Does breeding system contribute to the rarity of Hydrastis canadensis?


Sanders, S.M.; Mcgraw, J.B.

Ecological Society of America Annual Meeting Abstracts 88: 295-296

2003


lated
factors.
Differences
in
vegetation
structure
and
productivity
on
tree
islands
in
relation
to
hydrology
may
help
in
establishing
monitoring
criteria
for
the
assessment
of
Everglades
restoration
efforts.
SALKELD,
DAN.*
James
Cook
University,
Townsville,
Australia.
Para-
site
regulation
of
a
lizard
population.
Parasites
can
regulate
host
populations
by
reducing
host
survival
and
fe-
cundity.
I
illustrate
the
impact
of
naturally
occurring
haemogregarines
(par-
asitic
protists)
upon
life
history
of
the
eastern
water
skink
(Eulamprus
quoyii),
an
Australian
viviparous
lizard.
Using
mark-recapture
data,
and
the
Anderson-Gordon
model
(1982),1
show
that
haemogregarines
do
not
affect
survival
of
their
skink
hosts.
However,
fecundity
is
reduced
by
parasitic
infection
as
heavily
infected
skinks
produce
smaller
litters
than
skinks
with
small
parasite
loads.
Poulin
&
Vickery
(1996).
suggest
that
parasites
can
also
reduce
fecundity
by
affecting
female
mate
choice.
The
impact
of
pro-
tist
infection
upon
lizard
mating
strategy
(the
extent
of
polygyny)
is
ex-
amined
using
evidence
from
microsatellite
markers.
SALO,
LUCINDA
E*
USGS
Snake
River
Field
Station,
Boise,
ID.
Intro-
duced
(Prosopis
julifiora
and
Azadirachta
indica)
and
native
(Acacia
nilotica
var.
adansonia)
trees
spreading
in
Senegal,
West
Africa.
Plant
invasions
from
the
Old
World
to
the
New
World
are
more
frequent
than
the
reverse.
Many
of
the
New
World
plants
that
have
become
invasive
in
the
Old
World
are
woody
species
and
many
of
these
were
intentionally
introduced.
Determining
the
age
structure
of
a
population
is
a
first
step
in
understanding
whether
or
not
it
is
regenerating
and
in
predicting
whether
or
not
it
may
spread
and
become
invasive.
This
study
determined
the
size
structure,
and
mapped
all
individuals,
of
three
woody
species
at
a
site
at
Foundiougne,
Fatick
Region,
Senegal.
These
included
mesquite
(Prosopis
juliflora),
introduced
from
Central
America,
and
neem
(Azadirachta
indica),
introduced
from
India.
I
also
examined
the
only
native
tree
regen-
erating
at
this
site,
Acacia
nilotica
var.
adansonia.
These
three
species
were
all
represented
by
large
numbers
of
seedlings
and
progressively
fewer
in-
dividuals
of
successively
larger
size
classes.
This
indicates
that
these
spe-
cies
are
regenerating
successfully
and
that
introduced
species
are
spreading
from
where
they
were
planted.
All
other
native
tree
species
at
this
site
were
represented
only
by
a
few
mature,
heavily
used
individuals.
The
Prosopis
and
the
Acacia
species
both
appear
able
to
regenerate,
and
to
spread,
due
to
1)
spines
that
reduce
browsing
and
rooting
by
livestock,
2)
the
ability
to
resprout
after
browsing,
2)
pods
that
are
eaten
and
spread
by
livestock,
and
3)
low
frequency
of
fire,
due
to
heavy
grazing
by
livestock.
SALTONSTALL,
KRISTIN.*
University
of
Maryland
Center
for
Environ-
mental
Science,
Horn
Point
Laboratory,
Cambridge,
MD,
USA.
A
histor-
ical
perspective
on
a
cryptic
invasion:
Phragmites
australis.
Over
the
past
century,
one
of
the
most
conspicuous
changes
to
marshes
along
the
Atlantic
coast
is
the
rapid
spread
of
Phragmites
australis.
While
native
to
these
communities
over
much
of
this
range,
evidence
suggests
that
the
widespread
invasions
of
this
species
are
due
to
the
introduction
of
a
EurAsian
lineage
of
Phragmites
which
has
both
outcompeted
native
pop-
ulations
of
the
species
as
well
as
moved
into
sites
where
it
was
not
found
historically.
Native
populations
persist
in
some
sites
but
little
is
known
about
their
ecology
and
whether
or
not
they
will
be
able
to
compete
with
introduced populations.
Clear
determinations
of
human
influences
on
this
invasion
are
elusive,
however
it
is
apparent
that
substrate
disturbance,
al-
terations
in
hydrology,
and
nutrient
inputs
facilitate
establishment
and
spread
of
the
introduced
lineage.
Today
introduced
Phragmites
is
the
dom-
inant
macrophyte
in
many
intertidal
environments
and
is
considered
poor
habitat
by
many
due
to its
high
standing
biomass
and
ability
to
rapidly
accrete
sediments
thus
altering
marsh
hydrology.
Such
characteristics
may
prove
valuable
however
in
the
face
of
sea
level
rise
and
recurrent
nutrient
inputs
due
to
coastal
development.
SAMUELS,
IVAN
A.*
University
of
Florida,
Gainesville,
Florida,
USA.
Invasion
of
Chinese
Tallow
(Sapium
sebiferum):
Dispersal
and
recruit-
ment
limitation
in
multiple
habitats.
Studies
of
exotic
plant
invasions
have
often
focused
on
spread
and
impact
of
these
species,
as
well
as
the
processes
that
facilitate
invasion.
However,
little
attempt
has
been
made
to
understand
why
particularly
invasive
plants
do
not
establish
in
potentially
suitable
habitats where
dispersal
of
their
seeds
may
be
high.
1
compared
both
dispersal
and
post-dispersal
processes
of
Sapium
sebiferum
(Chinese
Tallow)
in
four
habitats,
two
wet
prairie
habitats where
the
plant
is
currently
invading,
and
two
adjacent
forest
hab-
itats
where
it
is
absent,
but
where
it
occurs
elsewhere
in
its
non-native
range.
I
observed
foraging
birds
to
quantify
the
number
of
seeds
removed
and
post-foraging
movements,
and
used
point
counts
to
estimate
the
density
of
seed
dispersing
bird
species
in
the
non-invaded
habitats.
In
addition,
1
experimentally
placed
seeds
in
each
of
the
four
habitats
to
compare
seed
predation,
germination,
and
seedling
survivorship
rates.
Of
30
species
of
birds
that
visited trees,
53%
ingested
seeds
and
20%
carried
seeds
away
from
parent
trees.
After
foraging,
these
species
frequently
moved
into
forest
habitats,
where
they
were
commonly
detected
on
point
counts.
Thus,
dis-
persal
limitation
is
unlikely
to
explain
the
absence
of
S.
sebiferum
in
the
two
forest
habitats.
Differences
in
seed
predation
are
likewise
unable
to
explain
recruitment
limitation
in
forest
sites,
as
it
was
significantly
lower
than
in
wet
prairie.
On-going
germination
tests
and
monitoring
of
seedlings
will
identify
the
stage/s
that
act
as
a
barrier
to
establishment
in
forest
habitats,
and
the
relative
importance
of
these
stages
on
the
overall
proba-
bility
of
recruitment.
SANDERS,
NATHAN
J.*
Department
of
Biological
Sciences,
Humboldt
State
University,
Arcata,
CA.
Do
we
need
to
worry
even
more
about
invasive
ants?
It
is
abundantly
clear
that
invasive
species
and
global
climate
change
threat-
en
the
integrity
of
many
native
communities
and
ecosystems.
Recent
re-
views
and
research
suggest
climate
change
and
the
spread
of
invasive
spe-
cies
may
act
in
concert
and
that
global
change
may
exacerbate
the
spread
of
invasive
species.
In
this
talk,
1
examine
(i)
the
relationship
among
cli-
mate
and
ant
species
richness,
(ii)
how
predicted
climate
change
may
affect
both
species
richness
and
the
success
of
many
invasive
species,
and
(iii)
how
predicted
climate
change
will
aid
the
spread
of
two
of
the
most
con-
spicuous
invasive
ant
species
in
the
US,
Solenopsis
invicta
in
the
southern
US
and
Linepithema
humile
in
the
western
US.
Climatic
variation
is
ob-
viously
related
to
variation
in
ant
species
richness,
but
the
relationship
changes
with
scale.
Likewise,
the
effects
of
predicted
climate
change
on
ant
species
richness
also
vary
with
scale.
The
distributions
of
most
invasive
species
will
be
affected
by
changing
climate,
but
probably
not
in
systematic
ways.
Finally,
preliminary
analyses
suggest
predicted
climate
change
will
enhance
the
spread,
and
likely
the
impact,
of
both
S.
invicta
and
L.
humile
on
native
communities.
So,
at
least
for
these
two
species,
we
should
worry
even
more.
SANDERS,
SUZANNE
M.*
and
JAMES
B.
MCGRAW.
West
Virginia
University,
Morgantown,
WV,
USA.
Does
breeding
system
contribute
to
the
rarity
of
Hydrastis
canadensis?
Abundance
of
Hydrastis
canadensis
(goldenseal)
in
the
eastern
deciduous
forest
is
declining.
This
decline
may
be
directly
or
indirectly
linked
to
the
breeding
system
of
this
species.
For
example,
this
species
reproduces
pri-
marily
clonally,
forming
dense
patches.
These
patches
are
often
separated
by
great
distances,
such
that
obligate
outcrossing
could
limit
seed
produc-
tion
and/or
viability.
To
test
for
breeding
system
type,
we
implemented
treatments
on
ramets
from
three
natural
source
populations.
To
avoid
dif-
ficulties
associated
with
field
pollination,
this
study
was
conducted
in
a
greenhouse.
The
location
of
flowering
ramets
were
marked
at
all
three
source
populations
in
2001.
These
were
removed
in
March
2002
prior
to
emergence
and
planted
in
a
standard
potting
mix.
Six
treatments
were
im-
plemented.
Our
results
showed
that
1)
this
species
is
not
apomictic,
2)
seed
set
occurred
via
self
pollination,
both
with
and
without
assistance,
3)
seed
set
occurred
via
outcrossing
with
ramets
from
the
same
source
population
and
with
ramets
from
other
source
populations
and,
4)
seed
set
of
field
controls
at
the
source
populations
was
greater
than
that
of
the
greenhouse
treatments.
Tetrazolium
testing
showed
that
all
seeds
were
viable.
These
results
suggest
that
breeding
system
type,
and
seed
production,
are
not
factors
limiting
the
abundance
and
spread
of
H.
canadensis.
However,
seed-
lings
are
only
uncommonly
observed
in
natural
populations.
Seedlings
can
be
readily
distinguished
from
small
vegetative
ramets
because
only
coty-
ledons
are
produced
during
the
first
year
of
growth.
This
suggests
seed
Abstracts
295
germination
may
be
a
factor
limiting
abundance
and
spread
of
this
species.
Changes
in
disturbance
regimes
and/or
faunal
composition
of
the
eastern
deciduous
forest
may
limit
seed
germination.
SANFORD,
ROBERT
L.,'•*
JAYNE
BELNAP,
2
SARAH
GOPALANI.'
NATHAN
J.
WOJCIK'
and
MAXWELL
J.
RICHARDSON."
University
of
Denver,
Denver,
CO;
=
USGS
-
Biological
Resources,
Moab,
UT.
Cheat-
grass
(Bromus
tectorum
L.)
and
seasonal
patterns
of
soil
phosphorus
availability
in
arid
ecosystems.
Seasonal
changes
in
soil
phosphorus
(P)
availability
are
not
yet
known
for
many
ecosystems.
We
report
seasonal
changes
in
several
pools
of
soil
phos-
phorus.
including
plant
available
P
from
the
Mojave
Desert
and
Colorado
Plateau.
In
addition
we
show
that
cheatgrass
changes
soil
P
fractions
in
unexpected
and
ecologically
significant
ways.
Monthly
soil
samples
(0-10
cm)
from
four
sites
in
Canyonlands
National
Park
in
southeast
Utah,
are
analyzed
for
P
with
a
modified
Hedley
P
fractionation
method.
Labile
P
(plant
available)
peaks
in
spring
and
autumn
with
significant
monthly
var-
iation.
Surprisingly,
HCI
extractable
P
changes
as
well,
with
a
pattern
in-
verse
to
that
of
labile
P.
Each
of
these
sites
has
considerable
Bromus
tee-
tortim
L.
(cheatgrass)
invasion.
In
a
separate
greenhouse
study
with
four
contrasting
soils (0-10
cm)
from
the
Mojave
desert
CA
and
NV,
we
grew
cheatgrass
for
100
days
to
test
for
soil
P
changes.
Regardless
of
the
soil
type,
cheatgrass
causes
large
(2x)
increases
in
labile
P
and
large
(90%)
decreases
in
both
NaOH
and
HCl
extractable
P.
In
addition,
root
biomass,
root
nitrogen
(N)
and
P
as
well
as
shoot
biomass
and
shoot
N
and
P
vary
widely
according
to
soil
type.
We
propose
that
cheatgrass
roots
solubilize
large
amounts
of
soil
phosphorus
seasonally,
from
P
pools
that
are
consid-
ered
unavailable
to
most
plant
species,
and
that
this
solubilized
P
becomes
available
for
Broumus
tectorum
L.
uptake.
These
results
are
discussed
in
the
contexts
of
root
exudates,
mycorrhizae
and
root
rhizosphere
effects
on
desert
soil
P.
SANKARAN,
MAHESH'
=
and
DAVID
AUGUSTINE."
NERC
Centre
for
Population
Biology.
Imperial
College
at
Silwood
Park,
Ascot.
Berkshire.
UK;
=
NREL,
Colorado
State
University,
Fort
Collins,
CO,
USA;
Syracuse
University,
Syracuse,
NY.
USA.
Consumer-decomposer
interactions
in
a
semi-arid
grazing
ecosystem.
Ecosystem-level
studies
of
producer-decomposer
interactions
have
focused
primarily
on
plant
production
and
soil
texture
as
regulators
of
decomposer
abundance,
but
have
rarely
considered
the
role
of
grazers
in
mediating
such
interactions.
Here,
we
conducted
replicated
exclosure
experiments
at
both
high
and
low
levels
of
soil
fertility
to
investigate
the
effects
of
large.
mam-
malian
grazers
on
decomposer
biomass
and
activity
patterns
in
a
semi-arid
grazing
ecosystem
in
Kenya.
Within
only
2
years
of
grazer
exclusion,
mi-
crobial
biomass
increased
in
fenced
grassland
across
all
levels
of
soil
fer-
tility,
indicating
that
grazers
regulate
decomposer
populations
in
this
system
by
depressing
the
quantity
and/or
quality
of
plant
inputs
to
soils.
However,
across
all
study
sites,
microbial
biomass
was
highly
correlated
with
soil
carbon
content,
suggesting
that
landscape-scale
constraints
on
soil
organic
matter
content
are
even
more
important
than
grazing
in
regulating
microbial
abundance.
As
soil
organic
carbon
levels
increased,
both
microbial
biomass
and
the
fraction
of
soil
carbon
accounted
for
by
microbes
increased,
and
this
was
associated
with
an
increased
efficiency
of
resource
utilization
by
microbes
and
lowered
carbon
turnover
rates
in
soils.
Our
results
support
previous
ecosystem-level
studies
showing
that
microbial
biomass
and
growth
are
constrained
by
plant
production
and
soil
C
availability.
In
ad-
dition,
our
findings
also
demonstrate
that
decomposer
abundance
can
be
influenced
by
an
ecosystem's
trophic
structure,
with
significant
reductions
in
biomass
occurring
as
a
result
of
herbivores
diverting
plant
carbon
away
from
soils.
SANTIAGO,
LOUIS
S.
University
of
Florida,
Department
of
Botany,
PO
Box
118526,
Gainesville,
FL,
USA.
Linking
plant
physiological
ecology
to
ecosystem
science:
Effects
of
life
history
traits
on
leaf
decomposition.
Plant
life
history
traits
such
as
wood
density,
photosynthesis
and
anti-her-
bivore
defenses,
were
compared
with
leaf
litter
decomposition
rates
(2
years)
on
a
broad
selection
of
plant
growth
forms
including
palms,
lianas,
canopy
trees
and
pioneer
trees
in
Panamanian
lowland
wet
forest.
Leaf
nitrogen
had
a
strong
positive
effect
on
leaf
decomposition
rate,
whereas
anti-herbivore
defenses
had
a
strong
negative
effect
on
decomposition.
Leaf
nitrogen
also
had
a
strong
positive
effect
on
leaf
photosynthetic
rate
and
anti-herbivore
defenses
were
negatively
correlated
with
photosynthesis.
Wood
density
appeared
to
constrain
suites
of
traits.
Species
with
low
wood
density
exhibited
high
photosynthetic
and
decomposition
rates.
In
contrast.
species
with
low
wood
density
exhibited
leaves
with
lower
photosynthetic
rates
that
were
relatively
slow
to
decompose.
In
general,
wood
density
is
negatively
correlated
with
plant
growth
rate
and
therefore
reflects
variation
along
an
axis
of
life
history
traits.
The
observation
that
leaf
photosynthesis
and
decomposition
are
driven
by
the
same
interdependent
suite
of
char-
acteristics
suggests
that
the
axis
of
plant
life
history
traits
can
be
extended
to
decomposition.
Therefore,
the
effects
of
plant
species
on
decomposition
at
the
ecosystem
scale
can
be
understood
in
terms
of
specific
allocation
patterns
that
reflect
plant
strategies.
SARNELLE,
ORLANDO.*
Department
of
Fisheries
and
Wildlife,
Michi-
gan
State
University,
East
Lansing.
Ml,
USA.
Keystone-predation
revis-
ited:
Herbivore
effects
on
phytoplankton
diversity
and
grazing-resis-
tance.
Keystone
predation
models
predict
that
a
selective
predator
can
promote
coexistence
among
competing
prey,
and
so
enhance
prey
diversity,
when
the
predator
selectively
kills
the
competitively-superior
prey.
This
implies
that
there
is
a
tradeoff
between
resistance
to
predation
and
competitive
ability
at
low
resource
levels
among
prey
species.
In
this
case,
keystone
predators
promote
both
prey
diversity
and
dominance by
more
resistant
prey.
It
is
also
possible
for
a
selective
predator
to
promote
dominance
by
prey
species
that
are
less
resistant
to
predation,
if
there
is
a
tradeoff
between
resistance
to
predation
and
competitive
ability
at
high
resource
levels
among
prey
species.
However
in
this
case,
keystone
predation
theory
pre-
dicts
that
the
predator
is
not
likely
to
promote
prey
diversity.
I
present
experimental
evidence
demonstrating
that
Daphnia,
a
selective
grazer,
can
act
as
a
keystone
predator
(i.
e.,
promote
phytoplankton
diversity)
without
shifting
the
phytoplankton
community
to
dominance
by
more
resistant
spe-
cies.
There
appear
to
be
multiple
strategies
for
dealing
with
high
predation
pressure
among
the
phytoplankton.
such
that
a
selective
predator
can
in-
crease
prey
diversity
by
simultaneously
promoting
dominance
by
species
that
are
resistant
to
predation
and
species
with
high
maximum
growth
rates
that
are
vulnerable
to
predation.
SAUER,
SUZANNE
L.
and
ROGER
C.
ANDERSON.*
Illinois
State
Uni-
versity,
Normal,
Illinois,
United
States.
Modifying
distance
methods
to
estimate
historical
tree
density
from
General
Land
Survey
Records.
Various
researchers
have
used
the
Government
Land
Office
(GLO)
survey
records
to
determine
historic
vegetation
through
the
application
of
the
dis-
tance
methods
to
witness
tree
data.
We
test
the
suitability
of
applying
mod-
ifications
of
the
random
pairs
method
or
the
quarter
method
to
GLO
records
from
the
Shawnee
National
Forest
Purchase
Area
in
southern
Illinois.
The
witness
tree
data
was
evaluated
with
criteria
based on
the
distribution
of
the
witness
trees
around
the
section
or
quarter
section
points.
As
a
whole,
the
data
set
did
not
meet
all
criteria
for
either
method.
Data
were
subdivided
into
groups
meeting
specific
criteria.
For
interior
points
with
two
witness
trees,
the
random
pair
method
with
an
exclusion
angle
of
202.93
degrees
provided
the
best
modification
of
the
distance
methods
to
convert
witness
tree
distances
to
tree
density.
A
derived
correction
factor
of
0.74
to
convert
the
mean
witness
tree
distance
to
the
square
of
the
mean
area
was
deter-
mined
by
regressing
exclusion
angle
against
correction
factor.
Wilcoxon
sign-rank
tests
indicate
that
there
are
significant
differences
in
the
calcu-
lated
square
root
of
the
mean
based
on
distance
method
used
(quarter
meth-
od
v.
random
pairs
S=3665417,
p<0.001:
random
pairs
vs.
the
derived
0.74
correction
factor
S=3893716.
p<0.001).
SAUNDERS,
COLIN
J.,'•*
JAMES
F.
REYNOLDS,'
J
P.
MEGONIGAL'
and
BERT
G.
DRAKE.=
'
Department
of
Biology,
Duke
University,
Dur-
ham,
NC,
USA;
=
Smithsonian
Environmental
Research
Center,
Edgewater,
MD,
USA.
Modeling
the
past
500
years
of
organic
matter
accumulation
in
a
Chesapeake
Bay
salt
marsh.
Evidence
from
salt
marshes
along
the
Atlantic
Coast
indicates
the
com-
position
of
plant
species
has
changed
in
the last
century,
attributed
to
296
Abstracts