Of Skunks and Cabbages

We live just a few miles from the southern-most population of skunk cabbage, Symplocarpus foetidus.  These fascinating plants look like cabbage (kind of) and its leaves and flowers give off a strong odor (the skunky part of the name).  The specific name foetidus comes from Latin and means smelly.  Skunk cabbages live along creeks and in swamps across eastern Canada, the northern US east of the Great Plains and as far south as Tennessee and North Carolina.  On an early spring morning, I hiked up an unnamed branch of Swearing Creek.  As I rounded a bend, dozens of bright green plants were emerging from the creek and its soggy banks.  The flowers were finished but some decaying fruits remains. 

A population of skunk cabbage, Symplocarpus foetidus, in Piedmont North Carolina

Skunk cabbage is one of the earliest flowering plants in its range with the flowers produced in deep winter.   Snow covers the ground in many places when skunk cabbage flowers.  Its most amazing trick is the flowers can melt their way through snow.  Skunk cabbage uses a special thermogenic type of respiration to raise the flower temperature above that of its surroundings, melting snow and giving off its foul odor.  This smell attracts early emerging flies to act as pollinators.  

Skunk cabbage with decaying spathe and spadix

Skunk cabbage emerging from the water

Spathiphyllum with a flower bearing spadix
and the white, leaf-like spathe

Skunk cabbage is in the family Araceae that also includes Spathiphyllum, a familiar houseplant.   The Araceae produce distinct flowering structures; the spadix and the spathe.  The spadix is an inflorescence, a group of flowers that develop into fruits.  The spadix is surrounded by the leaf-like spathe.  The spathe of skunk cabbage is green with purple stripes. The purple color and strong smell resembles rotting flesh and attracts the fly pollinators.  The largest flower in the world, the titan arum, Amorphophallus titanium, is in the same family with a 10-foot flower, purple spathe, a giant spadix and fetid smell. 

I hope to visit the skunk cabbage site again next winter and find flowers melting their way through snow, in full stench.

Winter Decomposers II: The Return of the Fungi

Fruiting bodies of Giraffe spots 
Peniophora albobadia

I am on a mycological kick so I will keep kicking.  Diane and I found a couple more interesting fungi growing on dead sticks recently. 

The first is giraffe spots Peniophora albobadia.  What you see with giraffe spots is really the fruiting body, the spore producing structure, growing tightly appressed to the stick.  Most of the fungus is the hyphae that are rotting the dead wood from the inside.  The fruiting body of this crust fungus is flat and brown with white margins.  This fungus often grows in groups and as the name suggests look like the pattern of spots on giraffes.  Giraffe spots is an important decomposer but is also a pathogen on peaches, nectarines and apricots. 

Giraffe coat pattern

Petr Kratochvil 

(publicdomainpictures.net)

Giraffe spots Peniophora albobadia
detail showing pattern

The second nice fungus was growing on a dead limb of the ornamental plant photinia.  This shelf fungus is a polypore with light and dark rings on the top of the fruiting body.  On the underside of the cap there are many pores (naturally) arranged in a labyrinthine pattern.  The scientific name of this fungus Daedalea quercina is quite apt.  The specific name, quercina, refers to the genus of oak, Quercus.  

Daedalea quercina showing the top of
the fruiting body with alternating light and dark rings

Daedalea quercina showing the underside of the
fruiting body with its labyrinthine pores

Our specimen was not growing on oak but this fungus is common on dead branches of that tree. The genus name Daedalea goes back to Greek mythology, named for Daedalus who built the Labyrinth for King Minos of Crete.  In the Labyrinth was imprisoned the Minotaur, a monster who ate sacrificial Athenian children.  The pores on this fungus, with their twisting chambers and passages could be a maze from which escape is futile. 

Ents, Christmas decorations and a nest: A lichen story

Lichens are fascinating.  Slow growing, pulling nutrients from the air and converting rocks into soil these consummate symbionts are found on all continents, grow from sea level to mountaintops and from the tropics to the arctic.  Their colors range from red and orange to gray-green to bright yellow.  Lichens are a combination of a fungus, and a photosynthetic microbe, either a green alga or a  cyanobacterium (formerly know as blue-green algae). 

Lichens on a sea cliff in Wales

Lichens are classified according to the fungus they contain rather than the by their photosynthetic partner.  The body of the lichen, the thallus, is made of fungal filaments called hyphae.  Within the thallus is the photosynthetic alga or cyanobacterium.  The photosynthetic cell produces sugars for the fungus and the fungus provides water and nutrients to the alga.   A lichen’s growth form is different from either the fungus or the alga when they live independent of each other. 

Lichens can live in very harsh environments and are among the first colonizers of bare rock.  Lichens secrete acids that begin the chemical weathering of rock to produce soil.  Lichens also commonly grow on trees trunks and branches taking water from rain and dew and inorganic nutrients from dust and bird droppings.  Lichens are very slow growing, a few millimeters per year in some cases, because optimal growth conditions may only occur a few hours a day.  In the high arctic lichens grow on the ground and are grazed by large mammals.  This is why one of the arctic lichens has the common name reindeer moss. 

Despite living in forbidding environments lichens are very susceptible to air pollution, particularly sulfur dioxide.   In urban Washington, DC parks, the lichen diversity is much lower than in parks in the surrounding area.  This difference in lichen distribution is due to the air pollution in town.

Lichens exhibit a number of different growth forms.  Some grow as a thin layer tightly appressed to rock, cemetery headstone or tree trunk.  These are the crustose lichens since they form a crust on their substrate. 

 

A crustose lichens in south Florida

Foliose lichens have flat, leaf-like thalli whose edges are not attached to the surface on which they grow. 

 

Parmotrema sp. a foliose lichen in North Carolina

Fruticose lichens are three-dimensional and branched.  Fruticose lichens resemble little trees or bushes and are used by model railroaders to add tiny trees to their displays.  Treebeard, the Ent in J.R.R. Tolkein’s The Lord of the Rings, had a beard of fruticose lichens

Cryptothecia rubrocincta or Christmas lichen is one of the most beautiful of all the lichens.  It grows throughout tropical America and extends its range into the subtropical regions of the United States.  You can find it growing near the coast from Texas to Florida and into North Carolina.  The Christmas lichen’s range tracks very closely the distribution of the cabbage palmetto.  This crustose lichen stands out on the tree trunks that support it because it is bright red.  The color of this lichen varies from red and pink to white and looks much like a Christmas decoration on the tree.  Two chemicals, beta-carotene and chiodectonic acid cause this lichen’s red color.  The algal symbiont produces the pigment beta-carotene and chiodectonic acid is produced by the fungus.  Both these compounds probably protect the lichen from ultraviolet damage and other environmental stresses. 

 

Cryptothecia rubrocinata, Christmas lichen in a Florida cypress swamp

Members of the foliose lichen genus Usnea is widespread and grows on tree trunks and small branches.  Usnea is gray-green in color and resembles small plants of Spanish moss.  Usnea strigosa has reproductive structures found on fungi that are not lichenized.  These flattened cups (apothecia) produce spores and are typical of cup fungi.  The apothecia release spores that germinate and the fungal hyphae must find their particular species of alga to reestablish the lichen symbiosis.

Usnea strigosa, a fruticose lichen with apothecia in North Carolina

 The scientific name of Spanish moss is Tillandsia usneoides, so-named for its resemblance to the lichen.  The Northern Parula is a warbler that winters in Central America and on Caribbean islands. In spring, Parulas fly to eastern North America where they nest.  On the coastal plain of the southeastern United States, the Northern Parulas make their nests of Spanish moss while further north they use Usnea for nest material.  Even this warbler notes the resemblance between the Usnea and Spanish moss.    

Winter Decomposers

Fungi make their living a variety of ways.  Some are parasites taking nutrients from living organisms.  Some are symbionts associated with the roots of plants that transfer inorganic nutrients to the plant in exchange for sugar and other organic molecules.  And some fungi decompose formerly living material.  These decomposers mainly break down dead plant parts. Without the decomposers, a walk in the woods would be wading through a sea of dropped leaves, a tangle of downed branches and impassable barriers of dead tree trunks.   We usually don’t see these vital components of the ecosystem except when they make their reproductive structures called fruiting bodies or more familiarly, mushrooms.  Most of the fungal biomass is in microscopic threads of cells called hyphae.  The hyphae of the decomposers growth throughout the dead plant parts and release enzymes that break down highly resistant plant polymers like cellulose and lignin.  The fungus then absorbs the breakdown products of these polymers and the plant parts are recycled.  Winter is not typically a good time for finding mushrooms in this area but the decomposers are an exception. 

Turkey tail fungus, Trametes versicolor, on a rotting log

On some recent hikes, we found several of these winter decomposers. One prominent fungus on dead tree trunks is the turkey tail (Trametes versicolor).  The flat caps of the turkey tail grow in large groups on dead trees.  They are quite striking with alternating bands of varying shades of brown, gray and white that resembles the tail of a turkey.  On the underside of the cap are small oval pores that produce the spores of the fungus. These pore-bearing fungi are Polypores, classified in the family Polyporaceae. The spores float through the air and if lucky enough to land on a dead tree, can establish another colony of turkey tail fungus. 

Fruiting bodies of Poronidulus conchifer

Small white mushrooms growing on small dead branches is Poronidulus conchifer another Polypore. The pores are found on the lower side of the fruiting body.  This fungus is closely related to the turkey tail.  The scientific name quite descriptive. The genus, Poronidulus, is from the Latin meaning “little nest with pores”.  When the fruiting body is small it is curled up and look like little bird's nests.  Since it is a The species name, conchifer, is Latin for “conch bearing” because the larger fruiting bodies look very shell-like. 

A common large mushrooms growing on downed logs and on dying live trees is the oyster mushroom Pleurotus ostreatus. This fungus is has a worldwide distribution and is a major decomposer of wood.  It is also a choice, edible mushroom.  The whitish caps of the fruiting body resemble oysters and that gives it both its common name and the species name (ostreatus is from Latin for oyster).  The fruiting body usually grows in groups on a tree trunk or log.  The underside of the mushroom bears spore-producing gills typical of members of the order Agaricales, the gilled mushrooms.  Oyster mushrooms make their living decomposing wood but have a more ominous source of nutrients.  Pleurotus ostreatus is also a carnivore.  Hyphae of the oyster mushroom produce droplets of a toxic protein that paralyzes nematodes found in and on the rotting wood.  Oyster mushroom hyphae then invade the body of the paralyzed nematode and consume the unfortunate worm from the inside. 

 

Oyster mushroom (Pleurotus ostreatus) showing spore-producing gills

Oyster mushroom on log with their typical oyster shape

Even in winter, the process of decomposition goes on, carried out by a group of fascinating fungi. 

The Hunt for the Great White Squirrel

Gray squirrels are, well, gray.  But not completely gray.  Many have brown mixed in with the gray and most have a white belly.  In our corner of North Carolina, we have the eastern gray squirrel (Sciurus carolinensis).  Its scientific name means squirrel of the Carolinas, but the eastern gray squirrel ranges from south Florida to southern Canada and west to where the forests give way to the prairies. 

Gray squirrel with normal coloration.

Recently a friend told me of a white squirrel in her suburban neighborhood.  Diane and I decided we would have to hunt for the great white squirrel.  Unlike Ahab who had to search three oceans to find his prize, we drove through a leafy suburb.  There were lots of squirrels, on the lawns and in the trees but they were all gray.  Then, rounding a corner, we saw it.  The white squirrel bounded across the road, into a yard and ran up a tree.  We quickly noticed the squirrel was not pure white but had a gray patch on its head and a gray stripe down its back.  As we looked more closely, we could see this squirrel’s eyes and nose were dark.  This squirrel was a white eastern gray squirrel but it was not an albino.  Albinos cannot make the pigment melanin so they have white fur, pink eyes and pink noses.  This squirrel was leucistic, able to make melanin in parts of its coat, eyes and nose but could not make melanin in the rest of the its body.   A number of genes are responsible for leucism and our white squirrel undoubtedly had a mutation in one of these genes. 

Leucistic gray squirrel with gray
stripe down the back.

Leucistic gray squirrel showing
 white fur, gray on top of
head  and dark eyes.

White squirrels are rare because the mutations happen infrequently and because the white squirrels that are born are easy for predators to see and catch.  We have been watching this white squirrel for a month and it has not been caught by a hawk or coyote.  If this squirrel reproduces, there is a chance some of its offspring will be leucistic too.  The white squirrel may be able to survive in this neighborhood with the help of people.  They could provide food in bird feeders and limit threats from predators.  

The mountain town of Brevard, NC has a famous population of white squirrels established in the 1950s.  Brevard passed an ordinance to protect the squirrels and has an annual White Squirrel Festival complete with fun run, bands, food trucks and a white squirrel photo contest.

White forms of animals have cultural and spiritual significance around the world.  The white buffalo is revered by the native people of the American plains.  According to the Kitasoo Nation, Raven made the Spirit Bear, a white variant of the American black bear found on the coastal islands of British Columbia, to remind the people of the age of ice that came before.  The Tsonga of South Africa consider the white lion as most sacred.  For Captain Ahab, Moby Dick was a manifestation of evil.  Beyond genetics and natural selection, I wonder about the meaning of this white squirrel. 

Nitrogen is Expensive, Carbon is Cheap

Bradford pear (Pyrus calleryana) showing red color
from anthocyanin,and yellow from xanthophyll.

Every fall, trees put on a spectacular show.  As the days get shorter and the nights cooler, trees undergo a transformation.  From the maple forests of New England to the aspen groves of the American west  trees show a fantastic range of colors; red, orange, yellow, purple.

This extravagance is the basis of an important tourist industry, catering to “leaf peepers”.  Vermont’s hotels and restaurants bring in more than $100 million dollars in October much of that from people coming to see the colors. 

From spring to later summer, most trees are green.  The shade of green in trees shows a wide variation between species but all those shades are due to the photosynthetic pigment chlorophyll.  This biochemical workhorse, found in the chloroplasts of leaves, participates in food production and oxygen generation from spring to fall.  Chlorophyll is not the only photosynthetic pigment in leaves.  Carotene and xanthophyll are present in the chloroplasts too and work in concert with chlorophyll to carry out photosynthesis.  Carotene is orange (it gives carrots their color) and xanthophyll is yellow.  Plants have another type of pigment called anthocyanin that comes in many colors including red and purple.  Anthocyanin is not involved in photosynthesis but protects plants from environmental stress.  In summer carotene, xanthophyll and anthocyanin are invisible because there is so much chlorophyll in the leaves. 

Leaves of sugar maple (Acer saccharum) with a
range of fall colors 

The reason we have fall color is chlorophyll contains nitrogen.  Nitrogen is usually in short supply for plants.  They have to take up this scarce resource from the soil, sometimes with the aid of symbiotic fungi associated with plant roots.  Plants then transport the nitrogen up to the leaves where it is used to make chlorophyll. 

Deep red anthocyanin in the leaves of
Euonymus americana

                                                                                      Carotene, xanthophyll and anthocyanin are made only of carbon, hydrogen and oxygen.  These elements are available in abundance for the plants coming from CO₂ in the air and H₂O taken up by the roots.  For plants, nitrogen is expensive and carbon is cheap.  In the fall, trees do not want to waste the expensive nitrogen in chlorophyll by dropping it with the leaves, so the chlorophyll is broken down and the nitrogen stored in twigs for use in next year’s chloroplasts.  As chlorophyll disappears from leaves carotene, xanthophyll and anthocyanin can shine through.  These pigments are not recycled because they are made of cheap resources and the trees drop them to the ground with the leaves. 

As we move from the bright green of summer to the brown of winter let’s thank cheap carbon and expensive nitrogen for the dazzling fall show.

The Disappearance

When birds are migrating in spring it is fairly easy to notice when a new species arrives.  One day yellow-billed cuckoos are not here and the next day they are.  But in fall migration it is harder to track the disappearance of a species when they fly south.  Since absence of evidence is not evidence of absence, we paid particular attention to the last date we recorded Chimney Swifts and Ruby-throated Hummingbirds in our area.  These small birds undertake heroic migrations in the fall of the year.  Some Ruby-throated Hummingbirds fly non-stop across the Gulf of Mexico and Caribbean Sea to their wintering territories in Mexico and Central America.  Others take the land route around the Gulf through Texas and further south.  Chimney Swifts winter in the Amazon Basin of South America with a hazardous migration similar to that of the hummingbirds. 

We had a hummingbird family in our yard this summer.  A male and a female visited our feeders daily and later in the summer at least one immature hummingbird was with them.  Then in August, the male disappeared.  Did he and the family go south?  Absence of evidence.  In August and into September large numbers of female and immature hummers were in our yard drinking the sugar water.  The number of hummingbirds started to decline in October and we made the final sighting of the year on October 19. 

Chimney Swifts entering a chimney at sunset

Chimney swifts disappeared a few days before the hummingbirds, on October 15.  In the fall of the year, you can find large flocks of migrating chimney swifts around their roosting spots.  Since these birds cannot perch on a limbs or wires, they must cling to a vertical surface, like a chimney, to nest or sleep. Before Europeans entered the new world, Chimney Swifts probably roosted in hollow trees and on cliffs.  

 A local high school has a stack for an unused furnace that is ideal for a chimney swift roost.  We have recorded over 3000 swifts flying into this stack during September.  The swifts begin flying near the chimney around sunset giving their chattering call.  Then the number grows and they begin to form a vortex of swifts hundreds of yard wide.  A half an hour after sunset as the light is disappearing the swifts begin to enter the stack.  The vortex gets smaller and smaller until the last swifts fly into the chimney as total darkness descends.   

We look forward to these birds showing up again next spring.