Thursday, July 18, 2013

July 18, 2013, Ramble Report

 by Dale Hoyt

We had a group of 9 today. Hugh started us off by reading a few passages discussing some of the problems Darwin encountered in his study of barnacles. They are from Carol Kaesuk Yoon's book, Naming Nature: The Clash Between Instinct and Science, pp. 70-71:

"I have been struck," he [Darwin] wrote to Hooker, "with the variability of every part in some slight degree of every species:  when the same organ is rigorously compared in many individuals  I always find some slight variability, & consequently diagnosis of species from minute differences is always dangerous."
. . .

The variation he had been searching for, hoping to find.  For in an evolutionary view of life, variation is not only real, it's essential, critical, and exactly to the point.
. . .

But as he noted, while "pleasant to me as a speculatist," this variation was "odious to me as a systematist."  In fact, "Systematic work would be easy were it not for this confounded variation…"  It was the understatement of the (nineteenth) century.

As soon as a person sees life through an evolutionist's eyes, as soon as they see all that confounded variation, all that incipient evolutionary change, their view of the species changes as well  It is not merely mutable; it is ever-changing.  What we see at any moment, we realize, is just a snapshot in time, a moment in the great flux of the long life of its lineage, on its way to diverging into new species.  It's a triumph when this happens, for you have gained great evolutionary insight.  The only problem is now you will have absolutely no idea how to order the living world.  You will have no idea how to decide what constitutes or doesn't constitute a species.  You won't have a clue as to how to decide where one variety, one species ends and another begins.  And that was Darwin's problem [with barnacles].

Terry brought a fold-out pamphlet with pictures of common butterflies found in our area (Butterflies of North Carolina, South Carolina and Georgia: Common and Notable Species by Mark Minno). This looks like a handy reference to carry with you when you're out and about.
We covered the same ground as last week's walk: White trail from the parking lot to the power line, then down to the river and back up the powerline and through the Dunson Garden (to avoid the sun). Here's what we saw along the way:
The Cinnabar Chanterelle mushrooms were still present in abundance, shining like glowing orange flags on the wet, shaded forest floor. It's hard to keep in mind that mushrooms are the "flowers" of a more extensive fungal body that consists of fine threads permeating the soil and, in some cases, enveloping the roots of trees and other plants. We looked for evidence of insect feeding damage on the Chanterelles and found none. This is a mystery to me because when I took a mushroom course at UGA 10 years ago every Chanterelle we found was crawling with fly larvae. That was in late August, early September and a different kind of Chanterelle. On one of the other kinds of mushrooms we found there were a number of fungus beetles, but no fly maggots.

Growing on various fallen tree limbs we found Turkeytail fungi as well as False Turkeytail. (The true Turkeytail has a smooth undersurface whereas the "Not-A-Turkeytail" type have porous under surfaces.

Among the other mushrooms we think we were able to identify were Caesar's Amanita and Berkeley's Polypore (Bondarzewia berkeleyi).

Out in the power line we found a Horse Nettle (Solanum carolinense) in bloom. This plant is in the nightshade family (Solanaceae); other familiar members of this family are tomatoes, potatoes, and eggplant. Many of these solanaceous plants have the same unusual arrangement of the anthers. They are bright yellow and are clustered like a tent around the pistil. The anthers are further unusual in that they do not split open to release their pollen. Instead there is a pore at the end of each anther from which the pollen can emerge. But the flower must be shaken or vibrated to remove the pollen. To get this pollen the bee must engage in "buzz" pollination. It grips the flower with its mandible, curls it body over the anthers and makes a buzzing vibration that shakes out the pollen. The vibration is produced by the flight muscles contracting without causing the wings to move. The pollen is attracted to the bee's furry body because of a difference in electrical charge that is built up as the bee flies, just as you build up static electricity when you shuffle across a rug. The flower and its pollen are negatively charged, the bee carries a positive charge.

Here is a link to a site that has a lot of information about buzz pollination, as well as several videos of bumblebees doing it. Buzz pollination videos.

Another cool thing: there is evidence that bees can determine when a flower has been previously visited. A bee visiting a flower will "discharge" it and subsequent bee visitors can detect the diminished charge, probably because some of their sensory hairs are not as strongly attracted to the bloom.

Avis spotted an Indigo Bunting in the trees and it cooperated by remaining there long enough for everyone to view it through Emily's binoculars. The iridescent blue of the male bird is always breathtaking!

We reviewed the structure of the Passion flower (Passiflora incarnata) flower and how it is pollinated, principally by the large Carpenter Bee (Xylocopa virginiana). Also how each flower can be either hermaphroditic or unisexual male. This condition is apparently determined by how much energy is available to each individual flower; those with adequate supplies become hermaphroditic while those with less energy available become functionally pollen donators only. This is done by lowering the three stigmas to a level where they can be pollinated in the bisexual flowers or allowing them to remain in an upright position where they will never receive pollen ("male" flowers). The decision is made by each flower individually, so one plant can bear each type of flower.

Passionflowers have extra-floral nectaries, a pair of glands at the base of each leaf blade that secrete nectar. This source of sugar is attractive to ants and the ants that patrol plant, looking for nectar and protect the plant by also eating herbivores like small caterpillars that they encounter.

We also saw two beetle species are are associated with passionflowers. One was a bright orange and black. This type of conspicuous coloration is typically associated with either distastefulness or poisonousness; i.e., it's a warning coloration. The passionflower vine contains several compounds that are toxic and/or distasteful. Some of the animals that eat the plant store these chemicals in their body and become toxic or distasteful in turn. (The monarch butterfly has a similar relationship with milkweed plants.)

We saw a single Pearl Crescent; this is a very common and very pretty butterfly. Its larval food plant is various species of asters.

Hugh kept scanning the "Wingstem jungle" under the power line for Goldenrod. It's hard to find it among all the other green stems in the jungle but he did locate a couple of plants that had galls. These particular galls are probably caused by a fly (family Cecidiomyidae for the entomology nerds) that lays an egg in the growing tip of the plant. The plant reacts by producing shorter internodes, so the leaves all bunch together at the growing tip. The larva of the fly feeds on the plant tissues inside the bunched leaves. We've been looking for the gall-forming fly that produces a spherical gall on the stem, but haven't yet seen one in the Garden although we have spotted some around Lake Herrick on the UGA campus.

We also found Wild Senna (Senna marilandica) plants where we first located them last year. They are not yet blooming. Joan also noticed that these plants have extra-floral nectaries!

Many of the same plants that were in flower last week were observed again: Virginia buttonweed, Pokeweed, Wood Sage. Not flowering, but abundant were the Wingstems and the Ironweed. We heard Green Frogs (Rana clamitans) calling and saw two Green Tree fogs (Hyla cinerea), one newly metamorphosed. A new plant in flower was a Red Morning Glory (Ipomea coccinea) clambering up the fence near the gate. On the hillside near the Dunson Garden a Mullein was still in bloom.

It was beginning to get hot so we decided to walk back through the shady Dunson Garden and observed the Hibiscus in bloom. Hugh also discovered a Golden Garden Spider orb web in the Hibiscus. Also seen: newly metamorphosed Spadefoot toad, Royal Fern, Jack-in-the-Pulpit with developing fruits, Clethra in bloom, Rattlesnake Master and a Yellow Wood tree.

While in the Dunson Garden we came across a Black Cohosh that was still blooming. Its tall inflorescence still had a few flowers at the very tip. This prompted Carol to tell us about determinate and indeterminate growth forms. The Cohosh exhibits an indeterminate growth form -- the terminal bud of the flowering stalk continues to grow and new flowers appear from lateral buds below the terminal. The first of these flower bud are the oldest and they open first. Then successive buds higher up the stalk open until the top is reached. Because the flowering stalk can continue to grow and produce more flowers the number of flowers that will ultimately be formed is indeterminate. As good discussion of the kinds of inflorescence and growth forms in flowering plants can be found in this Wikipedia article.

We then adjourned to Donderos' for our usual snacks and conversation.


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