Tuesday, April 21, 2015

Ramble Report April 16 2015

This post was written Dale Hoyt. The photos are by Don Hunter; more photos from this ramble are here.

Sixteen people braved the chilly (for April) weather this morning and we had a wonderful time.

Today's reading:
Emily read a poem, Letter to the Sun, by Joyce Sidman, from Butterfly Eyes and other Secrets of the Meadow, 2006, Houghton Mifflin. It was perfectly appropriate after two overcast, chilly days in the middle of April.

Dear Sun:
It's so wet.

The meadow has turned to bog.
Chill, sinking, squishy sog.

We long for your face, Sun.
We crave your rays,
                                honey-colored days.

O Dear Sun,
we're huddled in our buds,
waiting to bloom.

Please come soon . . .
the only ones still singing
are the frogs.


Today’s route:  All the trails in the natural areas were very muddy so we went down the walkway in the Shade Garden, and took the White trail mulched path at the end of the second hairpin bend. Instead of continuing on the White trail we turned right and followed the mulched path to the upper Dunson Native Flora Garden.  We weaved our way through the DNFG, past the yuccas, and across the power line ROW, to a large patch of flowering butterweed. We then retraced our steps, heading back to the arbor and Donderos'.

Before starting off I passed around a living female Luna moth that had laid a few eggs Wednesday night. I also passed out a mini-book of seven common ferns that can be found on the Orange trail. Ed told us about a pair of foxes with four kits that live in his neighborhood – they were pretty noisy for much of the night.

Shade Garden:

On the way down the walkway we noted that the Piedmont azalea was still blooming, but many flowers had been beaten off by the rains. At the first hairpin there was a Pale yellow trillium in bloom, far from its probable source in the Dunson Garden.

Dunson Native Flora Garden:

Wild Gingers:  We found two kinds of Wild ginger in the DNFG: Canadian wild ginger
Canadian wild ginger
(CWG) and Little brown jug (LBJ), also called Heartleaf wild ginger. Both are quite distinctive: CWG loses its leaves
Little brown jug
during the winter while LBJ retains theirs; CWG leaves are kidney-shaped, about as long as they are broad, while LBJ leaves are much longer than broad. LBJ leaves are also mottled with lighter green spots. CWG leaves are found all over the garden this spring, so it has been quite successful. Does anyone remember seeing this many last spring?

The flowers of both species are found under the leaf litter;
Canadian wild ginger flower bud
those of LBJ resemble little brown jugs, hence the common name. CWG flowers are a similar shape but they are fuzzy and when they open the sepal lobes are red and elongated. The CWG flower that we found had a barely open bud.

Why would any plant bury its flowers in the leaf litter? Flowers are supposed to attract pollinators like bees, flies, butterflies or moths. Hiding the flower under dead leaves would seem a poor strategy for attracting pollinators. 

How do we discover what pollinates a flower? Normally you sit and watch, but that strategy fails when the flower is out of sight. If you remove the litter so that you can see the flowers you disturb the area so much that the normal pollinators, whatever they are, may not appear. So people who have investigated this question have resorted to indirect methods. They have enclosed the plants or just the flowers in cages that exclude insects to see if seeds are still produced. In the case of Wild gingers, caged plants do produce seeds, but not as many as uncaged plants. This indicates that these flowers are capable of self-pollination, but that more seed can be produced when pollinators are have access to the flowers. The actual pollinators remain unknown for our two Wild gingers. But possible candidates are ants, beetles or fungus gnats.

One thing that burying the flower in the leaf litter does accomplish is to make access to the seeds easy. Like many other spring ephemerals, both CWG and LBJ produce seeds with elaiosomes, an oil-rich structure attached to the seed. Because the elaiosome is so energy-rich it is greatly desired as food by ants. They carry seeds back to their nests and remove the elaiosome to feed their young. The seed itself is discarded. But the ants have carried it some distance from the parent plant, dispersing the seed into new areas.

Pale yellow trillium
Trilliums: They are still in bloom in the garden, dominated by the Pale yellow trillium that seems to be everywhere. There are smaller numbers of Chattahoochee trillium and Sweet Betsy trillium still with flowers. Like the Wild gingers, the Trilliums have seeds with elaiosomes ("EE_L) , accounting for their wide dispersal around the garden. But it is a mystery to me why the Pale yellow trillium should be so much more successful in spreading.

Christmas fern developing fertile frond tips
Southern lady fern
Today was Fern heaven in the DNFG – are coming up everywhere! The list of
Rattlesnake fern with fertile frond

species we encountered is long: Sensitive fern, Rattlesnake fern, Northern Maidenhair fern, Hay-scented fern, Southern Lady fern, New York fern, Cinnamon fern and, of course, the omnipresent Christmas fern. Some of these are
Cinnamon fern with fertile fronds
beginning to develop fertile fronds, so called because spores are produced on these plant parts. In some ferns every frond can be fertile but in others the fertile parts are restricted to parts of a normal frond or to a separate, specialized frond. In the Christmas fern only the terminal 1/3 of some of the fronds produces spores. This portion of the frond is narrower and the leaflets are distinctly smaller. The Christmas fern we observed was just beginning to develop sporangia (the structures that produce spores). In this fern the sporangia are grouped together into sori. Right now the sori look like little pale bumps on the undersurface of the pinnae (a botanical name for fern leaflets). As they mature they will become a dark, rusty brown. Other ferns, like the Cinnamon, Rattlesnake and Sensitive ferns have separate fertile fronds that are not leafy and bear only sporangia. The sterile fronds do not bear sporangia. We only saw one Cinnamon fern off to one side of the DNFG near the road. The fertile frond that gives the fern its name is not yet mature – when it is it will be a rich umber color, just like cinnamon.

The number of spores produced by a single plant is prodigious – billions of spores. They are so small that as they are released even tiny air currents can carry them off. Ultimately, like dust, they fall onto surfaces: rotting logs, rocks, leaf litter and exposed soil. If where they land is suitable, like a moist, shady place with good soil, the spore will germinate. But it doesn't look like a fern. It looks like a strand of algae. It grows into a flat green structure about the size of your little finger nail. This structure develops reproductive structures that produce egg and sperm cells. If water is present the sperm cells swim over to the egg cell and fertilize it. From this fertilized egg develops the plant we recognize as a fern.

The difference between a spore and a seed?

The difference is both functional and genetic/developmental.

A spore is a single cell and has very little nutritive material stored in it. After germination it grows into a multicellular organism without sexual fusion with any other cell.

A seed is a reproductive unit found in flowering plants, conifers, ginkgos and cycads. It is the result of sexual fusion and contains a multicellular embryo plus tissues that store nutrients that will support the growth of the embryonic plant. (Exceptions: some plants can produce seeds without a sexual process – a process called parthenogenesis. The Dandelion is an example. Orchids produce seeds without stored nutrients.)

Because spores contain very little in the way of stored nutrients a germinating spore must be capable of feeding itself in order to grow. The spores of ferns and mosses contain chloroplasts that perform this function in the presence of sunlight.

Genetically, spores have only half the genetic material found in the cells of their parent plant. This requires a special kind of cell division, called meiosis ("my-Oh-sis"), that reduces the number of chromosomes in the resulting cells. In animals this type of cell division occurs only in the sex organs, the testes or ovaries, and meiosis produces either sperm cells or egg cells. The sperm and egg fuse with one another to produce a new organism that has the same amount of genetic material as its parents. In flowering plants meiosis occurs in the cells of the anthers and ovaries.

Other plants in the DNFG

Blooming plants: Wild Columbine, Solomon's Seal, Jack-in-the-Pulpit; Solomon's Plume, Atamasco lily, May apple, Virginia spiderwort, Green and Gold, Violet wood sorrel, Shooting stars, Painted Buckeye
Atamasco lily

Plants not yet in flower: Black Cohosh, Northern Horse Balm, Green violet.

Plants past flowering: Perfoliate bellwort (with developing fruit), Golden ragwort already producing seed, Goldenseal.
Perfoliate bellwort fruit 

Beyond DNFG/ROW:

In the paths and mowed places we found the small, weedy plants typical of this season: Beaked corn salad, Lyre leaf sage, Field madder, Hop clover, Purple dead nettle and Carolina geranium. The clover and the dead nettle are non-natives that have become naturalized; the others are native species. All of these are typical of disturbed areas and seldom found in other habitats.

The reason for going to this part of the garden this morning was to see another species of ragwort, Butterweed, that has just started to bloom. There is a large stand of this flood plain species growing in the pines to the east of the power line. It is a ragwort (genus Packera) and, like the other species in that genus, has numerous cheerful yellow flower heads. It can be distinguished from Golden ragwort, the other Packera species we have seen this year, in several ways: 1) it has a thick, hollow stem with a purple stripe; 2) It has more flower heads; 3) it is found in very wet or moist areas – especially flood plains. There were many others growing closer to the river and Lee reported that he had seen the same species on the White trail by the river.
White-crossed seed bugs mating (male on left)
While we were examining the Butterweed flowers Sandra found some interesting insects: a mating pair of White-crossed seed bugs (hereafter, WXB). These are true bugs, members of the bug family Lygaeidae, that feed on the seeds of plants. You might have seen another member of this family: the Milkweed bug that feeds on milkweed seeds. Both bugs are strikingly colored in black and red. Such a brightly colored insect is often bad tasting, foul smelling, poisonous or capable of stinging. These bright, contrasting colors are thought to be warning colors and predators soon learn to associate them with unpleasant consequences.

What makes the WXB noxious? It is the plant it feeds on. The ragworts contain poisonous compounds called alkaloids that, when eaten, cause severe vomiting, heart arrhythmias and/or liver damage. The WXB sequesters these alkaloids in their body so that a predator attempting to eat them gets a dose of nasty tasting material. In one experiment lizards were offered WXB that had been fed on Ragwort seeds. After one attempt the lizards refused to eat any other WXB that were presented to them. But lizards willingly ate WXB that had been raised on sunflower seeds, which do not contain alkaloids. The Milkweed bug is protected from predators in the same way – it sequesters the alkaloids found in milkweeds. This condition, in which two or more noxious or poisonous species resemble each other is called Mullerian mimicry. The black and yellow colors of bees and wasps are another example of such mimicry.

But wait, there's more! Not only are WXB nasty tasting they are passionate lovers. Mating pairs often stay in copulo for more than ten hours. I took the mated pair that Sandra found home with me and they were still joined when I went to bed at 11PM. The next morning they had separated by the time I got up. This lengthy coitus doesn't necessarily indicate what you might think. If a female mates with multiple males the last one she mates with fathers most of her children. So many biologists think that such prolonged mating is a type of mate guarding – a way to keep the female WXB from mating with another male before she lays her eggs.

WXB aren't the only insects that can be found on ragworts. In one study five other insect species were commonly found on the same plants with WXB, but four of these were more common on ragworts that had fewer WXB. This suggests that WXB was somehow making the ragwort less inviting for these four species. When WXB were removed by the investigator the abundance of the other four species increased. Further study suggested a reason: mating attempts by male WXB were responsible. Male WXB are eager to mate but rather undiscriminating. They court any insect on their ragwort and it was suggested that this annoyance factor caused the other species to depart from plants that had large numbers of male WXB.

After examining the Butterweed we retraced our steps and some of us adjourned to Donderos' for our customary coffee and conversation.

SUMMARY OF OBSERVED SPECIES: (g=DNFG; b=blooming; f=fruit)
Common Name
Scientific Name
Piedmont azalea
Rhododendron caescens
Pale yellow trillium
Trillium discolor
Common wild ginger
Asarum canadense
Aquilegia canadensis
Solomon’s Seal
Polygonatum biflorum
Sweet Betsy trillium
Trillium cuneatum
Rattlesnake fern
Botrypus virginiana
Sensitive fern
Onoclea sensibilis
Hay scented fern
Dennstaedtia punctilobula
Northern horse balm
Collinsonia canadensis
Jack in the pulpit
Arisaema triphyllum
Black cohosh
Actaea racemosa
Podophyllum peltatum
Perfoliate bellwort
Uvularia perfoliata
Violet wood sorrel
Oxalis violacea
New York fern
Thelypteris noveboracensis

Atamasco lily
Zephyranthes atamasca
Cinnamon fern
Osmunda cinnamomea

Virginia spiderwort
Tradescantia virginiana
Chattahoochee trillium
Trillium decipiens
Chrysogonum virginianum
Shooting stars
Dodecatheon media
Painted buckeye
Aesculus sylvatica
Southern lady fern
Athyrium filix-femina

Solomon’s Plume
Smilacina racemosa
Northern maidenhair fern
Adiantum pedatum

Green violet
Hybanthus concolor
Heartleaf wild ginger
Hexastylis heterophylla
Golden ragwort
Packer aurea
Hydrastis canadensis
Lyre leaf sage
Salvia lyrata
Beaked corn-salad
Valerianella radiata
Field madder
Sherardia arvensis
Hop clover
Trifolium campestre
Purple deadnettle
Lamium purpureum
Carolina geranium
Geranium carolinianum
Packera glabella
White-crossed seed bug
Neacorphyus bicrucis

No comments:

Post a Comment

Post a comment