Lichens - Neighborhood Naturalist

Nature you can find in town and the nearby countryside
Corvallis, Oregon
Winter 2010-11
Lichens
article and photography by Lisa Millbank
L
ook out the window, and chances are, you’ll see
a remarkable form of life—a lichen. While it
looks like a single organism, a lichen is actually
an intimate partnership that weaves together two or
three distant branches of the tree of life: an alga and/or a
cyanobacterium, and a fungus.
Lichens are overlooked, probably because they tend
to be small and hard to identify. There aren’t many field
guides for non-scientists, partly because lichenologists must
sometimes use chemical tests and microscopic features
to tease apart similar-looking species. Lichens may look
different when wet or dry, and different growing conditions
can affect their appearance. Species belonging to different
genera or families may look frustratingly alike. But while
there are multitudes of grayish crust-like lichens that
may vex an amateur lichen-lover, there are also plenty of
beautiful and distinctive ones that anyone can learn.
Cross-section of a foliose lichen
upper cortex
illustration by Don Boucher
photobiont layer
medulla
lower cortex
The tough fungal tissue of the cortex protects the algae or
cyanobacteria in the photobiont layer (algae in this example),
and the spongy, fibrous fungal tissue of the medulla.
An Oregon Ash twig is home to many lichens: Hypogymnia
physodes (puffy and greenish, in center), a Ramalina and Evernia
prunastri (flat grayish straps), Parmelia sulcata (flat greenish ones
by Hypogymnia), among others. Lichens are at their best in winter!
A lichen’s basic structure is provided by the fungal
partner, the mycobiont. The photobiont, which may be an
alga, cyanobacterium or both, grows in a layer beneath a
protective structure of fungal cells. Lichens take in carbon
dioxide, water, and tiny amounts of mineral nutrients and
reduced nitrogen that they get from the environment.
Even rainwater running down a branch and dripping
on a lichen can be one way the lichen gets the nutrients
it needs. Inside the lichen, the photosynthetic partner
uses sunlight to make carbohydrates, just like a garden
plant. The photobiont shares the food it produces with
the mycobiont. Lichens with a cyanobacterial partner can
reduce their own nitrogen from elemental nitrogen in the
atmosphere, much like nitrogen-fixing bacteria do in the
root nodules of a bean plant.
Most lichenologists consider a lichen to be a symbiotic
relationship of mutual benefit to both partners, but a few
have suggested that the fungus may actually be practicing
parasitism of the photobiont. If so, the fungus is a gentle
parasite, since its life depends on the survival of its captive
photobiont. Whether mutualism or parasitism, the
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 1
Foliose lichen
Fruticose lichen
Crustose lichen
Pseudocyphellaria anomala, or Netted
Specklebelly Lichen. A foliose lichen is leaflike. The dots are for asexual reproduction.
An Usnea, or a “beard lichen.” A fruticose
lichen has a shrubby structure. In Usnea,
the “hairs” grow off central “cords.”
This is a Lecanora, or a “rim-lichen.” This
lichen forms a crust on the branch, and
the little discs, or ascocarps, make spores.
relationship is an ancient and successful one. The oldest
unequivocal fossil of a lichen is about 400 million years
old. The fossil record is poor, so the evolution of lichens is
difficult to understand. Partnerships between fungi and a
photobiont have almost certainly evolved independently
many times, from diverse lines of fungi.
cyanobacterium is usually one of a few genera that are
commonly found in lichens.
Lichens are exceedingly tough little things. They get by
with fewer nutrients than almost any other organism, which
lets them grow on bare rock, bark, concrete and other surfaces
that are inhospitable to almost everything else. Although
The alga and/or cyanobacterium found in a given lichen most lichens prefer cool, damp growing conditions, they
isn’t always specific to that particular lichen. That’s why can withstand drought, extreme cold and the fierce summer
lichenologists classify lichens as fungi, because, in general, sun by shriveling up
each species of fungus found in lichens is the dominant and entering a state
partner, and seems to control the form and biochemical of cryptobiosis, where
activity of only one species of lichen. The mycobionts in metabolic activity
the vast majority of lichens are in the sac fungi phylum, stops temporarily.
Ascomycota. Yeasts, morel mushrooms, Penicillium Lichens have even
molds and cup fungi are also ascomycetes. The alga or traveled into space
as experimental
subjects. After
e x p o s u re t o t h e
Ne i g h b o r h o o d Na t u r a l i s t
damaging radiation,
promotes interest about nature
vacuum and cold of
in mid-Willamette Valley
space, they revived Oakmoss (Evernia prunastri) is used to
backyards, neighborhoods, and
quickly and looked make perfume. It’s a common lichen whose
countryside.
color is lighter on the lower surface.
perfectly healthy!
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©2010 Don Boucher and Lisa Millbank.
But the price they pay for their extreme lifestyle is very
slow growth. Plants easily outcompete lichens, so lichens
get by in places where plants can’t grow well. Oakmoss
(Evernia prunastri) grows a few millimeters per year. With
a growth rate of about 30mm per year, Fishnet (Ramalina
menziesii) is a fast-growing lichen. Certain lichens can live
for centuries, even millennia, making them some of the
world’s oldest living things. Some lichens that form rosettes
on rocks have relatively constant growth rates, often less
than 0.5mm per year. When geologists want to know how
long rocks have been exposed to light (such as after a glacier
has retreated), they use the science of lichenometry to make
an estimate, based on the size of the lichens they find.
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 2
Although lichens have no roots, some kinds cling to a
surface with tiny root-like rhizines. Others are so tightly
integrated with their substrate that they can’t be peeled off.
Some hang freely from a little stalk. Unlike plants, they
get little nutrition from the substrate on which they grow,
with the possible exception of some minerals. Though
they often completely engulf a tree’s branches, they aren’t
harmful. The chemical composition and physical structure
of the bark may determine which species of lichens can
grow on a particular tree. When lichens grow on rock, they
sometimes secrete chemicals that gradually attack the rock
itself. In this way, they contribute to the natural process of
weathering, and enrich the soil with minerals.
An Anna’s Hummingbird incubates eggs in the beautiful nest she
In the Willamette Valley,
most lichens grow on trees.
Look at the rough bark of
a deciduous tree, and most
surfaces are covered with
lichens. Now look even closer,
using a hand lens. The spaces
between the larger foliose and
fruticose lichens are filled with
tiny, multicolored crustose
lichens. The real estate on that
tree trunk is filled to capacity,
This tiny Golden-crowned and the tenants are jostling for
Kinglet fills her belly with space. Over the lifetime of the
insects and spiders in lichens. tree, bits of soil accumulate in
the cracked bark, and plants
begin to grow on the soil. These can crowd out lichens, and
eventually claim a portion of the tree for themselves. On
an old Bigleaf Maple, mosses, liverworts and Licorice Ferns
dominate anywhere that organic matter has accumulated.
Lichens dangle from twigs or grow on the slender branches
and smooth patches of bark, where the plants can’t get a
foothold. A branch is a slow-motion battleground for light,
nutrients and space. A rock or a weathered old board may
be equally contested space, perhaps with a different set of
lichens and plants.
Lichens may not look
appetizing, but they’re
on the menu for some
animals. When windstorms
tear lichens down from
the treetops, they can be a
welcome food supply for
deer and elk. At higher
elevations, where snow
cover makes finding food
Xanthoparmelia cumberlandia difficult, lichen blown onto
dramatically decorates rocks the snow surface is an easy
meal for a hungry deer. It’s
along the Corvallis riverfront.
made from spiderweb, Usnea and Ramalina lichens, with Parmelia
sulcata stuck to the outside. She successfully raised two babies.
probably not the tastiest meal, and many kinds of tree
lichens are too low in protein to be a deer’s staple food,
but they’ll help a deer get through hard times.
Lichens (along with mosses and liverworts) vastly
increase the habitat available for tiny insects and spiders
on tree trunks and branches. Some moth caterpillars, slugs
and mites feed on lichens, and many insects can lay eggs
or pupate within them. Birds, such as Brown Creepers,
kinglets, nuthatches, chickadees and warblers, find a lot
of their food by methodically picking through this rich
source of invertebrates.
Animals who make their homes in the treetops have
easy access to lichens, and
some local lichen-lovers
include the Northern Flying
Squirrel and several types
of tree vole. Lichens are
important winter food for
Northern Flying Squirrels,
but many other kinds of
animals use lichens mainly
for insulation or structural
Two lichens that are related may look surprisingly different. On the
left, a shrubby little Ramalina dilacerata is covered with sporebearing discs. Fishnet (Ramalina menziesii), on the right, is the
enormous, net-like hanging lichen that drapes over branches. Fishnet
is probably the easiest lichen to identify!
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 3
materials in their burrows and nests. Hummingbirds use
lichens and spiderwebs. The elastic strands of fruticose
lichens like Usnea are favorites of Bushtits, who use them
for weaving a hanging, sock-like nest.
Because they collect nutrients from the air and the
rain, many lichens are vulnerable to air pollution. Surveys
of lichens with varying sensitivities to pollutants can be
used to map air quality. Besides air pollution, habitat loss
is another threat to lichens. Old-growth forests are home
to certain lichen species that take generations to regrow
in the tree plantations that replace clearcuts. Some of the
cyanobacterial lichens that are lost, such as Lobaria oregana, Xanthoria polycarpa, or Pincushion Sunburst Lichen, is a small,
are important contributors of nitrogen to the forest soil. cheerful lichen with many cup-like ascocarps.
Reproduction in lichens can be a little complicated
because of the dual nature of the lichen structure. Somehow,
both the fungus and a photobiont have to end up together.
There are several straightforward asexual solutions to this
problem. Many lichens make soredia in structures called
soralia. A soredium is a clump of photobiont cells wrapped
in fungal filaments. The tiny particle blows away from the
parent lichen, and if it’s lucky, lands in a suitable habitat.
Another way is to form little outgrowths on the surface of
the lichen body, called isidia. These bits will break away
and begin growing elsewhere. Large pieces that break away
from certain kinds of lichens may establish themselves
where they land. The effects of wind, rain, and even animal
activity can help lichens spread and colonize new locations.
from another lichen. It’s intriguing that the droppings of
lichen-munching mites sometimes contain fungal spores
and algal cells that may help lichens reestablish themselves
where they’re deposited.
Just how lichens exchange genes with other individuals
to reproduce sexually is poorly understood. What is known
is that the sexual process is restricted to the fungal partner
in the lichen. Lichenologists think that a spore may land
on a thread-like trichogyne that protrudes from the surface
of another lichen. Although it’s not a perfect analogy, it
helps to think of the spore and trichogyne as something
like a pollen grain and the stigma of a flower, on which
the pollen lands. Soon, an ascocarp (which often looks
like a little cup) forms at the spot, containing special cells
Many lichens also produce asexual spores from pycnidia, with genetic material from the both parents. The resulting
little pockets in the lichen. When a spore is carried away spores made in the ascocarp enhance the genetic diversity
from the spore-bearing structure of the parent lichen, it may of the lichen. This account of the sex life of lichens is a
land in a suitable place for germination. The tiny fungus little speculative, as the process hasn’t been fully observed.
faces a huge problem: it needs to find a photobiont. Perhaps Lichens still keep some secrets!
some spores may happen to land next to a compatible
photobiont, or perhaps it can even steal a photobiont
Lichens, like other fungi, are rich sources of unique
chemicals. Lichens may have novel antibiotic compounds
that could be used in medicine. Traditional medical systems
from around the world have used lichens like Usnea for
bacterial infections. Like other fungi, lichens need to
protect their tissues from bacterial growth, and they do so
with a broad range of powerful antimicrobial chemicals.
The deciduous forests of the Willamette Valley are some
of the best places to enjoy lichens. When the leaves have
fallen and cool, wet weather prevails, dozens of species show
off their full glory. Even a tree in your yard is probably
decorated with a good variety. After a rain, take a hand lens
to look up close. There’s an amazing, delicate and wonderful
little garden on nearly every branch. ó
Cladonia macilenta (called Lipstick Powderhorn by some!) has a
red ascocarp, a part of a lichen that bears spores.
Special thanks to Bruce McCune, Professor, Department of Botany
& Plant Pathology at OSU, for assistance with lichen identification.
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 4
by Don Boucher, photography by Lisa Millbank
T
he Red-tailed Hawk’s voice has been made famous
by TV and movies because it’s the voice double for
the Bald Eagle. The actual sound of a Bald Eagle
is a gull-like chatter, perhaps unsuitable for a glamorous
movie role. So, millions of people think an eagle screams
fiercely, but this call is unique to the Red-tail.
Red-tailed Hawks are year-round residents in Central
America, Mexico, the contiguous United States, the
Caribbean and parts of southern Canada. Throughout the
rest of Canada and parts of Alaska, they’re summer visitors.
They don’t go as far north as the arctic tundra.
Winter is a great time to go looking for Red-tails. While
they’re year-round residents in the Willamette Valley, some
Red-tailed Hawks from north of our region migrate here for
the winter, especially young birds. Red-tails are commonly
observed during hawk migration counts at Bonney Butte
(near Mt. Hood). The Willamette Valley is such an excellent
place for Red-tails to spend the winter, that it’s easy to spot
several perched along any highway through open country.
A typical adult western Red-tailed Hawk in flight shows a dark belly
band and dark bars at the leading edge of the wings.
red tails; instead their tails are banded with shades of brown.
Young and adult birds exhibit the typical field marks: a dark
hood with a dark throat, a pale or rusty, streaky breast with
a darker band across the belly, contrasted with a pale area
below the band. Perched birds have a mottled “V” pattern
All year round, Red-tails are some of the most common on the back. While soaring, the leading edge of the wing,
birds of prey. They’re in the genus or patagial bar, is much darker than the rest of the wing.
Buteo, a group of hawks with a This is a trait that distinguishes Red-tails from all of our
robust build, a short tail and broad other birds of prey. In dark
wings with rounded tips. The Red-tails, these features may
scientific name Buteo jamaicensis be obscured.
refers to Jamaica because Red-tails
were first described scientifically
Red-tails are so successful,
from Caribbean specimens. There in part, because they eat such
are more than a dozen subspecies a wide variety of prey. Most of
A perched adult Red-tail that vary in appearance.
the time, Red-tails hunt small
rodents in open areas. Usually,
It can be tricky to identify a Red-tail. In the Willamette they perch in a tree, utility
Valley, we only have to concern ourselves with the western pole or fence post, and pounce This adult Red-tailed Hawk is
subspecies, B. j. calurus. Other subspecies turn up only rarely. when prey is spotted. Any relatively dark.
Red-tails resemble other buteos, like the Red-shouldered prey will do; snakes, rabbits,
and Rough-legged Hawks. With a little investigation of lizards and sometimes insects
several key features, you can distinguish most Red-tails form are on the menu. Individual
other birds of prey (see illustration on page 7).
hunting preferences vary,
and sometimes Red-tailed
Though individuals vary a lot within western Red-tailed Hawks in adjacent territories
Hawks, they’re generally darker than most subspecies. In all may hunt different prey.
color phases, the top of the adult’s tail is rusty-red. While a One hawk may specialize
hawk is soaring on a sunny day, the rusty color shows from in snakes, while the other
A dark-morph young Red-tail
underneath. Birds younger than two years of age don’t have catches squirrels.
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 5
 This juvenile
Red-tailed Hawk
and the adult on the
lower left exhibit the
mottled “V” shaped
pattern on the back.
This pattern is
characteristic of
Red-tails.
 Of course, adult
Red-tails are easy
to identify when
you can see their
red tails. This was
a hard-won photo.
Most adult Redtails are wary and
hard to approach
close enough for a
good photo.
Females are, on average, significantly larger than males.
Hawks share this sexual dimorphism with many other
raptors and unrelated carnivorous birds like owls. The
reason for this isn’t altogether clear to science, but several
hypotheses exist. Here are two that seem the most plausible
to me. Different sizes lead to different prey selection.
This reduces the competition between a breeding pair
and increases their success occupying the same territory.
Predatory birds are aggressive and dangerous to each other.
Supposedly, if she is dominant, it may also lead to a more
peaceful and productive courtship and nesting relationship.
 A female Northern Harrier is brown
like a Red-tailed Hawk, but has a slender
body, long wingtips and a long tail. She
also has a unique facial disc.
 This Roughlegged Hawk has a
light-colored head
and breast, which is
typical of juveniles.
Most all Roughleggeds have pale
tails with a dark
terminal band.
 Red-shouldered Hawks have a tail
with broad, dark bands and narrow
white bands. This one is a juvenile.
The mottled pattern on the back is more
uniform than on Red-tails, which gives
them a somewhat “checkered” pattern.
Life for a young
hawk is hard.
Learning to hunt is
difficult, and nearly
half die of starvation
within their first year.
This is probably why
more young birds
migrate south. They’re
less savvy hunters in
cold, frozen northern
winters. In addition
Red-tails are monogamous and may keep the same mate to that, they have no
for years. You may see their courtship ritual, usually in late established breeding
winter and spring. They soar together in circles, sometimes territory to protect.
You can see the fuzzy, pale chick to the
crisscrossing, and may make stooping dives or briefly lock
talons. They dangle their legs and make a whistle-like call
Next time you hear right of the adult. This nest is lined with
that is different from their typical scream. I think it sounds that piercing scream fresh greens. You can see the browned
like an Osprey.
on TV or a movie, leaves of older linings.
you’ll know who the
Both male and female build a nest in a tree (or on a cliff real star is. Go brush elbows (or wing feathers in this case)
or tall building if necessary) with sticks, lined with bark with the bird whose voice is behind the fame. Although
strips or fresh greens. The greens are renewed throughout common, Red-tailed Hawks are respectable, fascinating
nesting. It’s common for them to start nest-building using and worthy of a second look. ó
a base of a previous nest or an abandoned nest of another
large bird like a Great Horned Owl, Great Blue Heron,
Listen to and watch a video of
raven or crow. Both sexes incubate the 2 or 3 eggs for about
Red-tailed Hawks at
30-35 days. The chicks hatch on different days. It takes
www.neighborhood-naturalist.com
about 45 days for the youngsters to fledge.
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 6
Soaring Raptor Comparison
Bald Eagle
Red-tailed Hawk
Turkey Vulture
Northern Harrier
“tippy” soaring pattern
juvenile
western subspecies
strong
dihedral
flat dihedral
strong dihedral
shallow
dihedral
Red-tailed Hawk
dark
patagial bars
Cooper’s Hawk
Peregrine Falcon
shallow
dihedral
flat
dihedral
flat
dihedral
relative sizes shown
dark hood
and throat
Rough-legged Hawk
adult male
winter only
brown tail
with dark
brown bars
belly
band
shallow
dihedral
dark, heavy
wrist marks
or “commas”
flat dihedral
Red-shouldered Hawk
juvenile
California and Oregon
subspecies
faint tail banding with
dark terminal band
tail has broad brown
bands and contrasting
narrow bands
well-defined,
contrasting
wing bars
Rough-legged Hawks
are often paler than
our Red-tails, but
occasionally they’re
very dark.
Neighborhood Naturalist, Winter 2010-11 v8 #4 • page 7
wing tips
longer than
Red-tailed
Hawk
illustration by Don Boucher
rusty
coloring
Owl Night
RSVP required
Saturday, January 8, 4:30 - 8pm
Join us at Willamette Park in Corvallis in search of
owls. An owl field trip is a real “shot in the dark,” and
we may not find any owls at all. But, if we’re lucky, we
could get multiple species. In winter, Willamette Park
can be home to the following owls: Great Horned Owl,
Western Screech-Owl,
Northern Saw-whet
Owl, Barn Owl and
Barred Owl. It’s much
more likely we’ll just
hear owls rather than
actually see them. We’ll
try calling to the owls
with human imitations
or recordings to get a
response.
Barn Owl
In this issue:
Lichens
Neighborhood Naturalist
5008 Technology Loop #9
Corvallis, OR 97333
photos by Lisa Millbank
Alternate date (in case of bad weather on January 8th):
Saturday, January 22, 4:30 - 8pm
Barred Owl
We may spend a lot of time standing around in
the darkness in freezing temperatures, depending
on the weather. Make sure that you have adequate
cold-weather clothing if you’d like to come. If the owl
activity is low or a total bust, we’ll still enjoy nature
at night and poke around for things like glowworms.
Please RSVP by Wednesday, January 5; space
is limited. We’ll contact you if the field trip is
postponed to the alternate date.
E-mail: [email protected]
Phone: 541-753-7689
Red-tailed Hawk
Events
Naturalist Adventures
Third Sunday of the Month, 9am-Noon
Jan 16 - Feb 20 - March 20 - Aptil 17 - May 15 - June 19
All trips meet at Avery Park Rose Garden: 1210 SW Avery Dr., Corvallis
Tracking - Wild Edibles - Native Plants - Birding
Our nature walks are slow-paced and casually structured. Bring along a hat, rain gear and shoes
that can get muddy. Please, no dogs. Activities are geared toward adults but children may enjoy
them too.
Bad weather: Rain, snow or cold will not prevent us from going out and enjoying nature. Remember
to dress for the rainy and/or cold weather. If conditions are dangerous for road travel (like icy roads)
trip may be canceled.
for more information: Don Boucher, 541-753-7689, [email protected]
www.neighborhood-naturalist.com
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