Ramble Report March 22 2018

Today's Ramble was led by Dale Hoyt.

The photos in this post, except where noted, came from Don's Facebook album (here's the link).

Today's post was written by Dale Hoyt.

20 Ramblers met today.

Announcements:

The Tick Lasso

1) Tick season is here and I recommend the Tick Lasso for easy removal of ticks. I've found it effective. I have not received any remuneration for this recommendation.

2) Tim reported seeing fireflies in his backyard out in Madison County Monday night. [It's very likely that Tim saw the Spring Treetop Flasher.]

3) We welcome new rambler Daniel Borremans to our group.

Today's reading:

1) Linda read a poem by Ranier Maria Rilke:

 

Spring has come back again. The Earth is

like a child that’s got poems by heart;

so many poems, so many verses,

patient toil winning her prizes at last.

Strict, the old teacher. We loved the whiteness

in the old gentleman’s beard, its bright snow.

Now when we ask what the green, what the blue is,

Earth knows the answer, has learned it. She knows.

Earth, you’re on holiday, lucky one: play now!

Play with us children! We’ll try to catch you.

Glad, joyous Earth! The gladdest must win.

Every lesson the old teacher taught her,

all that is printed in roots and laborious

stems: now she sings it! Listen, Earth sings!

Rainer Maria Rilke; translated by Stephen Cohn

Eugenia read a poem by Maxine Kumin: Why There Will Always Be Thistle.

Today's route: From the Visitor's Center to the upper parking lot to the Orange Trail trailhead. Down the Orange trail to the bridge and return to the Visitor's Center through the garden via the Paw paws.

 

Black cherry is now flowering in the upper parking lot

Shortleaf pine cone; note small size

Shortleaf pine cones are retained for several years.

Shortleaf pine bark with resin pits.

Virginia pine male cones

Pine pollen

Everyone who parks their car outside this time of year is familiar with pine pollen, but few know where it comes from (except pine trees). Look carefully at the ends of lower branches on a pine tree and you will see clusters of yellow objects that look like tiny pine cones. If a branch is low enough for you to reach you can tap the end and see a cloud of yellow dust shaken loose. Here are two questions to consider: 1) why is so much pollen produced and 2) why are the pollen-producing cones on the lower limbs and not higher up?

Pines are wind pollinated, so the pollen must be blown through the air to encounter a receptive female cone. As the wind or carries the pollen away from its source it becomes more and more diluted by the turbulence of air – it spreads out and its concentration (no. of grains per cubic foot) becomes lower and lower with increasing distance. Rough calculations suggest that a single pine tree has almost no chance of pollinating a tree located more than 100 – 300 feet away. Producing offspring is the way to win the game of natural selection and trees that didn't make a lot of pollen lost that game.

Why are the pollen cones on lower branches? Many plants avoid self-fertilization and have different strategies to prevent it. (For one example look at the Paw paw account later in this post.) The offspring produced by selfing have a high risk of inheriting two copies of any bad genes carried by their single parent. Such seeds may fail to germinate or will produce weaker plants that don't survive as well as those from outcrossed parents. Placing the pollen cones on the lower branches reduces the chances of self-pollination. Pine pollen is heavy and falls downward, making it less likely to land on the female cones on the same tree.

If pine trees are wind pollinated why do we find distinct species? Why aren't they just one big hybrid swarm? One way of avoiding hybridization between different species is a difference in the time that they release pollen and their female cones are receptive to pollen. For example, Loblolly pine releases pollen from late Feb through the middle of March, whereas Shortleaf pine releases pollen from middle  March to early April. This difference in time serves to minimize the opportunity for hybrid formation.

But how, you ask, could such a difference arise? Here is one possibility. Suppose two things: 1) that the hybrid is not as well adapted to its environment as either parental species and 2) that the pollen release times broadly overlap, with Loblolly releasing in late February through March and Shortleaf releasing in March through early April. Then in March there will be a greater opportunity to form hybrids. The hybrids produced will be less fit than the non-hybrids (the second assumption). This means that trees releasing pollen in March are less successful in producing offspring than those releasing pollen in February or April. Over many generations the number of trees with intermediate release dates will dwindle away. Natural selection will have caused the two species to release pollen at different times.

Single flower Carolina Jessamine

Carolina Jessmine high in tree

Crossvine climbing a pine

Crossvine flower
Crossvine flowers later in spring

Vines

The early flowering spring ephemerals like Hepatica and Bloodroot capture most of our attention this time of year. Many of these are perennial but their above ground parts wither after seed is produced. Others, like Hepatica, retain their leaves throughout the year. The early flowering vines, Carolina Jessamine and Crossvine, share this evergreen perennial habit with Hepatica. But instead of creeping about the forest floor they clamber high into the trees where they can bloom in the sunlight. The Carolina Jessamine is probably more familiar to most because it is often planted in a sunny spot by a fence. But the Crossvine produces equally attractive showy masses of large, tubular flowers, red-orange on the outside and yellow on the inside. It blooms at about the time hummingbirds return to our area and is an important source of nectar.

Marcesence

Some trees retain their dead leaves throughout the winter. No one knows why. It may be inconsequential. In autumn deciduous trees withdraw the nutrients contained in the leaves and then form a layer of cells that are only weakly connected to the leaf petiole. This layer of tissue, called an "abscission layer," also seals off the dying leaf from the twig. Once the leaf is dead it may not matter if it drops off right away. An argument can be made that in areas with heavy winter snowfall retained leaves would make a tree more susceptible to broken limbs. But the snow load will quickly remove any

Most people associate marsecence with Oaks, but other trees retain their leaves as well: Beech, Hophornbeam and Chalk Maple.

A Script Lichen on the bark of American Beech
Can you decipher the hidden message?

Script Lichen

Just to review: a lichen is a composite organism; an association of a fungus and a "photobiont." The photobiont is a unicellular organism that maybe a green alga or a blue-green bacterium (a cyanobacterium). The photobiont carries out photosynthesis, making sugar from water and carbon dioxide, using sunlight as an energy source. The sugar is shared with the fungal host, although a case could be made that it is stolen by the fungus.

This lichen is named for the dark, curly cued lines that look like some sort of coded writing. But the script is not a hidden message; it is the fungal spores that are produced by the dark code words of the fungus.

Little Nest polypore fungus on twig

Speaking of lichens, Don found a twig with a group of Little Nest polypore fungi growing out of it.

Packard's Lichen moth caterpillar

'

Frolicking among the fungi was a tiny caterpillar that had us stumped. It had a peculiar way of moving that suggested it might not be a Lepidopteran (butterfly or moth caterpillar). The only group I could think of with a similar larval form was a type of hymenopteran called a sawfly. (Hymenopterans are ants, bees, wasps and related forms). Sawfly larvae have more than five pairs of fleshy legs on their abdomen; moth caterpillars have five or fewer. We tried counting the legs, but the little bugger kept moving and we couldn't get an accurate count. But Don and Katherine pursued identification after the ramble and came up with a convincing ID: Packard's Lichen moth.

Lichen moths are a small group of moths related to the common Wooly Bear. Unlike their relatives they don't feed on the leaves of herbs or trees; they feed on cyanobacteria (formerly known as blue-green algae) and lichens that grow on tree trunks and other objects. What a peculiar lifestyle!

This was one to add to my life list, thanks to Don and Katherine's diligence. I'm lichen them more and more.

Bench back with Carpenter bee nest tunnels exposed by Pileated woodpecker

Bench with Pileated woodpecker damage

There is an old bench located at the bend in the Orange trail next to the large erosional gully. Many of the boards that make up the seat and back are cratered with excavations made by Pileated woodpeckers seeking food: the larvae of carpenter bees.

As many home owners know, carpenter bees chew long tunnels in exposed wood. These tunnels are used to house the larvae of the bee. The female bee collects pollen and nectar from flowers and brings them to the end of her tunnel nest. There she molds the pollen-nectar mass into a ball and lays an egg on it. She then seals off the egg with a partition made of chewed wood and saliva. She continues foraging, gradually filling the tunnel from the end with a sequence of partitions, each with a single developing bee larva.

How the woodpeckers learned about this is unknown, but learn they did. Pileated Woodpeckers are especially fond of carpenter bee larvae than they have the power and strength to quickly break through the tunnel sides and extract the bee babies. You can see a Pileated Woodpecker attacking a carpenter bee tunnel constructed in a two by four here. (Apologies for the sound track -- I had the radio on before I noticed the woodpecker and it (the radio) was too far away to turn off. Emily came to the rescue.)

Orange Trail Plants

Lion's Paw

Christmas fern fiddleheads

Painted Buckeye newly emerged leaves
New leaves of many plants are often red.
The color is produced by anthocyanin, a red pigment that acts as a sunscreen.

Perfoliate Bellwort
The leaves appear to have been pierced by the stem, hence the name
perfoliate means "through the leaf"

;

Rattlesnake fern
The fertile frond that produces spores is starting to develop at the front of the leaves.

Rue Anemone continues to bloom, sometimes in large groups.

The first flower of Wild Geranium we've seen.

Tripartite violet; named for the three branched leaves
We first discovered it in the Garden several years ago; it continues to do well and spread.

Snakeskin liverwort among the moss by the side of the creek.

A clump of Mayapple

A Mayapple flower bud forming between two leaves.

Scattered alongside the Orange Trail and the adjacent slopes are many colonies of Mayapple. The plants in each patch are all clones of one another, each stem produced from a common underground rhizome. Most of the stems bear a single, large leaf but a few in each colony support two leaves. At the point in the stem where the two leaves are attached is a flower bud, very small this early in the season. In a few weeks it will produce a white flower 1-2 inches in diameter and, after that, an edible fruit. But that fruit is the only edible portion of the plant. Every other part of the plant is loaded with a poisonous chemical, podophylline, its name derived from the genus name (Podophyllum) of the plant. The toxic effect of podopylline is at the cellular level. It inhibits the formation of molecular structures called microtubules inside cells. Microtubules are like stiff chains, they can be used to both pull and push things around. Like chains, they are made of smaller subunits and their length is determined by how many subunits join together. Podophylline inhibits the assembly of these subunits into microtubules. One of the effects of podophylline poisoning is that cells can no longer divide. In cell division the chromosomes duplicate and are then separated, one copy of each chromosome going to each daughter cell. It is microtubules that pull those chromosomes into each daughter cell. So the poisoned cell cannot divide and it dies. This is the principal underlying cancer chemotherapy. Cancerous cells divide rapidly and chemotherapeutic compounds poison dividing cells. But there are other, healthy cells in the body that also divide. The trick in chemotherapy is to kill the cancerous cells before the damage to the healthy cells is too severe. Podophylline was once considered for chemotherapy, but it caused too many severe side effects and could not be tolerated.

  

Paw paw flower
The green stigma is in the center, surrounded by numerous yellow anthers that are shedding pollen.

A visit to the Paw paw patch revealed that more flowers had opened since last week's ramble and many had well-developed anthers spilling pollen. Last week none of the flowers we examined showed any signs of shedding pollen, but had prominent stigmas (the part of the flower that receives pollen). Today we saw that the stigmas looked withered in the flowers that had open anthers. This suggests that Paw paws use differences in the timing of stigma receptivity and pollen shedding to prevent a flower from fertilizing itself. This is a wide spread strategy in flowering plants, common enough to have fancy botanical names for the process: protogyny and protandry. (The prot- prefix means first, the –gyny suffix means female and the –andry suffix means male.) So in a protogynous flower the stigma is receptive before pollen is released and in a protandrous flower pollen is released before the stigma is receptive.

A few lucky ramblers got to see a spectacular Phantom Crane Fly that landed on Rick's jacket as we walked up the hill. If you've never heard of or seen one of these beautiful insects you should visit this link to see what you've missed. It floated off before we had a chance to summon Don for a photograph.

SUMMARY OF OBSERVED SPECIES:

Virginia Pine	Pinus virginiana
Loblolly Pine	Pinus taeda
Shortleaf Pine	Pinus echinata
Black Cherry	Prunus serotina
American Beech	Fagus grandifolia
Script Lichen	Graphis sp.
Sourwood	Oxydendrum arboreum
Crossvine	Bignonia capreolata
Lichen moth caterpillar	Cisthene packardii (?)
Little Nest Polypore fungi	Poronidulus conchifer
Yellow Jessamine	Gelsemium sempervirens
Common Blue Violet	Viola sororia
Christmas fern	Polystichum acrostichoides
Rattlesnake Fern	Botrypus virginianus
Lion's Paw	Prenanthes serpentaria
Mayapple	Podophyllum peltatum
Perfoliate Bellwort	Uvularia perfoliata
Painted Buckeye	Aesculus sylvatica
Rue Anemone	Thalictrum thalictroides
Wild Geranium	Geranium maculatum
Amur Honeysuckle	Lonicera maackii
Common Elderberry	Sambucus canadensis
Wood Rush	Luzula acuminata
Violet Wood Sorrel	Oxalis violacea
Red Maple	Acer rubrum
Snakeskin Liverwort	Conocephalus conicum
Kidneyleaf Buttercup	Ranunculus abortivus
Three-parted Yellow Violet	Viola tripartita
Cranefly Orchid	Tipularia discolor
Phantom Crane Fly	Bittacomorpha clavipes
Paw paw	Asimina triloba