Forest thinning

My goodness, I’ve been going back through my old data sets from the 2006 and 2007 season when we studied the effects of forest thinning on many aspects of the ecology, including the invertebrates, which, to me, suggests moths. Look at these graphs, for example. Each of them considers a single group, or genus, of moths as they respond to thinning across the years. The leftmost points are from the control stand–never thinned. The next point, moving right, is a collection made from a stand thinned the previous year. The highest points are collections made four years after the thinning. And the last point, way off to the right, is a collection made sixteen years after thinning. Look at the pattern.screen-shot-2017-01-09-at-8-16-10-pm

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Can you see the trend in all of these groups? The upshot is that they all show reduced numbers after one year of thinning, then they all show increasing numbers after four years. Then, by sixteen years after thinning, the numbers fall to near the original set. The bottom graph shows the overall biodiversity of ALL moths in this study. But the wonder of wonders is that, while the biodiversity is about the same after sixteen years, the community has greatly changed. That is, many of the original species are gone, but have been replaced by a new set. So biodiversity is not affected, but the community structure is very, very different. All this to be published in the next year. One of my 2017 goals. Questions? Ask.

Butterfly and Moth Biodiversity

Do you have any idea how many moth species live in the Pikes Peak Region? Take a guess. A hundred? A thousand? Ten thousand? Well, it turns out, if you have data like I have, a reasonable estimate can be made. I used the Clench equation, taken from Harry K. Clench’s paper* on estimating butterfly biodiversity on reserves. It is useful after a few years (or hours) of data points are available. If you want the answer, you can skip the math and go to the case study, below. But in case you’re interested…

The equation shows that the eventual number of species (Se) in a locality can be estimated as a function of a constant, K, and the number of hours spent in the field (N).

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As K approaches zero, N + K approaches N, and Se = S. In this equation, S represents the number of species taken at any given time and N represents the number of years (or hours) afield. Simplified, the equation looks like this:

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Data that show a positive curve will not apply, of course. This can result if the first expedition is poor but the second is extraordinary. But as more data accumulate, a negative curve is generated, and any two points roughly on the curve can be used to estimate the asymptote, which is equivalent to Se.

Let us assume that after two years, 62 species have been cataloged (2, 62), and that after an additional 2 years, a total of 81 have been recorded (4, 81). Using these to create a system of equations allows us to calculate K, and then Se, as follows.

2Se = (2)(62) + 62K

4Se = (4)(81) + 81K

multiplying the first equation by –2 yields this pair:

– 4Se = –248 – 124K

4Se =   324 + 81K

eliminating the Se term,

0 = 76 – 43K

– 76 = –43K

K = 1.77

Substituting into the original equation yields an estimate of

Se = 124 + 110 = 234 species

A CASE STUDY:  MOTH BIODIVERSITY IN THE PIKES PEAK REGION

screen-shot-2017-01-14-at-1-20-43-pm*Clench, H. K. 1979 How to make regional lists of butterflies: some thoughts. Journ. Lepid Soc 33(4) 216-231

 

Moths and Flowers

Litocala sexsignata on Salix fls.Lycomorpha grotei on Rhus fls.

Above, a Litocala sexsignata moth on willow flowers; A Lycomorpha grotei moth on sumac flowers.

Almost everyone has the butterfly/flower thing down, although many people don’t realize that butterflies are not good pollinators. Generally, their long legs keep them far above or away from the stamens, which carry pollen, and their long probosces reach delicately through the reproductive parts to extract nectar. Butterflies, generally, are nectar thieves.

It might come as a surprise that moths are similar, but most tend to visit flowers at night. Not all moths feed as adults, but many of those that do are also poor pollinators, for the same reason that butterflies are. And lots of moths are diurnal–let’s keep in mind that butterflies and moths are not really different. Butterflies form a set of Lepidopterans that have adapted to living during the daylight, and therefore use color and pattern more than most moths do. Otherwise they’re just day-moths. But several families of moths are diurnal, and especially at high altitudes where the nights are very cold. Here are a few moths visiting flowers during the day.

Eriplatymetra coloradensissyngrapha

An Eriplatymetra coloradensis moth on Monarda flowers; Syngrapha angulidens moths on nodding thistles. Note that in scientific nomenclature, Latin names are italicized, as they are foreign words. Also, the genus name is always capitalized, while the species name is never capitalized. All this to make Karl Linné feel better.

Moth Porn

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Try to imagine being a moth, just hatching from your cocoon. I’ll give you a minute… Crawling out of the silk. Dragging your wet body up a tiny grass stem. Are you there? Okay, you are a male. You don’t know anything, and you can’t think anything, although those two conditions are not causal. I mean, it’s not because you are male that you are mindless. A female would be in the same condition, intellect-wise. Whatever. You’re a male moth, but, having no mind, you don’t know what it means to be a male. You don’t even know you’re a male, but I’m telling you. Imagine it. Male moth.

One thing you can do is detect signals from your environment, both internal and external. From the outside you pick up a scent with your antennae, a little buzz, or a tiny shiver of “yes.” You try to flap your wings because you can’t imagine doing anything else, but they don’t work. They’re still wet, hanging off your back. So…

A half hour passes, during which you don’t do anything except crawl a few inches higher on the dead grass stem that you touched with your little tarsi, your toes, and try to move those limp rags—the only parts of you that seem important, besides your antennae, which still buzz a little.

It is dark, which you recognize as different from light. But it doesn’t mean anything. It’s just dark.

After a time, your wings dry and you are able to fly. You don’t know why, because your brain has no logical functions. But what else is there to do? It’s pretty different from the limitations of the caterpillar. But you have forgotten that.

As you fly aimlessly about, you once again notice the little “yes” signal from your antennae, so you begin to fly a zigzag pattern upwind. Why upwind? Because that is where the signal seems to increase, and you are driven to increase this little “yes” feeling. It’s good.

But what is this mysterious scent that draws you inexorably forward into the night? You don’t know, because you are ignorant of everything but sensations and compulsions. But you keep at it, back and forth, always upwind, as long as the signal increases.

And then the scent disappears. Damn. You had only one thing in the world that motivated you, and it vanished like a change in the wind. You would think, “Stupid world!” if you could think. But you can’t.

Of course, it was a change in the wind. So you’re left mindlessly—I mean, seriously mindlessly—flying around with no destination in mind, because you have no mind. I can’t stress strongly enough how dumb you are. Just pathetically moronic, with no explanation except that with a brain that small, how smart could you possibly be? It’s not an insult, it’s just a fact. Even if you tried to think a thought, you’d fail. You have nothing.

But wait! There’s that luscious signal again, on the breeze. You resume your mindless quest to find enhancement of that happy message. You have no memory of having forgotten it. You just go for it. And it gets better.

Finally, when the signal is so strong that it threatens to explode your tiny brain, you bash clumsily into—another moth! “OMG!” you would think, if you could think, “I’m not the only creature in existence?” No, dummy, there’s another, just like you, with similar wings but, oh, my goodness, she’s not exactly like you! And this scent signal has you turned on like a freaking mercury vapor arc lamp, and she seems completely receptive to your sudden desire to… Wha–?

Well, here’s an interesting little factoid. Insect genitalia are pretty different from ours. In fact, ours are sad little features that I might characterize as a post and a post hole. But with moths, the male parts have claspers (what if she tries to fly away?), prongs, brushes, hooks and barbs—a whole assembly of details that makes sure that this female has the right species fit. For her part, the vaginal canal has expanded balloons and spines and long twisted loops—a whole assembly of details that makes sure that this male has the right fit. It’s a lock and key arrangement. It’s how they avoid hybridizing, and how we identify most similar-looking moth species.

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Okay? So by now, you’ve made your entrance and you have to work it around corners and hoops and into crannies, and when it all feels just right, you start to work up a reproductive package. This involves pushing a long, clumsy spermatophore through your own convoluted system into her complex bursa copulatrix This is not easy.

Several hours later…

When the sun comes up, you are a mess. The signal is gone, she is gone, and you’ve got the sun blazing down on your face like a blowtorch. Then an enormous sparrow roars into the scene and grabs you in its beak and holds your wings down with its talons to rip them off, and mashes your tiny body a few times, and your last sensation is the dark throat and crop of this destroyer as you blink out. If you could think, which you can’t, you would think, “Ha ha! You ignorant, blundering predator! You’re too late! I already did it!” Life is good.

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