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Ecological Relationships of Desert Fog Zone Lichens
Author(s): Philip W. Rundel
Source:
The Bryologist,
Vol. 81, No. 2 (Summer, 1978), pp. 277-293
Published by: American Bryological and Lichenological Society
Stable URL: http://www.jstor.org/stable/3242189
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The
Bryologist
81(2),
1978,
pp.
277-293
Copyright ?
1978
by
the American
Bryological
and
Lichenological
Society,
Inc.
Ecological
Relationships
of
Desert
Fog
Zone Lichens1'3
PHILIP
W. RUNDEL2
Abstract.
Patterns
of
environmental conditions
prevailing
in
coastal
desert
fog
zones
provide
habitats
extremely
favorable for
lichen
growth. Phylogenet-
ically
related
groups of
lichens occur
in
geographically
isolated desert
fog
zones,
but endemism at
both
the
species
and
genus
levels is
relatively high.
The
ecological importance
of
lichens
in
these
regions
is
related to
morpholog-
ical and
physiological
adaptations
to water
uptake
in
both
a
liquid
and
vapor
form.
Much
of
this moisture is unavailable to
vascular
plants, allowing
a
large
biomass
of
lichens to
occur
in
areas with little or no vascular
plant
cover.
The
relative
importance
of fruticose
lichens
in such
habitats,
in
comparison
to
crustose and
foliose forms,
is
determined
largely by
the
physical form of
at-
mospheric
moisture.
Coastal
deserts
share
many
environmental
features
common to
all
deserts.
Rainfall
is
low and
vegetation
is
commonly sparse
or
lacking.
At
the same
time,
coastal deserts
have certain
distinctive characteristics not
shared
by
inland deserts.
Temperature
differences between
night
and
day
are moderated
by
the
proximity
of the
sea. More
important
for
lichens, however,
is the
typical
occurrence
of
high
atmospheric
humid-
ity, fog
and/or dew
along
the
coast.
Extensive coastal
deserts
occur
in
three
areas
of the world:
the
Peruvian
and
Chi-
lean
Atacama
deserts,
the coastal Sonoran Desert
in
Baja
California
and
the Namib
Desert
in
southwestern Africa.
Each
of these areas shares
the same
origin
of
climatic
development
in
the
movements of
sub-tropical high
pressure
centers
resulting
in
the
transport
and
upwelling
of cold currents
adjacent
to
their coasts. Details of
the
general
climatology
of these
regions
has
been described
in
many publications (e.g. Meigs,
1966;
Rumney, 1968).
Each of these
coastal
fog
deserts
is
characterized
by
lichen
floras rich
in
both
diversity
and biomass. This review describes the
ecological
and
floristic
relationships
of lichens
in
these coastal
fog
deserts with
particular
emphasis
on
the
coastal Atacama
and
Baja
California
regions.
Coastal Atacama Desert.-The
Atacama
desert
along
the
coasts
of Peru and north-
ern
Chile,
perhaps
the driest
region
in
the
world
in
terms
of
measurable
precipitation,
extends from
the
region
north of
Trujillo
near the Ecuadorian border
of
Peru
(50?S)
south to La Serena
(30?S)
in
Chile,
a total distance of more
than 3500 km.
Along
this
belt
is a
narrow
strip
of coastal desert whose
biological
characteristics are
profoundly
influenced
by frequent
maritime
fogs.
The cold northward
flowing
Humboldt
current
1
This
research
was
supported
by
NSF
grants
GB-40509 and DEB-75-19848.
I
thank Professors
Otto L.
Lange,
Ludger
Kappen
and Thomas
H. Nash for
helpful
discussion.
2
Department
of
Ecology
and
Evolutionary Biology, University
of
California,
Irvine,
CA
92717.
3
Part
of
symposium
on "The
Role
of Lichens
in
Ecosystems,"
Second
International
Myco-
logical
Congress.
Tampa, Florida,
U.S.A.
Aug. 27-Sept.
3,
1977.
0007-2745/78/277-293$1.95/0
THE BRYOLOGIST
1000-
800-
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< > ;.01^
.**.
:
"'.^
.* cZ
*(
0of
perennials
2
200-
/
cryptograms
/
_'
no
vegetation
0-
j-,ansia
FIGURE
1.
Diagrammatic
view of
vegetation
zonation
in
the coastal
lomas
of
Southern Peru.
Redrawn
from
Ellenberg
(1959).
and
associated
areas
of
extensive
upwelling
of
deep
ocean
waters
off
the
Atacama
Coast
produce
a
mild,
uniform
climate
in
the
coastal
zone and
such
stable air
mass
conditions that
precipitation
is rare
or
even
absent. In
the
coastal
Chilean
Atacama,
mean
annual
precipitation
ranges
from
a
high
of
26 mm
at
Caldera
to an
incredible
0.6 mm
at
Arica over
a 44
year
record.
In
central Peru
precipitation
increases
slightly,
reaching
41
mm
yr-1
at
Lima.
Available
climatological
atta
for
the
Atacama
desert
has
been
detailed
by
Hajek
and di
Castri
(1975)
and di
Castri
and
Hajek
(1976).
Less
data
are
known for coastal
Peru,
but
available records
are
summarized
by
Meigs
(1966).
A
summary
of
climatic
data
for
selected coastal
stations
is
shown
in
Table
1.
Although
precipitation
is
slight,
water
input
from
moisture
condensation from
coastal
fogs
allows local
development
of rich
biological
communities. Thick
low
fogs,
termed the
garua
in
Peru
and the
camanchaca
in
Chile,
form
along
the
coast almost
daily
during
the
winter
season
from
June
to
October.
Although
the
elevational
limits
of
the
garua
and
camanchaca
vary
somewhat
with
latitude
and
local
topography,
fog
is
typically
present
in
a
well-defined
band
extending
from
300-800 m
(Rundel
&
Mahu,
1976).
Where
the
coastal
topography
is
low
and
relatively
flat,
the
effects
of
the
fog
are
dissipated
over
broad
areas
with
little
resultant
biological
influence.
Where
steep
coastal
mountains
are
present,
however,
fog
condensation
is
concentrated
in
a
narrow
belt
where
moisture
input
allows
the
development
of
relatively
lush
fog
zone
vegetation.
Coniin
rnditions
for
conensation
of
fog
moisture
are
particularly
favorable
along
the
tt(ener
e temertu
othe
Atacama
coast
(Ellenberg, 1959).
The
temperature
of
the
Humboldt
Current
is
warmer
than
that
of
similar
currents
off the
coasts
of
Baja
California
and
Namibia,
producing high
water
vapor
contents
and
consequently high
aerosol
liquid
water
con-
tent
of air
masses with
subsequent
cooling.
Also
important
is the
constant
light
south-
west
winds,
blowing
onshore at
velocities
up
to 4
m/s.
This wind
is
important
in
providing
a
continuing
source
of
new
aerosol
water
for
condensation
against
the
steep
coastal
mountains.
Vegetation
development
in
the
coastal lomas
of
Peru
has
been
described
by
many
(e.g. Troll,
1932;
Weberbauer,
1945;
Ellenberg,
1959;
Koepcke,
1961;
Walter,
1971).
A
diagrammatic
representation
of a
typical
coastal
fog
zone
is
shown in
Figure
1.
The
coastal
plain
below
thoone
fog
zone
is
barren of
vegetation,
except
for
scattered stands
of
unrooted
terrestrial
Tillandsia
(Bromeliaceae)
which
occurs
on
windblown sand
278
[Volume
81
RUNDEL: DESERT FOG ZONE LICHENS
TABLE 1. Climatic data
for coastal stations
in
the Atacama Desert of
Peru and
Chile,
Sonoran
Desert
on
the Pacific Coast of
Baja
California
and
Nanib Desert of
Angola,
Namibia
and
South
Africa.
Data
from
Meigs
(1966),
di Castri
and
Hajek
(1976)
and
Hastings
and
Humphrey
(1969).
Mean Mean Mean
Mean
Annual Annual Annual
Eleva-
Annual Max.
Min.
Precipi-
Years
Latitude
tion
Temp. Temp. Temp.
tation of Prec.
(?S
or
?N)
(m)
(?C) (?C) (?C)
(mm)
Records
Atacama-Peru
Lambayegue
Chiclayo
Trujillo
Lima
Mollendo
Atacama-Chile
Arica
Iquique
Los
Condores
Cerro
Moreno
Taltal
Chafiaral
Caldera
La
Serena
Sonoran-Baja
California
Isla
Todos
Santos
San Telmo
El
Socorro
El
Rosario
Vizcaino
Bahia
Tortugas
Punta
Abreojos
San
Juanico
Bahia
Magdalena
La
Aguja
Todos Santos
Namib
Luanda
Lobito
Mocamedes
Walvis
Bay
Port Nolloth
Klaver
6037'
6?41'
8005'
1200'
17?58'
18?28'
20?12'
20015'
23?29'
25?25'
26020'
27?03'
29054'
31048'
30058'
30020'
30004'
27059'
27042'
26?44'
26?16'
24038'
23059'
23026'
8050'
12?13'
15?10'
22053'
29010'
31043'
5
19
49
7
29
515
518
119
39
9
28
32
22
100
10
15
10
5
15
12
12
10
18
60
1
3
7
7
42
22.2
21.1
18.9
17.8
18.7
17.9
15.5
17.0
17.4
16.4
16.1
14.8
16.3
16.9
20.9
18.8
20.3
21.6
21.1
21.4
22.4
22.0
24.4
24.4
21.1
17.2
13.9
19.4
22.9
15.2
27.9
23.9
16.1 45.7
19.4
16.1 22.1
22.2
21.2
19.0
20.1
22.0
19.3
19.7
18.9
15.1
14.1
10.2
13.3
14.5
12.2
12.9
11.2
0.6
2.1
0.0
2.2
25.1
1.7
25.8
127.4
255.6
172.1
137.7
95.0
79.8
95.8
76.8
64.1
73.7
49.9
169.6
27.2
27.2
25.0
22.2
18.3
26.7
21.7
21.1
16.7
11.7
9.4
12.2
322.6
353.1
53.3
22.9
58.4
dunes. The lower
margin
of the
fog
zone
is
characterized
by
cryptogamic
communities
of
Nostoc and
Teloschistes on stable
sand surfaces
and
crustose
lichens on
rock sub-
strates.
Higher
up,
scattered stands of herbaceous
plants
and low
woody vegetation
merge
into a
true
fog
forest of
evergreen
trees
5-8
m in
height
at the
center
of
the
fog
zone.
Epiphytic
mosses
and lichens are abundant.
As the
density
of the
fog
zone
decreases at
700
m,
open
stands of
vegetation
give
way
to scattered
cacti
and
tillands-
ias
and,
finally,
to barren land free of
plants. Ellenberg
(1959)
found
that
vascular
plant
development
over the
fog
moisture
gradient
was related
to the
depth
of
pene-
tration of soil
moisture.
Virtually
no
data are available on
lichen
zonation,
however.
Vegetation
zonation
in
the
coastal
fog
belt
of northern
Chile at
Paposo
has been
described
in detail
by
Rundel and
Mahu
(1976),
and
broadly by
Reiche
(1911)
while
8
3-4
2-4
26
13
44
49
7
7
21
7
49
91
7
17
11
14
10
11
12
8
31
5
30
59
19
21
20
64
279
1978]
280
THE BRYOLOGIST
[Volume
81
-1000
NO
/o
^/VEGETATION
. . . . .. . . . . . . . .
. . . . . . . . . . . . . .
. . . . . ..
.
. o
o
/
........'.......'--
--
COPIAPOA
:....:::::: :::::::::::::::::::::::::::...............
-800
................................ ...
uo
X
o
.. .. ..
..
.. ..
EULYCHNIA-
... .. . ..
.................. .-..-.---.
-*
S
/
COPIAPOA
.
. . .
. .
. . . . .
.
. .
. . . .
. . . . .
. . .
.
. .
. .
. . .
. . .
.
. .
. .
.*
n
.
'
iS
...*.
....
........
...........(J........
...l
r?
m
FO^^^G
^<I
1
-600 r
:*:*
EUPHORBIA-
-
..
. .
.
.
.
. ....
. . . .
.
.
. . . . .
..
.
.
.
.........................
EULYCHN IA
o
z
~~0~~~~~ ~-400
^^
**--:---------.-.-.-.-
.
--EULYCHNIA-
PUYA
0
0o
'-200
<6O 0
/ OPEN COASTAL PLAIN-COPIAPOA
-
0
-~~~~~~~~~~~~0
FIGURE
2.
Diagrammatic
view of
vegetation
zonation
in the
coastal
fog
zone
at
Paposo,
Atacama
Province,
Chile. From Rundel
and Mahu
(1976).
the
flora
of
this zone has been treated
by Johnston
(1929).
Here the coastal
plain
below the
fog
belt
supports
scattered
stands of small
globular
cacti
grading
to
a distinct
belt of terrestrial
Puya
(Bromeliaceae)
at the lower
margin
of the
fog
zone
(Figure
2).
Within the
central
fog
zone,
woody vegetation
becomes
dominant
in
forming
dense
stands 2-3
m in
height
with
60%
ground
cover. At
higher
elevations
in
the
upper
fog
zone,
open slopes
with
increasingly
scattered
cacti
replace woody vegetation
(Rundel
&
Mahu,
1976),
with the
area above 1000
m
virtually
free of
any
vegetation.
While
the
development
of
woody
vegetation
is not
as
luxuriant as
in
the lomas
of
Peru,
the
diversity
and
biomass
of
lichen
epiphytes
are
greater.
Detailed studies
of
the
lichen
flora
of
the
coastal
Chilean
zone
have been made
at
Cerro Moreno
near
Antofagasta
(Follmann,
1960, 1967c),
at
Paposo (Rundel,
unpublished
data)
and
at
the desert-
sclerophyll
transition
zone of
Coquimbo
and
Aconcagua
Provinces
(Follmann,
1960;
Follmann &
Redon,
1972; Redon, 1972).
Coastal Sonoran Desert
of
Baja California.-The
coastal Sonoran
Desert extends
from El
Rosario south
along
the
Baja
California
peninsula.
Coastal
fogs
and
high
humidity, extending
as
much as
50
km
inland,
are characteristic of
this desert area
as
well as semi-arid
sclerophyll
and thorn
forest
vegetation
transitions
on the
north-
western coast and southern end of the
peninsula.
The
general vegetation
character-
istics and vascular
plant
flora
of
this
desert
region
were described
in
detail
by
Shreve
and
Wiggins
(1964).
Extensive
climatological
data
for
Baja
California have also
been
published
(Hastings,
1964;
Hastings
&
Humphrey,
1969).
Data
for
coastal
stations are
summarized in
Table
1.
Unlike the
South
American coastal
desert
region,
no distinctive
fog
zone forms
along
the coast of
Baja
California.
While
fogs
are common
along
the
coast,
they
lack
the
temporal
and
structural
regularity
of the
garua/camanchaca.
Winter
fogs
are
par-
ticularly
common,
occurring
down to sea
level,
and moist
marine air close to
moisture
saturation blows
strongly
onshore
throughout
the
year. Contrasting
with the
gentle
RUNDEL: DESERT
FOG ZONE LICHENS
but
steady
onshore
winds
characteristic of the Coastal
Atacama,
strong
irregular
winds
blow off of the Pacific Ocean
in
Baja
California,
stunting
vascular
plant
vegetation
along
the
coast
and
frequently continuing
only
slightly
abated
up
to 20
km
or
more
inland.
Steep
topographic
features
are
rare
along
the
Baja
California
coast,
allowing
maritime influences to reach well
across
the
peninsula
in
both the
central Vizcaino
Region
and the
Magdalena
Plain
(Shreve
&
Wiggins,
1964).
Moisture
condensation
from humid
air masses
and
irregular
fogs
allow the
development
of a
moderately
diverse
epiphytic
lichen
community
(Nash
et
al., 1977)
and a
locally
dense
growth
of
Tillandsia recurvata
on
a
variety
of shrubs and
succulents.
Although
true
coastal
fog
belts do
not
form
along
the coast of
Baja
California,
distinctive
vegetation
zones dominated
by
lichens
develop
where
steep
cliffs on mod-
erate
slopes
are
topographically developed along
the immediate coast
(Rundel
et
al.,
1972).
Vascular
plant
vegetation
is
commonly
restricted
severely
in
these habitats
by
soil
aridity,
wind
desiccation and salt
spray.
Local conditions are
optimal,
however,
for luxuriant
growth
of
epiphytic,
saxicolous
and terricolous
lichens,
and lichen
bio-
mass
may
rival or even
surpass
that of vascular
plants
in
these coastal areas.
Although
published
studies of the floristics and
ecology
of
lichens
in
this
coastal
zone
are few
(Rundel
et
al.,
1972;
Nash
et
al.,
1977;
Dodge,
1936),
the lichen flora
is
relatively
well
known.
Namib
Desert.-The
Namib Desert stretches
along
the southwest coast of
Africa,
extending
2800
km
from Luanda
(8?45'S)
in
Angola
to St. Helena
Bay
(32?45?S)
in
South
Africa
(Meigs,
1966).
Like the
deserts
of
Baja
California
and the
coast
of Peru
and
Chile,
the coastal Namib
is
characterized
by
cool,
moist sea
fogs, resulting
from
the cold
Benguela
Current.
Observations
at
Luderitz
Bay
showed 285
days during
the
year
with
fog
or
dew
(Meigs,
1966).
Even when there is
no
fog,
relative
humidities
remain at 100
percent
during
most of the
day.
Surface condensation of
this
water
is
the
major
source of moisture for an extensive lichen
flora,
as well
as
for
several unusual
succulent
plants
(Walter,
1971; Giess, 1962;
Bornman et
al.,
1973).
Annual
precipi-
tation is
commonly
in
the
range
of
only
20-50
mm
along
the coast.
Although
several
general
discussions
of the environment and
vegetation
of the Namib Desert
are avail-
able
(Cannon,
1924;
Logan,
1960; Walter, 1936, 1971),
detailed
descriptions
of
the
flora
are
scarce
(Giess,
1962,
1968).
Vascular
plant
adaptations
have
been
discussed
by
Schulze and Schulze
(1976)
and Schulze et al.
(1976).
The lichen flora of
this
area
has not
been
described.
Level,
gravelly
desert
plains
of the outer
Namib
support only
rare individuals of
vascular
plants,
but
the windward sides
of
even
small
pebbles
have
well-developed
lichen
growth.
This
growth,
dominated
by Caloplaca,
occurs
both as
upright
subfo-
liose
morphotypes
which take
advantage
of direct
fog interception
and
small crustose
growths
at soil level which utilize runoff from
fog
condensation
on the rock above.
A
variety
of
strange
specialized
lichen
growth
forms from the
southern
Namib
were
described
by
Vogel
(1955).
Farther
inland,
dense colonies
of
Teloschistes
form a
dis-
tinct
stabilizing
element
on
low sand
dunes,
comparable
to the zone of
T.
peruensis
in
southern
Peru.
The
windward
slopes
of
quartzite
and
marble
ridges
in
nearby
areas
provides
vertical
faces where
fog
condensation
may
become
concentrated.
A
variety
of
both
stem
and leaf succulent
plants
dominate
these
slopes,
together
with a
rich
saxicolous lichen
flora
(L.
Kappen, pers.
comm.).
FLORISTIC COMPARISONS
Despite
the
wide
geographic separation
of the three
major regions
of desert
fog
zones,
considerable floristic similarities exist
among
the lichen floras of these areas.
1978]
281
THE
BRYOLOGIST
TABLE
2.
Occurrence
of
species
of Roccellaceae
in
the
coastal
fog
deserts of
Baja
California
and
Chile. Data
from
Rundel et
al.
(1972),
Follmann
(1967c),
Follmann
& Redon
(1972)
and
Rundel
(unpublished
data).
Baja
California Chile
Crustose
Dirina
catalinariae Hasse Dirina chilensis
(Nyl.)
Follm.
D.
limitata
Nyl.
D.
lutosa
Zahlbr.
Dirinastrum chilense
(Dodge)
Follm.
Lobodirina
cerebriformis
(Mont.)
Follm.
L.
mahuiana
Follm.
Fruticose-Foliose
Darbishirella
gracillima
(Kremph.)
Zahlbr.
Dendrographa leucophaea
(Tuck.)
Darb.
Dolichocarpus
chilensis
Sant.
Ingaderia pulcherrima
Darb.
Pentagenella
fragillima
Darb.
Reinkella
parishii
Hasse
Reinkella
lirellina Darb.
Roccella
babingtonii
Mont.
Roccella
babingtonii
Mont.
R.
fimbriata
Darb. R.
cervicornis Follm.
R.
sp.
R.
gayana
Mont.
R.
minima Sant.
R.
portentosa
(Mont.)
Darb.
Roccellaria mollis
(Hampe)
Zahlbr.
Roccellina condensata
Darb.
R.
luteola Follm.
Schizopelte
californica
Th.Fr.
However,
unlike
dry
desert
floras of terricolous
and
saxicolous
lichens,
where
indi-
vidual
species frequently
have worldwide
distribution
patterns
(Weber,
1962),
the
floristic
similarity
of desert
fog
zones
is
primarily
evident at the
family
and
genus
levels.
All
three desert
fog
zone
regions
are dominated
by
species
of Roccellaceae
on
coastal
rocks,
where aerosol
moisture
input
is
high.
The
diversity
of
species
is
variable
between
regions,
however.
At Cerro Moreno
near
Antofagasta
in
northern
Chile,
19
species
of
Roccellaceae
in
12
genera
are
present
(Table
2).
At a
comparable
site
in
Baja
California,
only
seven
species
in five
genera
are
present,
although
the
total
bio-
mass of Roccellaceae
is
greater
(Rundel, unpublished
data).
Despite
the differences
in
diversity
between
species
in
the Roccellaceae
between
Baja
California
and
Chile,
the
relative occurrence
of
species
on
different substrate
types
is
remarkably
similar.
In
Baja
California,
33% of
the
species typically
occur
on
vascular
plant
substrates,
while the
remaining
67%
are
on
rock.
In
Chile,
37%
are
on
vascular
plants,
58%
on
rock
and 5% on soil.
Genera of the
Roccellaceae,
hypothetically
very
old
taxa,
are
today
commonly
geographically
isolated.
Coastal desert
fog
zones
where
these
endemic
genera
are
concentrated,
however,
are
geologically
recently
formed.
Recent
isolation of
geno-
types
does not
appear
to be an
important
consideration
in
speciation,
and
therefore
diversity,
in
either
Chile or
California/Baja
California.
The
majority
of
species
have
a wide latitude of occurrence
in
coastal habitats.
A notable
exception
to
this
pattern
282
[Volume
81
RUNDEL: DESERT FOG
ZONE
LICHENS
TABLE
3.
Occurrence of
species
of Ramalinaceae
in
the
coastal
fog
deserts
of
Baja
Cali-
fornia
and Chile.
Data from
Rundel et
al.
(1972),
Follmann
(1967c),
Follmann and Redon
(1972),
Redon
(1972)
and
Rundel
(unpublished data).
Baja
California
Chile
Cenozosia
inanis
Mont.
Niebla
cephalota
(Tuck.)
Rund. & Bowl. Niebla
cephalota (Tuck.)
Rund.
&
Bowl.
N.
ceruchis
(Ach.)
Rund. & Bowl.
N.
ceruchis
(Ach.)
Rund.
&
Bowl.
N.
homalea
(Ach.)
Rund. & Bowl.
N.
flaccescens (Nyl.)
Rund. &
Bowl.
N.
josecuervoi
(Rund.
&
Bowl.)
Rund. & Bowl.
N.
tigrina
(Follm.)
Rund.
& Bowl.
N.
pulchribarbara
(Rund.
&
Bowl.)
N.
sp.
nov.
Rund. & Bowl.
N.
robusta
(Tuck.)
Rund. &
Bowl.
N.
sp.
nov.
N.
sp.
nov.
N.
sp.
nov.
Ramalina
bajacalifornica
Bowl.
& Rund. Ramalina
chilensis
Bert.
R.
complanata
(Sw.)
Ach.
R.
duriaei
(DeNot.)
Jatta
R.
denticulata
(Eschw.) Nyl.
R.
dusenii
Magn.
nom.
nudum
R.
duriaei
(DeNot.) Jatta
R.
ecklonii
(Spreng.)
Mey.
&
Flot.
R.
farinacea
(L.)
Ach. R.
peruviana
Ach.
R.
leptocarpha
Tuck.
R.
sulcatula
Nyl.
R.
menziesii
Tayl.
R.
terebrata
Hook. &
Tayl.
R.
moranii
Rund. & Bowl.
R.
sp.
R.
subleptocarpha
Rund. &
Bowl.
R.
wigginsii
Rund. &
Bowl.
R.
sp.
nov.
Trichoramalina
crinita
(Tuck.)
Rund. &
Bowl.
is
Hubbsia,
restricted to a
single
rock
outcrop
on
Guadeloupe
Island,
an oceanic
island
off the
coast
of
Baja
California
(Weber,
1965). Only
two
species
of
Roccellaceae,
both
Roccella,
are shared
between
Baja
California
and
Chile
(Table 2).
One
of
these,
R.
babingtonii,
is a sorediate
species
whose wide
distribution
is
in
all
three
desert
fog
regions.
This is consistent
with the
hypothesis
of
relatively
great dispersability
and
establishment
of sorediate
forms
(Bowler
&
Rundel, 1975).
Three
genera,
Roccella,
Reinkella
and
Dirina,
occur
in
both
regions,
while
eight
genera
are endemic
to
Chile
and three to
California-Baja
California.
A
single
endemic
genus
of
Roccellaceae,
Com-
bea,
is known
from the Namib
Desert. Numerous
species
of
Roccella
are
present,
however.
A
second
important family
of desert
fog
zone lichens
is the Ramalinaceae.
As
in
the
Roccellaceae, however,
few
species
are shared
between
regions.
Only
Ramalina
duriae occurs
in
all three
regions.
Two
species
of
Niebla
are shared
between
Baja
California and
Chile,
and
a
single
species
of
Ramalina
is
present
in
both
Chile and
the
Namib.
This is
a
very
small
species
similarity
in view of the
high
diversity
of
Ramalinaceae
in
all three
regions.
Opposite
to
the
situation
in
the
Roccellaceae,
the
diversity
of Ramalinaceae
is
greater
in
Baja
California than
in
Chile
(Table
3).
Three
genera
and
20
species
of
Ramalinaceae are characteristic
in
this
zone
of
Baja
California,
including
Trichora-
malina which is absent
from Chile.
Three
genera
and 12
species
are
present
in
Chile,
including
the
endemic
Cenozosia. For
Baja
California,
62%
of
these
species
are
cor-
ticolous,
with the
remaining
38% on saxicolous
or terricolous
substrates.
This latter
group, including
the
majority
of taxa of
Niebla,
are
extremely
prominent
and
locally
283
1978]
THE
BRYOLOGIST
produce
large
biomasses
in
the immediate coastal zone where aerosol
moisture
is
high.
Away
from
the
coast,
corticolous
Ramalina
is
dominant.
In
Chile,
saxicolous
and
terricolous habitats
for
Ramalinaceae are
relatively unimportant
although
28% of
the
species
are
typically
on
such
substrates.
Large
biomasses of
saxicolous taxa are
totally
absent.
Numerous
taxa
of Ramalinaceae
are
present
in
the Namib
Desert,
but
the
majority
of
species
of
Ramalina
are endemic and remain undescribed.
Trichoramalina
melanothrix,
with a related
species
in
Baja
California,
is
an
unusual endemic
(Rundel
&
Bowler,
1974).
A
third
family
which
forms
important
elements
of
desert
fog
zone
lichens is
the
Teloschistaceae,
most
notably
the
genus
Teloschistes. Four
species
of
this
genus
are
present
in
the
fog
deserts
of
both
Baja
California
and
Chile-T.
exilis,
T.
flavicans,
T.
chrysophthalmus
and
T.
villosus. The
latter is
typically
restricted
to
the immediate
coast,
while the others occur well inland.
As
previously
described,
the endemic
T.
peruensis
is
extremely important ecologically
on sand dunes at the lower
margin
of
the
fog
zone
in
Peru
(Thomson
&
Iltis, 1968).
The
Namib
Desert and
adjacent
parts
of South Africa are likewise characterized
by many
ecologically
important
species
of
Teloschistes.
The
unique
fruticose Xanthoria
flammea
is also restricted
to
this
region.
Many
other floristic elements
are
important
in all
of the
desert
fog
zone
regions.
Species
of Parmelia
with
upright growth-forms
occur
in
each
region
and
may
dominate
the flora
locally
as
with P.
hottentota
and
similar
species
on
rocky slopes
in
the
Namib.
Chile and
Baja
California are
alike
in the
frequent
occurrence
of ciliate
species
of
Heterodermia.
TRENTEPOHLIA
SYMBIOSES
An
unusually large percentage
of the lichen floras
of coastal
fog
zones of
Baja
California
and Chile
are
composed
of
species
with
Trentepohlia
as an
algal
symbiont.
Trentepohlioid
algae
are the
symbionts
in
such
ecologically
important fog
zone
genera
as
Roccella,
Dendrographa,
Darbishirella,
Dolichocarpus,
Hubbsia,
Pentagenella,
In-
gaderia,
Reinkella,
Dirina, Schizopelte,
Opegrapha
and
Coenogonium,
as well
as
in
a
variety
of less dominant crustose
genera
in
the
Pyrenulaceae,
Arthoniaceae, Ope-
graphaceae
and
Graphidaceae. Although
not well
investigated,
lichens
with trente-
pohlioid symbionts
are
also
ecologically
important
in
the
coastal
Namib
(L.
Kappen,
pers.
comm.).
Within
the macrolichen
flora,
only
Ramalina,
Niebla,
Usnea and
Het-
erodermia,
all with
Trebouxia,
rival the
ecological
dominance
of the
genera
with
trentepohlioid
symbionts.
There
is
considerable
controversy
in
the
lichenological
literature
concerning
the
biological
basis for
the
establishment of
symbioses
between
spores
of
lichenized
fungi
and Trebouxia. Since
Trebouxia
is
not
commonly
observed
free-living
in
nature,
the
source
of the
necessary algal
cells is
unclear,
and
yet
sexual
reproduction clearly
takes
place
with
fertile lichen
species
(Bowler
&
Rundel,
1975).
With
Trentepohlia,
how-
ever,
the
potential
source
of
symbionts
for lichenization can
be
easily
seen
in the
field.
Free-living
colonies of
Trentepohlia
are
common
on
both
rock and
plant
surfaces
in
both
the
Baja
Californian
and
Chilean
coastal
deserts.
Little
is
known
of
the
physiology
and
ecology
of
Trentepohlia.
The
characteristic
orange-red
color
results from 8-carotene dissolved
in
fat
deposits
(Geitler,
1923).
This
pigment hypothetically
relates to
the resistance
of
Trentepohlia
to
high
light
intensities.
In
shaded localities the
pigment
may
be almost
completely
lacking
(Fritsch, 1948).
With
full
pigmentation,
Trentepohlia
is
extremely
resistant to
high
insolation,
much more so
than
typical
green
and
blue-green algae.
Nevertheless,
many
[Volume
81
284
RUNDEL:
DESERT FOG ZONE LICHENS
TABLE 4. Relative
growth-form
distribution
of
warm
desert
lichen floras.
Lichen Growth-Form
(%)
Number
of
Crustose &
Species
Fruticose Foliose
squamulose
Interior Desert
Algerian
Sahara Desert
114 0
2
98
(Faurel
et
al., 1953)
Negev Desert,
Israel
44
5
2
93
(Galun,
1970)
Sonoran Desert
Rock
Valley,
California
17 0 12 88
(Nash
et
al.,
1977)
Silverbell,
Arizona
21 0 19
81
(Nash
et
al., 1977)
Maricopa
Co.,
Arizona
78 0
28
72
(Nash,
1975)
Chihuahuan Desert
Jornada,
New
Mexico
48
0
40
60
(Nash
et
al., 1977)
Coastal
Fog
Desert
Baja
California,
Mexico
67 54 13
33
(Rundel
&
Nash,
unpublished
data)
Cerro
Moreno,
Atacama 146 25
14
60
Prov.,
Chile
(Follmann, 1967b)
lichens with
Trentepohlia
appear
to be
very
tolerant
of
low
light
levels,
notably spe-
cies
of
Opegrapha,
Coenogonium,
Graphis,
Lecanactis and
Lepraria. Although
there
has been little
study
of
the
temperature
tolerances of lichens
with
Trentepohlia sym-
bionts,
there
is some
speculation
that
many
of
these
species may
be
sensitive to
cold
temperatures
(Kappen,
1973).
The
geographic
distribution
of
macrolichens
with
Tren-
tepohlia
is
consistent
with
this
hypothesis.
Plants
of
Trentepohlia
can withstand
long periods
of
desiccation
(Howland, 1929),
an
important
adaptation
for survival in the
variable
fog
conditions of coastal
deserts.
The
availability
of
colonies of
Trentepohlia
for
lichenization
is increased
by
its re-
productive
characteristics. It
commonly reproduces
vegetatively
by
wind-blown
frag-
ments,
although
it
may
also
reproduce sexually
with
swarmers
in
wet conditions
(Fritsch,
1948).
Cultural
experiments
utilizing
several
crustose
genera
of lichens have
shown that lichenization occurs
within
three to
six
weeks of the
time
after Trente-
pohlia
and
mycobiont
cultures
of
symbionts
were
placed
together
(Herisset,
1946;
Ahmadjian,
1973).
MORPHOLOGICAL ADAPTATIONS
Morphological adaptations
to
specific
environmental stresses are to
be
expected
in
lichens as well as
in
vascular
plants.
Such
adaptations
to
hot,
dry
desert environ-
ments include:
1.
increased cortical thickness under conditions of
high
light
intensity
(Vogel,
1955;
Galun, 1963;
Follmann,
1965;
Poelt &
Wirth, 1968);
2.
increased
prui-
nosity
or other
superficial layers
to
protect against high light
intensity
(Schulz,
1931;
Galun,
1963;
Poelt &
Wirth, 1968;
but see also
Weber, 1962);
and
3.
increased
relative
dominance of
crustose
growth
form
(Galun,
1970).
Under environmental conditions
1978]
285
THE BRYOLOGIST
in
desert
fog
zones,
however,
the structure
and
morphological
characteristics
of lichen
floras differ
greatly.
The most
significant
environmental factors
appear
to be moderate
temperatures,
high
atmospheric
moisture
content,
strong
winds and variable solar
insolation. Natural
selection should be
expected,
therefore,
to
favor
adaptations
for
optimizing
water
uptake,
reducing
desiccation rates
and
minimizing
mechanical dam-
age
due to wind.
Contrary
to the situation
in
hot,
dry
deserts,
fruticose
lichen
growth
forms
dominate
in
coastal
fog
deserts
(Table
4).
Crustose lichens
in
fact,
comprise
only
a small
per-
centage
of the total lichen
coverage
in
many
areas of
unusually
high
fog
frequency
in
both
Baja
California and
Chile.
It
appears,
therefore,
that the fruticose
growth
form
may
have selective value for
optimizing
moisture
uptake, provided
fogs
are
frequent
and
temperatures
moderate.
Morphological adaptations
to maximize
water
uptake
have
been
demonstrated
in
fog
zone lichens. The size
and structure
of reticulations
in
Ramalina menziesii
Tuck.
(=
R.
reticulata
Kremph.)
are related
to
frequency
of
fog
and
relative levels of
atmos-
pheric
humidity
(Rundel, 1974).
Morphological
variation related
to
fog
occurrence
in
Ramalina usnea
is
present
in
tropical
areas
(Rundel, 1978).
Desert
lichens
may
have
capabilities
of
accumulating
water
rapidly,
but
only
slow-
ly, losing
it
through
desiccation
(Zukal,
1896; Galun, 1963;
Follmann,
1965).
Blum
(1965, 1973), however,
rejected
the
significance
of
xeromorphic
adaptations
for
pro-
tection
against
evaporation. Experimental
studies
with
arctic and
subarctic
lichens
have
clearly
established that
morphological
characteristics
may
profoundly
affect
thal-
lus water
relations
(Larson
&
Kershaw, 1976).
Thallus surface to
volume
ratio,
branch
shape
and
degree
of
clumping
of branches
all influence
the
evaporative
resistance,
producing
significant
intraspecific
and
interspecific
population
variability.
These same
morphological
characteristics are
clearly
important
in
habitat selection
by
coastal
fog
zone
lichen taxa.
Saxicolous and terricolous substrates
in
coastal
fog
zones characterized
by
aerosol
liquid
moisture
input
are dominated
by
thallus
morphologies
which
expose
large
areas
of
branch surface
perpendicularly
to
the direct moisture-laden
winds. This
thallus
surface area
may
be
exposed
as flattened
branches
(Niebla
josecuervoi)
or
dense
clumps
of terete branches
(Niebla
"ceruchoides," Teloschistes
spp.).
Crustose
growth-
forms of lichens on
horizontal surfaces are
poorly
adapted
for moisture
uptake
from
aerosol sources. Fruticose
growth
forms
typically
dominate,
but
some
crustose
forms
are
ecologically
successful
on such surfaces
by
utilizing
morphological
adaptations
to
increase thallus surface areas
exposed
to
moist
winds.
Many
taxa
in
groups typically
crustose
become
virtually
fruticose,
forming
a
clumped
to
caespitose growth
form.
This
morphological
development
can be best seen
in
Caloplaca
coralloides
and Lec-
anora
phyganitis
in
the
California-Baja
California coastal
flora. Raised verrucae
in
coastal taxa
of Thelomma
may
represent
a similar
adaptation.
On
corticolous
substrates,
where moisture condensation
on
foliage
and
branches
produces
considerable available
water,
the
thallus
growth
form
is
less critical.
Char-
acteristically,
however,
thalli
are most
abundant well inside
shrubs rather
than on
small branches on the outer surface.
On
cacti
in
northern
Chile,
downward
pointing
spines
act as
major
condensation
foci
and
epiphytic
lichens are concentrated
near the
spine tip
rather
than on the aereoles. Pendulous or
tufted lichens near
the
spine tips
are
ideally
suited to
maximize
water
uptake
(Figure
3).
In
inland areas of
fog
zones where
major
moisture
input
is in a
water
vapor
form,
vertical
orientation
of thallus branches
is less
important
and foliose
and crustose
[Volume
81
286
RUNDEL:
DESERT
FOG ZONE LICHENS
:
:
;iiiii~: I
F
4~-
~
FIGURE
3.
Lichen
diversity
on
spines
ofEulychnia
iquiquensis
at
Paposo.
287
1978]
growth
forms increase
in
importance.
Total biomass
of
lichens
in
such areas
is rela-
tively
low,
however
(Kappen
et
al., 1975;
Nash
et
al., 1977).
Many
individual
morphological
characteristics of
lichen thalli
may
also be
impor-
tant
in
water relations.
Cilia
frequently
occur
in
taxa
of
desert
fog
zone lichens
(e.g.
Heterodermia,
Parmelia, Trichoramalina, Tornabenia).
Although
definitive
experi-
ments have
not
been
completed,
such
cilia
would be
expected
to have
adaptive
value
in
straining
aerosol
water
droplets
out of
humid
air.
Pseudocyphellae
and related
white
striations
(maculae),
present
in
many
taxa,
may
also relate to water
uptake.
These structures are
positively
correlated
with
populations
of
the Ramalina usnea
complex
from
foggy
microenvironments
(Rundel,
1978).
Thick
cortices are characteristic of
many
desert
fog
zone lichens
(Rundel
&
Bowler,
1974).
It is doubtful
if
this
adaptation
is
primarily
a
response
to
high
light
intensities
as
in
lichens
from
hot,
dry
deserts. More
likely,
cortical
thickness
is
largely
influenced
by potential
mechanical
damage
and
desiccation
by
wind.
Morphological
adaptations
to sand
blasting
in
Antarctica include the formation
of
a
cortex with thick-walled
hyphae closely appressed
(Dodge,
1965).
Such cortical
structure is characteristic
of
the
Ramalinaceae
in
coastal
deserts
(Rundel,
unpublished
data).
PHYSIOLOGICAL
ADAPTATIONS
Field studies
of
photosynthesis
and
water
relations of desert lichens
subject
to
high
humidities or
fog
condensation are limited
to
experiments
in
Israel.
Measure-
ments
of
CO2
exchange
of lichens
in
natural habitats
in
the
Negev
Desert
have dem-
onstrated that Niebla
maciformis
(=
Ramalina
maciformis),
Teloschistes
lacunosus
and six
species
of
Caloplaca,
Diploschistes,
Xanthoria and
Squamaria
are able
to
photosynthesize using
only
water from dew condensation
or water
vapor uptake
(Lange,
1969;
Lange
et
al., 1970a,b,
1975).
Similar
adaptations
to water
vapor
uptake
have
also been shown for
several Antarctic lichens
(Gannutz,
1970;
Lange
&
Kappen,
1972).
For Niebla
maciformis, average
dew condensation
is sufficient for
approximately
three hours of
positive
net
photosynthesis
following
sunrise
(Lange
et
al.,
1970a).
With a
frequency
of dew condensation of 198
nights
per year,
the
annual
increase
in
lichen
biomass is
5-10%
(Lange
et
al.,
1975).
Similar calculations have
been
made
for Cal-
oplaca
aurantia
in
the same habitat
(Lange
&
Evenari,
1971).
Although
field
physiological
data
is not
available
for
lichens
in
true
coastal
fog
deserts,
a
considerable amount
of
data has
been
compiled
on
laboratory experiments
with
a
group
of
Baja
California
species
(Rundel
&
Lange,
unpublished
data).
These
studies reveal both similarities and differences
from
patterns
observed
in
the
Negev
Desert.
Unlike
other desert
lichens,
desert
fog
zone taxa
frequently
experience
thallus
moisture
saturation
lasting
for
several
days.
While
Niebla
maciformis,
rarely
saturated
in
the
Negev,
exhibits no
decline
in
rate of
photosynthetic
assimilation
with
increasing
moisture
content
(Lange
et
al.,
1975),
a
pattern
of
rapid drop
in
assimilation
rate
is
characteristic
of
typical fog
zone taxa. Niebla
maciformis
has
no
decline
in
assimilation
at 10
or 20?C
while
the
sand form of Niebla homalea has
a
sharp
decline at both
temperatures.
The
saxicolous
form
of
N.
homalea,
zoned
higher
and further
from the
ocean
along
the
coast
of
Baja
California,
has no
decline
in assimilation at
10?
but
a
sharp
decline
at 20?C. The observed
gradient
in
water relations
response
is
contrary
to what
might
be
expected
since the
greatest pattern
of
decline
in
assimilation
with
approaching
saturation
is
associated
with the
greatest
frequency
of
saturation
condi-
tions from
fogs.
The
gradient
can be
explained hypothetically,
however,
by
patterns
[Volume
81
288
THE
BRYOLOGIST
RUNDEL:
DESERT
FOG ZONE
LICHENS
0.3-
DENDROGRAPHA
LEUCOPHAEA
0.1-
(mg
C02
9gd-wt
h
-I)
-0.1-
45000 lux
-0.3-
dark
5
10
15 2io
25
30
Temperature
(C)
FIGURE 4.
Photosynthetic response
to
temperature
and
light intensity
in
saturated
thalli of
Dendrographa
leucophaea
Tuck. Darb.
Points are mean
values
for
four
thalli.
of cortical
thickness.
Thick
cortices,
an
important adaptation
in
lichens
subject
to
frequent high
winds
(Ahmadjian,
1970;
Rundel, unpublished
data),
swell
tightly
when
saturated
with
moisture,
restricting
gas
exchange
to
the
algal
layer.
Cortices are
thick-
est
in
the
exposed
sand
populations
of Niebla
homalea,
intermediate
in
the less
ex-
posed
rock
form
of this
species
and
relatively
thin
in
N.
maciformis.
Patterns
of
photosynthetic
response
at
thallus
saturation are
shown for Dendro-
grapha
leucophaea
in
Figure
4. At
light
intensities above 9000
lux
(350
,uE m-2
s-1)
maximal
CO2
assimilation
occurs at
a
relatively
cool
10?C.
This
maximal
rate
is
ap-
proximately
30% of the maximal
value at
optimal
thallus
water content.
Other
fog
desert lichens
in
Baja
California have
saturation values
30-50%
of
optimal
water con-
tent levels
(Rundel
&
Lange,
unpublished
data;
Nash et
al., 1977).
Above
23?C,
no
net
positive
CO2
assimilation
occurs.
Physiological
tolerances
to
high
salinities
are
important
adaptations
in
coastal
li-
chens
subject
to
salt
spray
or
windborne aerosol
salts.
Follmann
(1967a)
described
heavy
salt
encrustations
on coastal
lichens
in
central
Chile
and
speculated
that
hydro-
philic
salt
crusts
may
improve
the water
relations of these
lichens
by forming
a
fa-
vorable
water
potential gradient
for
uptake
of moisture.
Although
published
data
by
Follmann
(1967a;
1967b)
are difficult
to
interpret
because
of unrealistic
time
axes,
the
phenomenon
he describes
appears
to
be
true.
1978]
289
THE
BRYOLOGIST
Dendrographo
leucophoea
-
salt
crust
60
Niebla
homalea
-
salt crust
Thallus
Moisture
C/Moisture
//
Dendrographa leucophaea
Content
(%
dry
wt.)
..r'
~~~~/
/
^Niebla
homolea
40-
20
10
2
6
10
14
18
22
26
30
34
38
42
Time
(hours)
FIGURE
5. Water
uptake by
salt-encrusted and
non-encrusted thalli of
Dendrographa
leu-
cophaea
Tuck.
Darb. and
Niebla
homatea Ach. Rund. &
Bowl. Points
are
mean value
for four
thalli.
Comparative
data for
moisture
uptake
of air
dry
thalli
previously
saturated
with
salt
water
and with deionized water
are shown
in
Figure
5
for two
species
of lichens
from
Baja
California.
In
Niebla
homalea
(sand
form)
saturation
at
100%
relative
hu-
midity
is reached at a
water content
of
40% of
dry
weight
in
thalli without a salt crust.
[Volume
81
290
RUNDEL:
DESERT
FOG ZONE
LICHENS
When a crust is
present,
saturation moisture content is
nearly
60%.
In
Dendrographa
leucophaea
salt crusts increase the
saturation moisture
content from 45% to 75%.
Experiments
investigating
the
physiological
tolerance of lichens to
high
osmotic
potential
have shown that coastal lichens
are
favorably adapted
to
maintaining high
rates
of
photosynthesis
under
considerable
osmotic stress
(Rundel
&
Lange,
unpub-
lished
data).
The maximal
photosynthetic
rate of
Dendrographa
leucophaea
over
a
drying
curve
at 20?C
and
45,000
lux
(1900
,uE
m-2
s-1)
is
unaffected
by
saturation
in
sea
water or
2
M
NaCl
(-98
bars)
even
with
original
saturation of
4 M
NaCl
(-252
bars),
photosynthesis
rates are
30%
of
maximal values of thalli
treated with deionized
water. Reduced levels of
maximal
photosynthesis
rates occur
in
drying
curves
for sea
water saturated
thalli of
Niebla homalea and
N.
josecuervoi
and amount
to 50-90%
of
normal values.
Although
the
physiological
tolerance of coastal zone
lichens
is
highly
adapted,
lichens
in
general appear
to have a
genetic pre-adaptation
of
osmotic stress
tolerance. Even Ramalina
fraxinea
and Lobaria
pulmonaria,
characteristic
of
envi-
ronments free
of
salt
encrustations,
have
positive
rates
of
photosynthetic
assimilation
at
osmotic
potentials
in
excess of -370 bars
(Rundel
&
Lange,
unpublished
data).
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V.
1970.
Adaptations
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2.
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1973.
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[Volume
81
292
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