Ramble Report September 8 2016

Today's Ramble was lead by Dale Hoyt.

Here's the link to Don's Facebook album for today's Ramble. (All the photos in this post, except where noted, are compliments of Don.)

Today's post was written by Dale Hoyt.

No. Attendees: 20

Announcements:

Sue called everyone's attention to an article about Bob and his new poetry book in last week's Flagpole (August 31).

Weds., Sept. 14, 7-8:30PM; An Evening of Poetry and Nature @ Russell Special Collections Library. Free parking at Hull St. Deck next to the Library. An evening of local authors celebrating poetry and nature hosted by UGA Friends of the Georgia Museum of Natural History. Reading their poems will be: Philip Lee Williams, Clela Reed, Robert Ambrose, Jr. and retired Ecology professor John Pickering.

Today's readings: Sue read a piece on sleeping in trees and all that it entails, from the NY Times Sunday magazine section.

Dale read the first paragraph from Weds. (9/7/16) NY Times OpEd by Thomas L. Friedman, We are all Noah Now.

Today's route: From the parking lot we took the mulched trail and turned left on the White trail; White trail to the Orange Spur trail; left on the Orange Spur trail to the Orange trail; right on the Orange trail to the power line; right on the power line to the road; right on the road, returning to the parking lot.

Skeletal remains of White-tailed deer

On the Orange Spur trail we were startled to find the skeletal remains of a female White-tailed deer. We knew that the deer was a doe because the skull lacked the pedicels that mark the location of the antlers in male deer. (Male deer shed their antlers and grow them anew each year.) Missing from the skeleton were the limbs and lower jaw but the vertebral column was nearly complete. The absence of the limbs suggests that a predator, perhaps a coyote, or scavenger carried them off. Jeff, who lives in Oglethorpe Co., told us that deer were now much less common on his property and that their absence correlated with an increase in the number of coyotes that he has heard howling at night.

Wingstem, alternate leaf arrangement (photo by DH)
(also notice the wings on the stem)

Southern Crownbeard, opposite leaf arrangement (photo by DH)
(also notice the wings on the stem)

Nearby was a Wingstem, an example of a plant with alternate leaf arrangement. You may recall that there are two principal ways that plants have their leaves arranged on the stem: alternate and opposite. With opposite leaves you find that the leaves are paired, one on each side of the stem. (The place where the leaves emerge from the stem is called a node.) Going up the stem to the next node the pair of leaves are shifted 90 degrees relative to the leaves at the node below.

The Golden Angle
(source: Wikipedia)

The alternate leaf arrangement has only one leaf per node and the leaf at the next node is shifted in position 137.5 degrees. This angle, known as the Golden Angle, leads to the minimal overlap of leaves, so the upper leaves of the plant shade the lower leaves to the least extent possible. The diagram above shows the angle at which the length of the red portion of the circumference (b) divided by the length of blue portion of the circumference (a) is the same as the length of curve a divided by the circumference of the whole circle: (b/a = a/(a+b). (The Golden Angle is related to the Golden Ratio, which is the ratio of the two parts of a line segment divided so that the ratio of the smaller part to the larger part is equal to the ratio of the larger part to the whole line segment. It is said that the navel of the human body is located at the point where it divides the body into the Golden Ratio. (1.618 = The Golden Ratio.) 

Ant attacking a tiny, cryptically colored caterpillar on a Wingstem flower.

While we were focused on alternate vs. opposite leaf arrangement Don found a tiny caterpillar being attacked by an ant on the flower head of a Wingstem. This dramatically shows why so many plants have ant-attracting extra-floral nectaries. We've seen two such plants on previous rambles: the Maryland Senna and Purple Passionflower. The ants are attracted to such plants and in the course of searching for nectar they happily devour anything that contains protein.

Is everything adaptive? A Rambler asked a question: "What are the wings on a Wingstem good for?" (Or maybe the question was "Why does a Wingstem have wings?") Questions like these have for many years divided biologists into a couple of different camps, the Adaptationists and the Neutralists. Like all such divisions these do not capture all the nuances of different opinions, but they are useful in getting at the essence of different positions. The Adaptationists maintain that all features of living organisms are adapted to their environment. Their research program is focused on figuring out what features are adaptations and what aspects of the environment they are adaptations to. The Neutralists accuse the Adaptationists of creating "Just So" stories. (The Just So stories were written by Rudyard Kipling for children. Each story told how different features of animals came to be; e.g., How the Elephant Got his Trunk, How the Camel got his Hump, etc.) The Adaptationists are charged with devising explanations without testing them, or, even worse, non-testable explanations. Neutralists think that some characteristics have no effect on an organisms survival or reproduction. In other words, that some features are adaptively neutral and, as such, they are invisible to natural selection. Neutral theory has shown that small differences in adaptation can be overwhelmed by chance events in small populations. How these differences will play out is for the future to decide.

But back to initial question: why do Wingstems have wings? I do not know of any adaptive explanation for the presence of wings. Perhaps they are the side product of some developmental process that is important to the plant. Which is another way of saying that they are not, in themselves, adaptations, but are byproducts of some process that is adaptive. But I should emphasize that I don't know any way of testing that hypothesis.

Oyster mushrooms on log

Turkey Tail mushrooms on small stump.

This section of the trail passes through an area with lots of fallen trees, most of which support large numbers of mushrooms growing on the dead wood. When you see a mushroom you need to remember that you are looking at the fungal equivalent of a flower. It is only a small part of the fungus. The body of the fungus lies out of our sight – it is a network of microscopic threads, called a mycelium, that lives in the soil or wood, actively digesting the organic material. In other words, the mycelium is rotting the wood.

There at several types of wood-rotting mushrooms. Two of the commonest are called white rots and brown rots, named for the color of the wood that remains after they have done their work. What we call wood is the structural material of trees and is made of the cells of the trees. Plant (and tree) cells are surrounded by a wall made largely of cellulose, the material that paper is made of (paper being made from wood pulp). By itself cellulose is not particularly strong and if it were the only thing plant cell walls were made of, plants would never be able to grow to the heights of tree. But trees produce a substance, lignin, that stiffens and strengthens the cellulose in the cell walls. It is the combination of lignin and cellulose that allows trees to grow to such great heights.

But back to the rots. Lignin is brown in color and cellulose is white in color. So a mushroom that digests the cellulose leaves behind the brown lignin and one that digests lignin leaves behind the white cellulose cell walls.

The Turkeytail and Oyster mushrooms we saw today are both white rotting mushrooms – they digest the lignin and leave the lighter cellulose behind.

The soil in the flood plain is very sandy and the presence of all this sand tells us that the river is constantly moving about, depositing sandy material on one side and carrying it away on the other. Also, when it floods, the flood waters that carry material from upstream slow down and spread over the flood plain. This decrease in velocity causes the heavier material, like sand grains, to fall out of the water, gradually building up the natural levy on each side of the river. As a result the flood plain gets sandier as you cross it toward the river. The finer organic material is lighter than the sand and is carried further across the flood plain before it, too, settles out.This makes the flood plain very rich in nutrients and produces luxuriant plant growth. (The downside is that it can also carry pollutants from upstream and deposit them in downstream flood plains.)

Asiatic Dayflower; two blue petals; one tiny white petal

Virginia Dayflower; three blue petals

On the Orange trail there is an abundance of plants growing where the Privet was removed. One that I'd like to mention is the Virginia Dayflower, because it is so similar to a non-native, the Asiatic Dayflower. You've probably seen the Asiatic species growing in your yard, around the foundation or next to the driveway. It has two prominent blue petals and one very tiny white petal. The native species, Virginia Dayflower has three equal sized blue petals. Compare the photographs above and you'll see the difference.

Carolina mantis female

Praying Mantis: Late summer is when we begin to find the Praying mantises on our rambles. Previously we've seen very small mantis nymphs and one large female Chinese mantis. Today Tom sighted a small, but sexually mature female mantis. After consulting various references I'm pretty certain that this is one of our native mantises, the Carolina mantis. It is small, about 1/2 the size of the Chinese mantis and has a greatly swollen abdomen, indicating that it has a lot of maturing eggs inside. Another indicator of its adult status: it has wings. Mantises have direct development; when the egg hatches a tiny, tiny but recognizable Praying mantis emerges. At this stage it has only tiny wing buds. It will grow in size and moult its exoskeleton several more times, each time the wing buds get a little larger, but they remain non-functional until after the last moult. The mantis we found today has fully developed wings, but the female Carolina mantis does not fly, only the male of species does.

Yellow Bear; caterpillar of Virginian Tiger Moth

Gulf Fritillary caterpillar

White-marked Tussock Moth caterpillar

Caterpillars: We were fortunate to see several different caterpillars today. The first was covered with dense yellowish hairs and is probably a Yellow Bear, the larval stage of the Virginian Tiger Moth. The second caterpillar was truly spectacular – the caterpillar of the White-marked tussock moth. It almost looks unreal. The caterpillar feeds on a wide variety of plants, unlike the next caterpillar, that of the Gulf Fritillary butterfly. We saw these caterpillars last week feeding on the Passionvine on the deer fence. This week they had nearly denuded the leaves on a large section of the vine and most of them were approaching the size when they pupate.

Cloudless Sulphur chrysalis; look for the silk loop attached to the leaf directly above the chrysalis.

Gulf Fritillary chrysalis

Chrysalids: Along the fence we found three chrysalids of the Gulf Fritillary. But the big surprise was the discovery by Paige of the chrysalis of the Cloudless Sulphur butterfly. This beautiful green and pink looks for all the world like a leaf and how Paige spotted it is a wonder. Another interesting point: look closely at Don's photograph and you will see a fine, silken line descending from the leaf above the chrysalis. This is actually a girdling line of silk that is spun by the caterpillar. The chrysalis is attached to the stem at the tip of its abdomen and is hanging in the silk loop spun when it was a caterpillar. The Swallowtail butterflies also suspend their chrysalises in the same manner. The adult butterflies will emerge after developing 1 to 2 weeks inside the chrysalis.

Photographs of the many other plants that we saw today can be found on Don's Facebook album (link at the top of this post.) The complete list of species observed follows:

SUMMARY OF OBSERVED SPECIES:

Common Name	Scientific Name
White-tail deer (skeleton)	Odocoileus virginianus
Wingstem	Verbesina alternifolia
Silverbell tree	Halesia carolina
Turkey tail mushroom	Trametes versicolor
Oyster mushrooms	Pleurotus ostreatus
American pokeweed	Phytolacca americana
Late flowering thoroughwort	Eupatorium serotinum
Camphorweed	Pluchea odorata
Virginia dayflower	Commelina virginica
Climbing hempvine	Mikania scandens
Bur cucumber	Sicyos angulatus
Pennsylvania smartweed	Polygonum pennsylvanicum
Tiger moth family, caterpillar	Family Arctiinae
Carolina mantis	Stagmomantis carolina
Catbrier	Smilax sp.
Spoted jewelweed	Impatiens capensis
Tall ironweed	Vernonia gigantea
Sweet autumn clematis	Clematis terniflora
Leafy elephant's foot	Elephantopus carolinianus
Climbing buckwheat	Fallopia scandens
Silvery checkerspot butterfly	Chlosyne nycteis
Wild potato vine	Ipomoea pandurata
Small white morning glory	Ipomoea lacunosa
Cloudless sulphur butterfly (chrysalis)	Phoebis sennae
Sheetweb spider webs	Family Linyphiidae
Mild waterpepper	Persicaria hydropiperoides
Virginia/smooth buttonweed	Diodia virginianum
Maryland senna/Wild senna	Senna marilandica
Arrowleaf tearthumb	Persicaria sagittata
Woodland sunflower	Helianthus divaricatus
Hairy sunflower	Helianthus hirsutus
Common Camphorweed	Heterotheca latifolia
White marked tussock moth caterpillar	Orgyia leucostigma
Gulf fritillary (caterpillar and chrysalis)	Agraulis vanillae