America (Bulletin of the Torrey Botanical Club) he said, “In any given locality the species do not usually appear abundant, but are scattered about in deep woodlands and undisturbed jungle.” Here’s this plant, in this woodland (although not deep within it), and it’s the only one I’ve seen along my walk, which is about a kilometer long.

Notice the long, thick stems. These are true stems, not the pseudostems (a pseudostem is formed from sheaths at the bases of the stems, like grass) that members of the ginger family, Zingiberaceae, have. The true stems of Costus are substantial enough to look like sugar cane. When I showed a picture of this plant to a Panamanian friend, he immediately said, “Caña agria.” “Caña agria means “bitter cane” and Rowlee reported that Costus were called bitter cane at that time, in 1922.

Costus are Monocots

Flowering plants are divided into two great groups traditionally called monocots and dicots. Wikipedia has such a great description of the value of monocots that I can’t resist quoting extensively:

Monocots comprise the majority of agricultural plants in terms of biomass produced. There are between 50,000 and 60,000 species within this group…. The largest family in this group (and in the flowering plants as a whole) by number of species are the orchids (family Orchidaceae), with about twenty thousand species. The economically most important family in this group (and in the flowering plants) are the grasses, family Poaceae (Gramineae). These include all the true grains (rice, wheat, maize, etc.), the pasture grasses and the bamboos…. Other economically important monocot families are the palm family (Arecaceae), banana family (Musaceae), ginger family (Zingiberaceae) and the onion family Alliaceae, which includes such ubiquitously used vegetables as onions and garlic.

Many plants cultivated for their blooms are also from the monocot group, notably lilies, daffodils, irises, amaryllis, orchids, bluebells and tulips.

Costus are in the order Zingiberales

Current taxonomic systems usually place monocot plants in the class Liliopsida. Within that class is the order Zingiberales, which includes “… horticulturally and economically important plants such as the banana (Musaceae), bird-of-paradise (Strelitziaceae), and edible ginger (Zingiberaceae).” (Wikipedia)

Costus are in their own family, the Costaceae

Costaceae have fused infertile stamen, which form a large petalloid labellum – it looks like a tongue – that often functions to attract pollinators. In the image on the left, below, you can barely see the labellum in the center of the flower. In the image on the right, the plant is saying “Ah,” and you can see it a bit better.

The flowers in this family are generally solitary or aggregated in inflorescences. Here the inflorescence is at the head of the stem. It consists of bracts protecting the petals. Only one flower emerges at a time. You can see the small yellow buds of the next flowers.

This plant, the “porcupine costus” was identified for me by David Skinner at GingersRus. It’s full scientific name is Costus villosissimus Jacq. The stiff hairs on its stem, bracts, and other parts are described as “villose,” hence the name. The species is widespread from Nicaragua to parts of western South America, but is most common in Panama and parts of Costa Rica.

Costus villosissimus has bright yellow flowers. My camera is old enough that it can’t adjust very well to light conditions, and my Photoshop skills are nonexistent, so the above images don’t reveal the true color. I decided to bring a flower home with me and photograph it next to an Allamanda, which is a very common flowering trumpet vine in the area. Anyone who has seen an Allamanda will know instantly the color of the Costus villosissimus. It’s almost identical. Frustrating that the light conditions on our work bench are so much better for capturing true color than the conditions in the woods! (Costus villosissimus on the left below, Allamanda on the right).

Several species of Costus in the New World tropics are pollinated by hummingbirds or orchard bees (Kay, et al. American Journal of Botany). Nearly every morning I hear the buzz of a bee near this plant, but the one day I saw one (a big black fellow) I did not have my camera with me. However, at another time, I did get to watch this other creature for awhile. (You’ll have to click on the images to enlarge them.) He or she may have been looking for nectar outside the flower, among the bracts. But that’s a story for another day.

5 August 2007 Update: I’ve now seen another definite young Costus villosissimus plant along my walk – about 200 m from this one. Here it is:

Coincidentally, the view of this young plant makes it easier to see the spiral arrangement of the leaves along the stem. The portion within the rectangle in the image above is shown below, with the leaf stalks (petioles) highlighted in red. I think the spiral is pretty clear this way.

At any rate, there are also a couple more, smaller plants along the trail that might also be Costus. I’m keeping an eye on them.  It would certainly be nice to have that section of the trail ornamented with several  Porcupine Costus plants!

If you compare these plants in pairs, you’ll find other features besides color in common. The orchid and the milkweed package their pollen in little sacs called pollinia. The milkweed and the lantana produce nectar (the orchid does not), are not indigenous to Central America (the orchid is), and can be toxic to herbivores. All three are said to bloom year-round, but only the lantana does so in our backyard. All three are said to have the same pollinators, which brings us to the fame this group of plants has among some students and some botanists.

It has been suggested that they belong to a “floral mimicry complex.” But do they? And what is a floral mimicry complex, anyway?

First, the definitions. If you look up mimicry in wikipedia, you’ll find the definition and examples relate to animals. The idea is that a so-called non-harmful species, such as the Viceroy butterfly,

“mimics” -or looks like – a noxious species, such as the Monarch butterfly.

As a result, the Blue Jay, for instance, avoids eating the Viceroy as surely as it avoids eating the Monarch. The Viceroy gets “free” protection. It doesn’t have to take in a toxin from the milkweed, make it harmless to itself, but keep it harmful to its predator. A physiologically expensive proposition.

Seven types of mimicry has been described by zoologists. Two types – Batesian and Müllerian – are of interest here.

Batesian mimicry is named after Henry Walter Bates and is the type exemplified by the Viceroy and the Monarch. The mimic (Viceroy) looks like the model (Monarch) but does not share the trait (toxicity) that makes the model unappealing to the predator (Blue Jay).

Batesian mimicry could work another way – a mimic could imitate a model that provides benefit whereas the mimic does not offer that benefit. In this way we come to floral mimicry, the inverse of animal Batesian mimicry. Flowers, especially orchids, may mimic other flowers or even animals to fool pollinators. If we look at the three plants of interest today, we see that the orchid Epidendrum does not have nectar whereas the other two plants do have nectar. So one idea is that the pollinators of Asclepias and Lantana, having sampled their nectar, might also pollinate the orchid Epidendrum because it looks similar to the milkweed and the lantana.

In my opinion, this is a stretch, but we’ll come back to the idea later.

Müllerian mimicry. This type is named after Fritz Müller. According to wikipedia, “His great discovery was about the advantage one unpalatable species would gain from resembling another unpalatable species.” Thus, all bees and wasps that have alternating black and yellow stripes are instantly recognized as being dangerous and unpalatable.

For plants, Müllerian mimicry again would be the inverse of the zoological definition. If several plants that produced good nectar also looked alike, then pollinators, having learned about the one, would continue to sample the others, and all similar plants would then benefit by being pollinated. The mimics would be recognized as being good, rather than dangerous.

The appeal of the concept of mimicry in the three plants we’re looking at now is that both Batesian and Müllerian types of mimicry might possibly be demonstrated in them. The idea was proposed in 1966 for a course in tropical studies called The Biology of Epiphytes (Bierzychudek). It was hypothesized that the non-nectar-producing orchid mimics the milkweed and the lantana, thereby attracting pollinators to itself. An example of Batesian mimicry in plants.

By contrast, the lantana mimics the milkweed (or vice-versa) so that, by growing in similar areas, the pollinators will visit both plants. An example of Müllerian mimicry in plants.

At bare minimum, for the floral mimicry concept to apply to these three plants, they must have the same pollinators. Indeed, several kinds of nonstinging bees and several species of butterflies have been observed on all three plants. (Bierzychudek) The most common visitor to all three species seems to be the butterfly, Anartia fatima, of the family Nymphalidae. (Bierzychudek).

Anartia fatima images above from Green Hotels of Costa Rica (left) and Insectarium Virtual (right).

Fun
It’s time, then to summarize these concepts. “Asclepias and Lantana are presumed to be Müllerian mimics of each other while the nectarless Epidendrum is thought to be a Batesian mimic of the first two.” (Bierzychudek )

It’s fun to think about, isn’t it? These two types of mimics might be exemplified by three plants, each from a different family.

…if true
In 1981, Bierzychudek published a study that looked closely at the hypothesis. She predicted that more pollen should be removed from dense stands of the milkweed and lantana than from sparse stands. If Müllerian mimicry were a factor in attracting pollinators to the flowers, then this prediction should be true whether the stands were pure or mixed. She also predicted that the orchid should receive more visits when interspersed with the milkweed or with lantana than when growing alone.

She was able to test these predictions by observing the pollinator visits and also by counting the pollinia they collected. As mentioned, pollinia are sacs of pollen. You can find some excellent illustrations of flower anatomy and pollinia at this site, which includes the following helpful sketch from a milkweed (note that the word “pollinium” is singular for pollinia):

Her conclusion: “Although the three species have overlapping ranges and share pollinators, visitation frequencies in stands of different floral composition do not support this hypothesis. Flowers in high-density stands of the “Mullerian mimics” are not visited more often than flowers in low-density stands, so apparent increase in population density through mimicry does not appear to confer an advantage. The “Batesian mimic” is not visited more often when interspersed with the model than when alone.” (Bierzychudek)

So…probably NOT true.

Personally, as I mentioned earlier, I would be skeptical about including Epidendrum in the complex, anyway. Look at them again. The orchid, Epidendrum, is on the left.

True, the colors are similar, but if you scroll through Roxi Steele’s images from Costa Rica, you’ll see several other flowers with this orange/yellow color combination, most notably Psiguria bignoniacea, P. tabascensis, and Caesalpinia pulcherrima. It’s hard for me to believe that a butterfly, at its scale, would confuse an Epidendrum with either the milkweed, Asclepias, or with Lantana.

By contrast, to human eyes, the milkweed and the lantana look similar at first glance. In fact, when a visiting botanist first showed me the Asclepias in our back yard, I said, “Oh, that’s a lantana!” Then I looked again. Now I would never confuse them, but at first, my own mind imposed the known lantana pattern on the unknown new flower.

Still, though, I can’t imagine that a butterfly would confuse them! The flower is about the size of the butterfly itself. I’ve tried thinking about this on a human scale. I suppose a dining room table with a few plates of food on it would be relatively the same size to me as these flowers are to a butterfly. If I walked into a dining hall where food was on the tables, what would I be fooled by? From a distance, plastic food. That would be Batesian mimicry – plastic food offers me no reward. Hmm. Actually, it’s the tables that should mimic, or not, each other. Yellow tables mean appetizers; red tables, desserts. That would be Müllerian mimicry. Ugh. It’s getting hard to carry through on this analogy. Oh, well. You get the idea.

1981 to 2007

At any rate, what interests me is that 26 years after the publication of Bierzychudek‘s paper, some botanists still refer to the Epidendrum, Asclepias, Lantana floral mimicry complex. It was mentioned, with a caveat, in my deeply used book, A Guide to Tropical Plants of Costa Rica. It was mentioned by my visiting botanist friend. I’ve found it in a PowerPoint presentation that can be downloaded by students taking advanced botany at a prestigious university.

When I wrote to Paulette Bierzychudek about this conundrum, she modestly replied: “… it’s entirely possible that I’m wrong – that some other study has been or will someday be done that demonstrates that mimicry takes place. I don’t know of any. Still, myths die hard.”

A pretty good description of the situation was published in a paper entitled “Floral mimicry: a fascinating yet poorly understood phenomenon.” (Roy & Widmer) The first sentence of their abstract is: “Flowers of different species that resemble each other are not necessarily mimics.” How sensible!

Floral mimicry would be fun, in this case, if it were true.

Update 1: I’ve just learned that Bitty Roy (of Roy and Widmer, next-to-last paragraph) obtained her PhD under the direction of Paulette Bierzychudek. In the interest of full disclosure.

Update 2: In case I’ve given the misleading impression that all floral mimics resemble other plants that give benefit, it is at least possible that some floral mimics resemble other plants with undesirable traits. It has been observed, for instance, that both Asclepias and Lantana are unpalatable and toxic. Since they both occur in pastures, their resemblance may provide protection from grazing. (Bierzychudek). This possibility had not been tested as of 1981 and I do not know of it having been tested as of today.

When I get up close to it, I feel an odd deja vu. Only after identifying it, and finding its family and its elegant relative, did I come to understand why.

I figured this plant was not going to be all that easy for me to identify. It was and it wasn’t. I thought I had it figured out as Odontadenia macrantha, but luckily, Robin Foster of the Field Museum of Chicago caught my error. It turned out to be, probably, Mandevilla hirsuta. More on that in a bit.

Most of my books are devoted to trees and shrubs, not vines. The flower did remind me of periwinkles and the common (in Central America, anyway) allamanda or golden trumpet vine. Those flowers are in the Apocynaceae, or dogbane, family. However, my identification skills are still so naive that I thought it best not to assume the family name right away.

I turned to an online key, Discover Life Flora of the Neotropics which has a database of 8,246 kinds of plants. It’s designed for novices like me and takes one through a series of multiple-choice steps, which include region where the plant was found, altitude, habit (tree, shrub, vine, etc.), leaf arrangement, leaf shape, flower color, and a little more.

My leaves are simple, opposite, with smooth edges.

Also important, I thought, was the fact that when I pulled a leaf away from the vine, I saw a copious amount of milky sap, or latex.

So, with the characteristics I entered, I got 37 matches. The results were listed on the left hand side and were organized by genus and species names, so I did not know what families the various plants were in. The only thing for it was to look at images of each of the 37 plants until I found one that fit. My consolation was that 37 plants were a lot fewer than eight thousand!

I was about halfway through the list when I found a page from the Smithsonian Tropical Research Institute filled with copyrighted images that gave a satisfying match to my plant. It was identified as Odontadenia macrantha, a member of the Apocynaceae family.

Okay. As you know by now, I misled myself by those photographs, but at least I was in the right family.

So, to check the characteristics of the Apocynaceae, which have about 200 genera and about 2,000 species, which are particularly obvious in this plant. From wikipedia:

1. Leaves simple, usually opposite. Check.
2. Flowers usually showy and radially symmetrical. Check.
3. Stamens inserted inside the corolla tube. Check.
4. (from several other sources) Milky latex. Check

Fine. A member of the Apocynaceae, or dogbane, family. The roots of this family name, by the way, are, according to Dave’s botanary, Greek: apo, meaning away from or away with; kuon, meaning dog. The dogbane plant, an Apocynum species, is reputed to be poisonous to dogs.

This information on the toxicity of plants in Apocynaceae comes from kingsnake:

Many of these plants possess deadly toxins. However, they are notorious for being the larval food plant of a number of insects. Particularly, some sphynxid moths’ caterpillars incorporate the plants’ alkaloids to their own tissues, thus becoming toxic themselves. Several species of Plumeria are found in the Caribbean. They usually have large, colorful flowers with a sweet fragrance.

Many plants, however, produce toxins that are poisonous in high concentrations but may have medicinal benefits in lower doses. As the Encyclopedia Britannica points out:

Arrow poisons are obtained from many plants in the dogbane family, and the poisonous alkaloids of species belonging to the genera Strophanthus and Rauwolfia (qq.v.) also are used in medicines.

Indeed, a toxin from Odontadenia macrantha has been shown to be moderately toxic against A2780, the ovarian cancer cell line, according to an article published in Magnetic Resonance in Chemistry in 2003.

As to that error in identification, Dr. Foster explained to me that the Discover Life site just doesn’t have enough images to identify every specimen. The Mandevilla could have been among the 37 on my list, but it would not have had a picture to show what it looks like. If I’d had more patience, and stayed with that list of 37 until I had a picture (from elsewhere on the web) of every species on it, I would, I hope, have chosen the right species. Now I know I should have gone straight to Tropical Plant Guides and searched for the genus names there. Had I done so, I would have found this great image of Mandevilla hirsuta.

Dave’s Garden says that Mandevilla was named for Henry Mandeville,18th century British diplomat in Argentina; hirsuta means hairy, and, yes, the leaves are hairy.

Now, back to that sense of deja vu whenever I see the Mandevilla. Look again at the petals, their skewed shape and their flat and ruffled edges. I find that shape very appealing, and in reading up on Apocynaceae, I saw why it looked familiar. It reminds me, though faintly, of the frangipani, or Plumeria. The frangipani petals are also skewed and have essentially flat edges. They are more separate from each other, though, than are the petals of the Mandevilla and overall they have a much more elegant and sophisticated look. (This image is from a web site on St. John, US Virgin Islands).

Nevertheless, even if my deja vu was off base, I’m satisfied to think of the Mandevilla as a plebeian relative to the regal Plumeria.

It’s Tabebuia rosea, known commonly as the roble de sabana (oak of the savanna) or pink trumpet tree.

The pictures I took of the tree that is growing along our seasonal stream (here’s one, showing blooms on the lower branches and leaves on the upper)

don’t give the idea of breathtaking beauty that one can get from this tree, so I point you to an image at the at Smithsonian Tropical Research Institute site. There I learned that T. rosea is planted as an ornamental in almost all the parks in Panama.

But it’s the common name, roble de sabana, that caught my eye when I read about it. Why oak?

The genus Tabebuia is certainly not in the oak family, where the flowers are in the form of catkins rather than in the form of trumpets.

Tabebuia leaves (image below plus a better view at the link) look nothing like oak leaves;

the fruits look more like green beans than like acorns.

In fact, Tabebuia is a member of the Bignoniaceae, or catalpa, family. Thanks to Alwyn Gentry‘s book A Field Guide to the Families and Genera of Woody Plants of Northwest South America (Columbia, Ecuador, Peru), I know to think first of Bignoniaceae when I see opposite, compound leaves.

That’s as far down the checklist I needed to go in this case, because this tree is featured in nearly every tropical plant book I own, and I knew right away what it was from the pictures.

The genus name, Tabebuia, comes from the Brazilian Indian name for a species in the genus, and the species name, rosea, is pretty obvious from the color of the flowers – a pale to dark pink.

But, oak? Much of my information about this quality comes from the book by Willow Zuchowski, A Guide to Tropical Plants of Costa Rica. It comes from the high-quality wood of the tree, “…which is used in furniture and cabinets, tool handles, boats, yokes, interior finishing, and parquet.”

More interesting still is the information in The Plant-Book: A portable dictionary of the vascular plants, by D.J. Mabberley, describing the wood of other species of this genus. He says the wood is possibly the most durable American wood. Dead specimens of T. guayacan are still standing in the Panama Canal, and some 400-year-old beams in Panama are in excellent condition.

Strength and beauty.

At least one Brazilian species of Tabebuia, however, one with yellow rather than pink flowers, is being logged illegally in the Amazon for export, according to the Wikipedia entry on the genus.

By contrast, Zuchowski says that Tabebuia rosea was used in the Tree Trials Project in Costa Rica to test different kinds of trees that might be used to rehabilitate disturbed land.

Suddenly, I have a mission.

Our property is abandoned pastureland. We kept the trees that were growing here when we arrived. Now I know that we can plant more Tabebuia rosea trees without causing any harm and possibly, by doing so, we may help rehabilitate the land.

Strength, beauty, rehabilitation. Satisfying thought.

and large pods like this

(My Platonic Ideal Milkweed is shown in a copyrighted image here, under Asclepias syriacea.)

Imagine my surprise when a visiting botanist pointed out the “blood milkweed” – a delicate red and orange flower reminiscent of Latana (and more on that similarity another time) – in my own back yard.

With a botanist at hand, there was no problem identifying this plant: Asclepias curassavica, the tropical milkweed, of the family Asclepiadaceae. I will work up the characteristics of the plant that make it a member of the Asclepiadaceae shortly, but first a mention of the most famous relationship milkweed has with an insect – the Monarch butterfly.

I’ve drawn much of my information about this relationship from the Monarch Butterfly Fact Page. [25 Feb 2011 edit: A new resource for Monarch butterfly migration has come to my attention. It's a fine overview called "Facts on Migration."] Female Monarchs lay their eggs only on milkweed plants, attaching about 400 “clear green oval eggs” to the underside of a leaf. The caterpillars

emerge a few days later. In the United States, east of the Rocky Mountains, these caterpillars mature into butterflies so quickly that several generations will be produced in early to mid-summer. The generation that emerges in late August, though, will live eight or nine months and will migrate to Mexico. At the end of their life, the Monarchs will reach sexual maturity and will migrate back to the US, mating all along the migratory route.

No other butterfly in the world migrates like this. They often migrate to the same exact trees to which their ancestors (several generations ago) migrated last year.

Other than their spectacular migration behavior, Monarchs are known for being repulsive to predators. I remember a famous picture in a college textbook of a Blue Jay throwing up after having eaten a Monarch butterfly. The bright colors of the Monarch will help birds remember not to eat that butterfly again.

Now I’d like to look at the Milkweed Family, Asclepiaceae.* The family is named for the Asclepias genus, which in turn is named for Asklepios, the god of healing in Greek mythology. Milkweed roots have been used medicinally in the tropics for pain relief and for the treatment of scrofula.

The common name for the family, Milkweed, refers to the white latex mentioned earlier. This production in combination with simple opposite leaves with no teeth on their edges are good markers for the family.

The flowers, though, are unusual enough to make many members of the family recognizable on sight. As Elpel describes it, there are 5 separate sepals, 5 united petals, and a “corona” (like a crown) that looks like an extra set of petals. The corona consists of 5 hood-like forms facing toward the center of the flower. Inside the corona are 5 stamens fused to the ovary. In A. curassavica, the crowns are yellow and the petals are a red-orange color.

These flowers also have some features, which I’ll not describe, in common with orchids, although the two families are not related. (Note the ants in the image above. They are robbing nectar!) You can find excellent copyrighted illustrations that label of all these parts at Digital Flowers.

The fruit is that famous milkweed pod loved by children because silky threads are attached to the seeds inside. In this image, you can see a pod in front of the inflorescence, and a developing pod behind the inflorescence:

So my checklist for this family is: 1) simple opposite leaves with no teeth on their edges, 2) milky latex in stems, 3) complex flowers with crowns.

My final question is whether Monarchs like all flowers of the Asclepias genus equally or whether, the “common milkweed,” A. syriaca, is the Monarch’s favorite. Naturally, having grown up with the common milkweed, I assumed that was the best for the butterfly.

Luckily, I’m not the first to have had that thought. Some students from Willow Creek Middle School and Century High School in Rochester, MN, had a similar question. They went beyond my simple question, though. They raised 100 Monarch butterflies from eggs, 20 on each of 5 different species of Asclepias. They found that larvae fed on the tropical milkweed (A. curassavica) had the highest survival rate and the shortest time to pupation. The common milkweed was in the middle. So much for my provincialism!

What remains is for me to spot a Monarch on my plant, or even a Monarch migrating. It won’t be one that has migrated from the United States. Central American Monarchs migrate between the highlands and the lowlands only, and they migrate according to wet and dry seasons.

Ready when you are, Monarch!

—–

*Note on the milkweed “family”: I have chosen to use the old name, Asclepiaceae, for the family since much of the literature I cite uses that name. However, the Asclepiaceae no longer stand alone as a family, but have been placed within the larger family, Apocynaceae. The Apocynaceae include many more plants than milkweeds, and the milkweeds constitute the subfamily Asclepiadoideae.

It is a shrub with a candle-like flower-head or inflorescence. You can see in the next image its green bracts, which are tinged with yellow and orange, and its tubular, fuzzy, scarlet flowers.

The name, Aphelandra, comes from the Greek apheles, meaning simple, and andra, meaning male. The name could mean “sleek anther,” but it refers to the fact that the anther (the male, pollen-producing portion of the flower) consists of a single cell.

I’ll get back to that anther in a moment.

First, to continue the description.

Aphelandra is a genus in the family Acanthaceae, which consists of mostly tropical herbs, shrubs, or twining vines. The leaves are simple and opposite, with each pair of leaves at right angles to the pair below.

The flowers are usually arranged in an inflorescence which may be, like Aphelandra, a spike. The petals are usually tubular, and the fruit is a two-celled capsule which bursts open somewhat explosively.

The genus Aphelandra has 4 stamens; conspicuous and tightly overlapping bracts, and two-petaled flowers which are hummingbird pollinated. In the image below you can see glands on the bracts. These are extrafloral nectaries, which attract ants. The ants in turn protect the inflorescence and fruit.

This plant fits the description of Aphelandra scabra (as described in A Guide to the Tropical Plants of Costa Rica) except for one detail: the edges of the blades of A. scabra continue down the stems of the plant, according to the author.

I see no evidence of this characteristic in the plant at hand (see image of leaves). Neither can I see this characteristic in the image of A. scabra at the Smithsonian’s Trees, Shrubs, and Plants of Panama web site, so it’s most likely I’ve misinterpreted the author’s words. Nevertheless, I’ve been burned too often trying to apply a species name with insufficient data, so for now this Aphelandra shall remain Aphelandra sp.

Now for that big sex cell, the single-celled anther. Here’s one of the scarlet flowers, with the tip of its two tightly furled petals pulled off. The 4 stamens and slender stigma (barely visible) are tucked inside.

And here are the dissected parts of the flower. The stamens occur in pairs. One pair has been pulled apart. The other pair is wrapped around that slender stigma.

As a reminder, a stamen consists of the pollen-producing anther and a filament. The anther is that thick part at the end of the filament.

To understand why having an anther consisting of only one cell is amazing enough to name the genus after the feature, here’s a thumbnail image

and a link to an electron micrograph of a typical mature anther and its pollen, from the University of Sussex Centre for Advanced Microscopy. There are countless pollen cells in this single-celled anther!

If you do a Google image search for “anther,” you’ll find many more microscopic images of anthers, clearly delineating their many, many cells.

So far I’ve been unable to discover any discussion of Aphelandra‘s anthers, what are the implications of this uniqueness, or how many pollen grains a single cell can produce. It would be fascinating to learn.