I'm entertained. Bore me.

[BelleCarolinaPeridot]

Not really I am bored as hell. I had a looooooooong week and all the energy was drained out of me.

[Generic Brad]

1. Here's a twisted nursery rhyme

Little Jack Horner
Sat in a corner
Scratching his eye with his thumb
When he pulled it out
He began to shout
"What have I done to my eye?
I'm blind!"

Are you amused yet?

[Kutjara]

4. Mary had a little lamb:

Mary had a little lamb,
And it was always gruntin'.
She took it out behind the barn,
And kicked it's f**king c**t in.

[otherlander]

5. Mary had a little lamb

you've heard this song before.
But did you know she passed her plate
and had a little more?

[Kutjara]

2. Here ya go:

Titre du document / Document title
Adiabatic vacuum states on general spacetime manifolds: Definition, construction, and physical properties

Auteur(s) / Author(s)
JUNKER W. (1) ; SCHROHE E. (2) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)
(1) Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, Am Mühlenberg 1, 14476 Golm, ALLEMAGNE
(2) Universität Potsdam, Institut für Mathematik, Am Neuen Palais 10, 14415 Potsdam, ALLEMAGNE

Résumé / Abstract
Adiabatic vacuum states are a well-known class of physical states for linear quantum fields on Robertson-Walker spacetimes. We extend the definition of adiabatic vacua to general spacetime manifolds by using the notion of the Sobolev wavefront set. This definition is also applicable to interacting field theories. Hadamard states form a special subclass of the adiabatic vacua. We analyze physical properties of adiabatic vacuum representations of the Klein-Cordon field on globally hyperbolic spacetime manifolds (factoriality, quasiequivalence, local definiteness, Haag duality) and construct them explicitly, if the manifold has a compact Cauchy surface.

Revue / Journal Title
Annales Henri Poincaré (Ann. Henri Poincaré) ISSN 1424-0637


Source / Source
2002, vol. 3, no6, pp. 1113-1181 <69 page(s) (article)> (51 ref.)

Langue / Language
Anglais

Editeur / Publisher
Birkhäuser, Basel, SUISSE (2000) (Revue)

Mots-clés anglais / English Keywords
Symplectic bilinear form ; Hyperbolic space ; Fundamental solution ; Paracompact manifold ; Uniqueness theorem ; Existence theorem ; Quantum field theory ; Symplectic manifold ; Bilinear form ; Linear operator ; Sobolev space ; Space-time ; Scalar fields ; Mathematical manifolds ; Cauchy problem ; Klein-Gordon equation ;
Mots-clés français / French Keywords
Form bilinéaire symplectique ; Espace hyperbolique ; Solution fondamentale ; Variété paracompacte ; Théorème unicité ; Théorème existence ; Théorie quantique champ ; Variété symplectique ; Forme bilinéaire ; Opérateur linéaire ; Espace Sobolev ; Espace temps ; Champ scalaire ; Variété mathématique ; Problème Cauchy ; Equation Klein Gordon ;

001b00c65d ; 001a02e08 ;
Mots-clés espagnols / Spanish Keywords
Teorema unicidad ; Teorema existencia ; Variedad simpléctica ; Forma bilineal ; Operador lineal ; Espacio Sobolev ;
Localisation / Location
INIST-CNRS, Cote INIST : 26965, 35400010366103.0020



----------------------------

enjoy!!!

[Arugula Latte]

3. Think about Joe Lieberman speaking ...

Droopy Dawg's voice is droning on. The hole in his strangely slack face is opening and closing as he forms meaningless sentences. Blah blah de frickin' blah ...

[Dangerously Amused]

13. Yeah. Like this:

[Floogeldy]

6. I have just the thing for you, CarolinaPeridot

Invasive Plant Suppresses the Growth
of Native Tree Seedlings by Disrupting
Belowground Mutualisms
Kristina A. Stinson1, Stuart A. Campbell2, Jeff R. Powell2, Benjamin E. Wolfe2, Ragan M. Callaway3, Giles C. Thelen3,
Steven G. Hallett4, Daniel Prati5, John N. Klironomos2*
1 Harvard Forest, Harvard University, Petersham, Massachusetts, United States of America, 2 Department of Integrative Biology, University of Guelph, Guelph, Ontario,
Canada, 3 Division of Biological Sciences, University of Montana, Missoula, Montana, United States of America, 4 Department of Botany and Plant Pathology, Purdue
University, West Lafayette, Indiana, United States of America, 5 Department of Community Ecology, UFZ Centre for Environmental Research, Halle, Germany
The impact of exotic species on native organisms is widely acknowledged, but poorly understood. Very few studies
have empirically investigated how invading plants may alter delicate ecological interactions among resident species in
the invaded range. We present novel evidence that antifungal phytochemistry of the invasive plant, Alliaria petiolata, a
European invader of North American forests, suppresses native plant growth by disrupting mutualistic associations
between native canopy tree seedlings and belowground arbuscular mycorrhizal fungi. Our results elucidate an indirect
mechanism by which invasive plants can impact native flora, and may help explain how this plant successfully invades
relatively undisturbed forest habitat.
Citation: Stinson KA, Campbell SA, Powell JR, Wolfe BE, Callaway RM, et al. (2006) Invasive plant suppresses the growth of native tree seedlings by disrupting belowground
mutualisms. PLoS Biol 4(5): e140. DOI: 10.1371/journal.pbio.0040140
Introduction
Widespread anthropogenic dispersal of exotic organisms
has raised growing concern over their devastating ecological
impacts, and has prompted decades of research on the
ecology of invasive species <1–3>. Exotic plants may become
aggressive invaders outside their home ranges for a number
of reasons, including release from native, specialized antagonists
<4>, higher relative performance in a new site <5>, direct
chemical (allelopathic) interference with native plant performance
<6>, and variability in the responses and resistance
of native systems to invasion <7,8>. Thus, successful invasion in
many cases appears to involve the fact that invasive species
are not at equilibrium, and are either freed of long-standing
biotic interactions with their enemies in the home range, and/
or disrupt interactions among the suite of native organisms
they encounter in a new range <9>. Nevertheless, experimental
data on species-level impacts of exotic plants are still limited
<10>. One particularly understudied area is the potential for
invasive plants to disrupt existing ecological associations
within native communities <6,10>. Many exotic and native
plants alike depend upon mutualisms with native insects,
birds, or mammals for pollination and seed dispersal <11>, and
with soil microbes for symbiotic nutrient exchange <12>. Thus,
when an introduced species encounters a new suite of
resident organisms, it is likely to alter closely interlinked
ecological relationships, many of which have co-evolved
within native systems <6,11>.
One such relationship is that between plants and mycorrhizal
fungi <12>. Most vascular plants form mycorrhizal
associations with arbuscular mycorrhizal fungi (AMF) <12>,
and many plants are highly dependent on this association for
their growth and survival <12>, particularly woody perennials
and others found in late-successional communities <13>. In
contrast, many weedy plants, in particular non-mycotrophic
plants, can be negatively affected by AMF <14–16>. Naturalized
exotic plants have been found to be poorer hosts and
depend less on native AMF than native plants <17>. They often
colonize areas that have been disturbed <2>, and disturbances
to soil have been shown to negatively impact AMF functioning
<18>. Furthermore, it has been proposed that the
proliferation of plants with low mycorrhizal dependency
may degrade AMF densities in the soil <17>. However, a few
invasive plants proliferate in the understory of mature
temperate forests <2>, where AMF density is typically high
<19>. The existing mycelial network in mature forest soils may
facilitate the establishment of exotic, mycorrhizal-dependent,
recruits <20,21>, but this should not be the case for nonmycorrhizal
invaders. If non-mycorrhizal invasive plants
establish and degrade AMF in mature forests, then the effects
on certain resident native plants could be substantial.
One of the most problematic invaders of mesic temperate
forests in North America is Alliaria petiolata (garlic mustard;
Brassicaceae), a non-mycorrhizal, shade-tolerant, Eurasian
biennial herb which, like most other mustards, primarily
occupies disturbed areas. Garlic mustard is abundant in
forest edges, semishaded floodplains, and other disturbed
sites in its home range <22>. However, this species has recently
become an aggressive and widespread invader of both
Academic Editor: Michel Loreau, McGill University, Canada
Received December 5, 2005; Accepted March 1, 2006; Published April 25, 2006
DOI: 10.1371/journal.pbio.0040140
Copyright:
2006 Stinson et al. This is an open-access article distributed under
the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author
and source are credited.
Abbreviations: AMF, arbuscular mycorrhizal fungi; ANOVA, analysis of variance;
REGW, Ryan-Einot-Gabriel-Welsch
* To whom correspondence should be addressed. E-mail: [e-mail]
PLoS Biology | www.plosbiology.org May 2006 | Volume 4 | Issue 5 | e140 0727
PLoS BIOLOGY
disturbed areas and closed-canopy forest understory across
much of the United States and Canada <23>, where it
apparently suppresses native understory plants, including
the seedlings of dominant canopy trees <22,24>. The mechanism
underlying garlic mustard’s unusual capacity to enter
and proliferate within intact North American forest community
has not yet been established.
As shown in recent greenhouse experiments, garlic
mustard’s impact on native understory flora may involve
competitive <25> or allelopathic effects on native plants <26>,
but it has also been hypothesized that this species interferes
with plant–AMF interactions in its invaded range <27>.
Members of the Brassicaceae, including garlic mustard,
produce various combinations of glucosinolate products
<28>, organic plant chemicals with known anti-herbivore,
anti-pathogenic and allelopathic <29> properties, that may
also prevent this non-mycorrhizal plant family from associating
with AMF <30>. These phytochemicals may be released
into soils as root exudates, as a result of damaged root tissue,
or in the form of leaf litter. High densities of garlic mustard
in the field correlate with low inoculum potential of AMF,
and extracts of garlic mustard leaves have been shown to
reduce the germination of AMF spores and impair AMF
colonization of cultivated tomato roots in laboratory settings
<27>. Although not all Brassicaceae are invasive, it is possible
that garlic mustard’s successful invasion of understory
habitats involves the negative effects of its phytochemistry
on the native plant and AMF species it encounters outside its
home range. Others have shown that exotic plants can recruit
different suites of microbial organisms in their new ranges
that can be antagonistic to native plants <6>. However, to our
knowledge, no previous studies have directly tested whether
this species or any other exotic plant disrupts native plant–
AMF mutualisms within natural communities. Here, we
present novel evidence that garlic mustard negatively impacts
the growth of AMF-dependent forest tree seedlings by its
disruption of native mycorrhizal mutualisms. We further
show that, because seedlings of dominant tree species in
mature forest communities are more highly dependent on
AMF than plants that typically dominate earlier successional
communities, garlic mustard invasion may disproportionately
damage mature forests relative to other habitats.
Results/Discussion
We first tested whether native tree seedlings were less able
to form mycorrhizal associations when grown in forest
understory soils with a history of garlic mustard invasion
than when grown in soils that had not experienced invasions
(Experiment 1). We found that dominant native hardwood
tree species of northeastern temperate forests, Acer saccharum
(sugar maple), Ac. rubrum (red maple), and Faxinus americana
(white ash), showed significantly less AMF colonization of
roots (Figure 1A) and slower growth (Figure 1B) when grown
in soil that had been invaded by garlic mustard. AMF
colonization was almost undetectable in soil that had been
invaded by garlic mustard. These reductions were similar to
those observed when seedlings were grown in sterilized soil
from both garlic mustard–invaded and garlic mustard–free
sites (Figure 1B), strongly suggesting that the mechanism by
which garlic mustard suppresses the growth of native tree
species is microbially-mediated, and not the result of soil
differences or direct allelopathy.
We then conducted additional experiments to confirm that
garlic mustard specifically caused AMF decline in the native
soils (Experiment 2–4). We grew seedlings of the same three
native tree species used in Experiment 1 in uninvaded forest
soils that were conditioned for 3 mo with either garlic
mustard plants or with one of the three native tree species.
All three tree species demonstrated significantly lower AMF
colonization in soils conditioned by Al. petiolata (0%–10%)
than in soils conditioned by the native plants (20%–65%;
Figure 2A). AMF colonization was similar in unconditioned
(control) soils and soils conditioned with native plants. In
addition, growth of the tree seedlings was the lowest in soils
conditioned by garlic mustard (Figure 2B), confirming that
garlic mustard plants reduce native plant performance by
interfering with the formation of mycorrhizal associations.
We investigated whether there is a phytochemical basis to
garlic mustard’s observed antifungal effects on AMF in
Experiments 3–4. In an earlier study, Vaughn and Berhow
<31> isolated the phytotoxic glucosinolate hydrolysis products
allyl isothiocyanate, benzyl isothiocyanate, and glucotropaeolin
from extracts of Al. petiolata root tissues and found
evidence for their allelopathic effects on certain plants in the
absence of mycorrhizas. These phytochemicals could have
direct effects on plant growth through allelopathy as well as
indirect effects via disruption of AMF. To experimentally
establish that garlic mustard’s effect on AMF is phytochemically
based, we grew native tree seedlings on uninvaded soils
to which we added individual aqueous extracts of garlic
Figure 1. Experiment 1
The influence of field soils that were invaded or uninvaded by Al.
petiolata (6 sterilized) on (A) mycorrhizal colonization (Fsugar maple¼77.7,
df¼3,39, p , 0.001; Fred maple¼60.5, df¼3,39, p , 0.001; and Fwhite ash¼ 116.6, df ¼ 3,39, p , 0.001) and (B) biomass accumulation (Fsugar maple ¼ 57.8, df¼3,39, p , 0.001; Fred maple¼61.4, df¼3,39, p , 0.001; and Fwhite
ash ¼ 70.1, df ¼ 3,39, p , 0.001) of native tree seedlings. Bars represent
the mean and standard error.
DOI: 10.1371/journal.pbio.0040140.g001
PLoS Biology | www.plosbiology.org May 2006 | Volume 4 | Issue 5 | e140 0728
Invasive Plant Disrupts Mycorrhizas
mustard or each of the native trees species (Experiment 3).
We found that garlic mustard extract was just as effective as
the living plant at reducing AMF colonization (Figure 3A) and
growth (Figure 3B) of the native plants. Moreover, exposing
AMF spores to extract of garlic mustard severely and
significantly reduced germination rates of those spores
(Experiment 4; Figure 3C). Collectively, our results clearly
demonstrate that garlic mustard, probably through phytochemical
inhibition, disrupts the formation of mycorrhizal
associations. Our results thus reveal a powerful, indirect
mechanism by which an invasive species can suppress the
growth of native flora.
Because plants vary in their dependency on AMF <32>,
garlic mustard’s disruption of native plant–fungal mutualisms
should not inhibit the growth of all plants equally, but rather
should correlate strongly with the mycorrhizal dependence of
species encountered in the invaded range. Specifically,
courser root production, which impedes the nutrient uptake
of typically slow-growing, woody plants such as tree seedlings,
may explain the stronger AMF dependency of certain species
<19,33>. To test whether garlic mustard’s effects correlate with
AMF dependency, and whether garlic mustard has stronger
negative effects on forest tree seedlings than on other plants,
we conducted another experiment (Experiment 5) using 16
plant species for which we determined AMF-dependency by
computing the difference in plant growth in the presence and
absence of AMF. We then tested the impact of garlic mustard
on the AM fungal colonization and growth of each plant
species as above. All 16 plants were successfully colonized by
AMF, and the presence of garlic mustard heavily reduced
AMF colonization in all plants (Figure 4A). However, the
presence of garlic mustard had a much stronger effect on
plants that had high mycorrhizal dependency than those with
less dependency (Figure 4B). The strongest effects were
observed for woody species most typically found in forested
sites. These results indicate that the invasion of garlic
mustard is more likely to negatively impact highly mycorrhizal-
dependent tree seedlings than less-mycorrhizal-dependent
plants. Thus, garlic mustard’s successful
colonization of understory habitat may be attributed in part
to its ability to indirectly suppress woody competitors, and its
effect on the native flora may be more detrimental in intact
forests than disturbed sites. In addition, the data suggest that
invasion by garlic mustard may have profound effects on the
composition of mature forest communities (e.g., by repressing
the regeneration of dominant canopy trees, and by
favoring plants with low mycorrhizal dependency such as
weedy herbs).
In conclusion, our results reveal a novel mechanism by
which an invasive plant can disrupt native communities: by
virtually eliminating the activity of native AMF from the soil
and drastically impairing the growth of native canopy species.
It is currently unclear precisely which phytochemicals
produced by garlic mustard have the observed antifungal
properties, whether and how they interact with other soil
microbes, and whether these anti-fungal effects extend to
other functionally important forest soil fungi such as
ectomycorrhizal fungi and saprotrophic fungi. In addition,
within the home range, it is not known if evolutionary natural
resistance of co-occurring European neighbors may buffer
the effects of garlic mustard’s antifungal properties <34–36>.
Further research in these directions is needed to better
understand the effects of this invader on natural ecosystems
and the mechanisms involved. In North America; however,
the disruption of native tree seedling–AMF mutualisms may
facilitate garlic mustard’s invasion into mature forest under-
Figure 2. Experiment 2
The effect of soils conditioned with garlic mustard Al. petiolata (gm),
sugar maple (sm), red maple (rm), or white ash (wa) on (A) mycorrhizal
colonization (Fsugar maple¼31.2, df¼4,49, p , 0.001; Fred maple¼18.2, df¼ 4,49, p , 0.001; and Fwhite ash¼22.1, df¼4,49, p , 0.001) and (B) increase
in biomass (Fsugar maple¼15.1, df¼4,49, p , 0.001; Fred maple¼18.1, df¼ 4,49, p , 0.001; and Fwhite ash ¼ 13.2, df ¼ 4,49, p , 0.001) of native tree
seedlings. Bars represent the mean and standard error.
DOI: 10.1371/journal.pbio.0040140.g002
Figure 3. Experiments 3 and 4
The effects of extract of garlic mustard (gm), sugar maple (sm), red maple
(rm), white ash (wa), or a water control on (A) mycorrhizal colonization of
native tree seedlings (Fsugar maple¼20.3, df¼4,49, p , 0.001; Fred maple¼ 19.8, df ¼ 4,49, p , 0.001; and Fwhite ash ¼ 25.4, df ¼ 4,49, p , 0.001
), (B) increase in biomass of native tree seedlings (Fsugar
maple ¼ 11.7, df ¼ 4,49, p , 0.001; Fred maple ¼ 14.2, df ¼ 4,49, p , 0.001;
and Fwhite ash¼27.9, df¼4,49, p , 0.001 ), and (C) percent
germination of native AMF spores (FGlomus ¼ 17.3, df ¼ 4,49, p , 0.001;
and FAcaulospora ¼ 21.8, df ¼ 4,49, p , 0.001 ). Bars
represent the mean and standard error.
DOI: 10.1371/journal.pbio.0040140.g003
PLoS Biology | www.plosbiology.org May 2006 | Volume 4 | Issue 5 | e140 0729
Invasive Plant Disrupts Mycorrhizas
story and have particularly negative effects on the growth,
survival, and recruitment of native trees, and the composition
of forest communities.
Materials and Methods
Experiment 1. Using a 15-cm–wide corer, we collected soil from
garlic mustard–invaded and nearby garlic mustard–free locations at
each of five forested areas dominated by Acer rubrum L. (red maple),
Ac. saccharum Marsh. (sugar maple), Fraxinus americana L. (white ash),
and Fagus grandifolia Ehrh. (American beech) near Waterloo, Ontario,
Canada. Invaded and uninvaded sites were randomly chosen within a
40-m2 plot within each forested area. Soils from the invaded and
uninvaded areas were pooled separately in the lab and screened to
remove coarse roots and debris. Half the soil from each pool was then
sterilized by autoclaving at 120 8C to create four soil treatments: (1)
soil with a history of garlic mustard, (2) sterile soil with a history of
garlic mustard, (3) soil without a history of garlic mustard, and (4)
sterile soil without a history of garlic mustard. Six-inch pots were
filled with a 1:1 mixture of sterilized silica sand and one of the four
soil types. To each pot, we added a single seedling (seeds germinated
on Turface , a clay
substrate) of one of the three native overstory tree species (sugar
maple, red maple, or white ash) in a complete 4 3 3 factorial design
with ten replicates of each treatment combination. The initial wet
biomass of each seedling was recorded prior to planting, and dry
weights were estimated using a dry–wet regression calculated from
twenty extra seedlings. Pots were randomly placed on a greenhouse
bench. Plants were watered (400 ml) once per week. Fertilizer was not
added. After 4 mo of growth, shoots and roots were harvested, dried
at 60 8C for 48 h, and weighed to determine biomass. An
approximately 1-g subsample of roots from each seedling was
extracted, stained with Chlorazol Black E <37> and analyzed for
percent colonization by AMF <38>. Biomass and percent colonization
data were analyzed using analysis of variance (ANOVA) for two fixed
effects (soil type and species) and their interaction, followed by the
Ryan-Einot-Gabriel-Welsch (REGW) multiple-range test.
Experiment 2. Using field soil without a history of garlic mustard
invasion (see Experiment 1), we grew garlic mustard, sugar maple, red
maple, and white ash seedlings in separate 6-in pots (n ¼ 10) to
condition the soil to each plant species. After 3 mo of conditioning,
shoots and roots were removed. Unconditioned soil served as a
control to the four plant-conditioning treatments. We added a single
seedling of each of the three tree species to each of the five soil
treatments. Pots were randomly placed on a greenhouse bench. Plants
were watered (400 ml) once per week, without fertilizer. After 4 mo of
growth, plants were harvested, biomass was determined, and percent
mycorrhizal colonization of roots was assessed as in Experiment 1.
Data were analyzed using ANOVA for two fixed effects (species and
soil condition treatment). Means from the three species were pooled,
and the effect of conditioning treatment was tested with a singlefactor
ANOVA followed by the REGW multiple-range test.
Experiment 3. To 6-in pots containing field soil without a history
of garlic mustard (see Experiment 1), we added a one-time, 100-ml
aqueous extract <27> of whole plants of either garlic mustard, sugar
maple, red maple, or white ash. A water control was included to give
five treatments. Whole-plant extract was used to account for
secondary compounds exuded through roots and leaf litter. After 1
wk of exposure to the extract, seedlings of each tree species were
planted in each of these five treatments to give a full factorial design
(extract source 3 tree species) with ten replicates of each treatment
combination. Plants were watered (40 ml) every week, without
fertilizer. After 4 mo of growth, plants were harvested, biomass was
determined, and roots were assayed for mycorrhizal colonization as
in Experiment 1. Data were analyzed by two-factor ANOVA.
Experiment 4. Spores from AMF native to the forest sites were
obtained using trap cultures (as described in <39>, but with a mix of
native plants) of soil samples from the uninvaded locations. We
visually collected and separated Glomus and Acaulospora spores from
these cultures, and compared germination rates of each genus in five
treatments: a water agar control and water agar amended with an
aqueous extract from each of the four plants, as above. Ten randomly
drawn spores were added into each plate, which was then incubated
at 18 8C for 10 d. Ten replicate plates were prepared for each of the
ten treatment combinations (two AMF genera 3 five extracts). Plates
were monitored microscopically for spore germination. Percent
germination data were analyzed using ANOVA for two fixed effects
(extract source and AMF genus), and because of a significant
interaction, each AMF genus was then analyzed separately using
single-factor ANOVA followed by the REGW multiple-range test.
Experiment 5. We investigated the effects of garlic mustard on
woody and herbaceous plants using the following 16 native plant
species: Cichorium intybus, Trifolium repens, Plantago major, and Taraxacum
officinale (dominant herbaceous colonizers of disturbed edges
and bare ground); Solidago canadensis, Chrysanthemum leucanthemum,
Daucus carota, and Asclepias syriaca (dominant herbaceous edge and gap
species); Juniperus virginiana, Populus deltoides, Morus alba, and Prunus
virginiana (dominant woody colonizers of forest edges and gaps); and
Fr. americana, Ac. saccharum, Ac. rubrum, and Pr. serotina (dominant tree
species of mature forest). Seedlings of each plant were transplanted
into 8-in pots. For each species, growth was compared under the
following soil treatments: (1) soil without a history of garlic mustard
and inoculated with AMF, (2) soil without a history of garlic mustard,
without AMF, and (3) soil with a history of garlic mustard, and
inoculated with AMF. Experimental soil was collected within a
mature-canopy maple forest from locations with and without garlic
mustard. Soils from each location type were then mixed, cleaned of
Figure 4. Experiment 5
(A) Effect of mycorrhizal dependency on Al. petiolata reduction of AMF
colonization.
(B) Effect of mycorrhizal dependency on Al. petiolata reduction in plant
growth. Mycorrhizal dependency was calculated separately as the
difference between plant growth in the presence and absence of AMF.
Different colors represent plants with different life-history strategies, as
follows: yellow dot, herbaceous colonizers of disturbed edges and bare
ground; reddish brown dot, herbaceous edge and gap species; blue dot,
woody colonizers of forest edges and gaps; black dot, tree species of
mature forest. Species are labeled as follows (with mean mycorrhizal
colonization in soil not conditioned by garlic mustard 6 standard error
in parentheses): 1¼Ci. intybus (18.5 6 4.1), 2¼Tr. repens (46.7 6 6.3), 3¼ Pl. major (28.2 6 3.7), 4 ¼ Ta. officinale (37.3 6 2.5), 5 ¼ S. canadensis
(48.0 6 6.2), 6¼C. leucanthemum (34.6 6 3.1), 7¼D. carota (40.4 6 6.2),
8¼As. syriaca (52.1 6 5.8), 9¼J. virginiana (31.2 6 4.4), 10¼Po. deltoids
(63.9 6 4.5), 11¼M. alba (38.6 6 5.9), 12¼Pr. virginiana (28.4 6 4.2), 13
¼ Fr. americana (65.9 6 5.3), 14 ¼ Ac. saccharum (46.3 6 3.7), 15 ¼ Ac.
rubrum (59.5 6 5.7), 16 ¼ Pr. serotina (34.8 6 5.5).
DOI: 10.1371/journal.pbio.0040140.g004
PLoS Biology | www.plosbiology.org May 2006 | Volume 4 | Issue 5 | e140 0730
Invasive Plant Disrupts Mycorrhizas
all coarse roots and debris, autoclaved, and added to the pots as a 1:1
mix of soil and silica sand. AMF spores were extracted from field soil
collected from sites representing the four different habitats, and
pooled. The AMF-inoculation treatment consisted of adding 200
randomly picked spores to each pot, 2 cm below the surface, and
beneath the newly transplanted seedlings. Plants were watered (500
ml) once per week, without fertilizer. They were harvested after 4 mo
of growth, dried at 60 8C for 36 h, and weighed to determine biomass.
AMF dependency of each plant species was determined by computing
the difference in plant growth in the presence and absence of AMF,
i.e., contrast of treatments (1) and (2) <32>. The effects of garlic
mustard on plant growth and percent colonization of each plant were
determined by contrasting treatments (1) and (3). To ask whether any
relationships existed among mycorrhizal dependency, life form, and
garlic mustard effects, we performed two regressions: percent
reduction in AMF colonization by garlic mustard on AMF dependency
and percent reduction in plant biomass by garlic mustard on
AMF dependency.
Acknowledgments
We thank T. Denich, V. Grebogi, G. Herrin, P. Hudson, G. Kuenen, J.
Lozi, B. Shelton, P. Stephens, J. Van Houten, and Z. Zhu for technical
assistance, and P. Antunes, G. De Deyn, and M. Hart for helpful
comments on the text.
Author contributions. KAS, RMC, and JNK conceived and designed
the experiments. KAS and JNK performed the experiments. KAS,
SAC, JRP, BEW, RMC, GCT, SGH, DP, and JNK analyzed the data. JNK
contributed reagents/materials/analysis tools. All authors wrote the
paper.
Funding. We thank the Natural Sciences and Engineering Research
Council of Canada, and the Harvard University Bullard Foundation
for financial support.
Competing interests. The authors have declared that no competing
interests exist. &
References
1. Rejma´nek M (2000) Invasive plants: Approaches and predictions. Austral
Ecol 25: 497–506.
2. Mooney HA, Hobbs RJ (2000) Invasive species in a changing world.
Washington (D. C.): Island Press. 457 p.
3. Ewel JJ, O’Dowd DJ, Bergelson J, Daehler CC, D’Antonio CM, et al. (1999)
Deliberate introductions of species: Research needs. Bioscience 49: 619–
630.
4. Mitchell CE, Power AG (2003) Release of invasive plants from viral and
fungal pathogens. Nature 421: 625–627.
5. The´baud C, Simberloff D (2001) Are plants really larger in their introduced
ranges? Am Nat 157: 231–236.
6. Callaway RM, Ridenour WM (2004) Novel weapons: Invasive success and the
evolution of increased competitive ability. Front Ecol Environ 2: 436–443.
7. Hobbs RJ, Huenneke LF (1992) Disturbance, diversity, and invasion:
Implications for conservations. Conserv Biol 6: 324–337.
8. Levine JM, D’Antonio CM (1999) Elton revisited: A review of evidence
linking diversity and invasibility. Oikos 87: 15–26.
9. Keane RM, Crawley MJ (2002) Exotic plant invasions and the enemy release
hypothesis. Trends Ecol Evol 17: 164–170.
10. Levine JM, Vila M, D’Antonio CM, Dukes JS, Grigulis K, et al. (2003)
Mechanisms underlying the impacts of exotic plant invasions. Proc Biol Sci
270: 775–781.
11. Richardson DM, Allsopp N, D’Antonio CM, Milton SJ, Rejma´nek M (2000)
Plant invasions—The role of mutualisms. Biol Rev Camb Philos Soc. 75: 65–
93.
12. Smith SE, Read DJ (1997) Mycorrhizal symbiosis. 2nd edition. New York:
Academic Press. 605 p.
13. Janos DP (1980) Mycorrhizae influence tropical succession. Biotropica 12:
56–64.
14. Grime JP, Mackey JML, Hillier SH, Read DJ (1987) Floristic diversity in a
model system using experimental microcosms. Nature 328: 420–422.
15. Francis R, Read DJ (1995) Mutualism and antagonism in the mycorrhizal
symbiosis, with special reference to impacts on plant community structure.
Can J Bot 73: 1301–1309.
16. Van der Heijden MGA, Klironomos JN, Ursic M, Moutoglis P, Streitwolf-
Engel R, et al. (1998) Mycorrhizal fungal diversity determines plant
biodiversity, ecosystem variability and productivity. Nature 396: 69–72.
17. Vogelsang KM, Bever JD, Griswold M, Schultz PA (2004 June) The use of
mycorrhizal fungi in erosion control applications. Final Report for
Caltrans. Sacramento (California): California Department of Transportation
Contract No. 65A0070. 150 p.
18. Haselwandter K (1997) Soil micro-organisms, mycorrhiza, and restoration
ecology. In: Urbanska KM, Webb NR, Edwards PJ, editors. Restoration
ecology and sustainable development. Cambridge: Cambridge University
Press. pp. 65–80.
19. Read DJ (1991) Mycorrhizas in ecosystems–Nature’s response to the ‘Law of
the minimum.’ In: Hawksworth DL. Frontiers in mycology. Wallingford
(United Kingdom): CAB International. pp. 101–130.
20. Marler MM, Zabinski CA, Callaway RM. (1999) Mycorrhizae indirectly
enhance competitive effects of an invasive forb on a native bunchgrass.
Ecology 80: 1180–1186.
21. Van der Heijden MGA (2004) Arbuscular mycorrhizal fungi as support
systems for seedling establishment in grassland. Ecol Lett 7: 293–303.
22. Nuzzo V (1999) Invasion pattern of the herb garlic mustard (Alliaria
petiolata) in high quality forests. Biol Invasions 1: 169–179.
23. Nuzzo V (2000) Element stewardship abstract for Alliaria petiolata. Arlington
(Virginia): The Nature Conservancy. Available: http://tncweeds.ucdavis.edu/
esadocs/documnts/allipet.html. Accessed 16 March 2006.
24. Blossey B, Nuzzo V, Hinz H, Gerber E. (2001) Developing biological control
of Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard). Nat Areas
J 21: 357–367.
25. Meekins JF, McCarthy BC (1999) Competitive ability of Alliaria petiolata
(garlic mustard, Brassicaceae), an invasive, nonindigenous forest herb. Int J
Plant Sci 160: 743–752.
26. Prati D, Bossdorf O (2004) Allelopathic inhibition of germination by
Alliaria petiolata (Brassicaceae). Am J Bot 91: 285–288.
27. Roberts KJ, Anderson RC (2001) Effect of garlic mustard (Beib. Cavara & Grande)] extracts on plants and arbuscular mycorrhizal
(AM) fungi. Am Midl Nat 146: 146–152.
28. Renwick JAA (2002) The chemical world of crucivores: Lures, treats and
traps. Entomol Exp Appl 104: 35–42.
29. Siemens DS, Garner S, Mitchell-Olds T, Callaway RM (2002) Cost of defense
in the context of plant competition: Brassica rapa may grow and defend.
Ecology 83: 505–517.
30. Schreiner RP, Koide RT (1993) Mustards, mustard oils and mycorrhizas.
New Phytol 123: 107–113.
31. Vaughn SF, Berhow MA (1999) Allelochemicals isolated from tissues of the
invasive weed garlic mustard (Alliaria petiolata). J Chem Ecol 25: 2495–2504.
32. Klironomos JN (2003) Variation in plant response to native and exotic
arbuscular mycorrhizal fungi. Ecology 84: 2292–2301.
33. Newsham KK, Fitter AH, Watkinson AR (1995) Multifunctionality and
biodiversity in arbuscular mycorrhizas. Trends Ecol Evol 10: 407–411.
34. Reinhart KO, Packer A, Van der Putten WH, Clay K (2003) Plant-soil biota
interactions and spatial distribution of black cherry in its native and
invasive ranges. Ecol Lett 6: 1046–1050.
35. Callaway RM, Thelen C, Rodriguez A, Holben WE (2004) Soil biota and
exotic plant invasion. Nature 427: 731–733.
36. Callaway RM, Thelen GC, Barth S, Ramsey PW, Gannon JE (2004) Soil fungi
alter interactions between the invader Centaurea maculosa and North
American natives. Ecology 85: 1062–1071.
37. Brundrett MC, Piche Y, Peterson RL (1984) A new method for observing
the morphology of vesicular-arbuscular mycorrhizae. Can J Bot 62: 2128–
2134.
38. McGonigle TP, Miller MH, Evans DG, Fairchild GL, Swan JA (1990) A new
method which gives an objective measure of colonization of roots by
vesicular arbuscular mycorrhizal fungi. New Phytol 115: 495–501.
39. Klironomos JN, Allen MF, Rillig MC, Piotrowski J, Makvandi-Nejad S, et al.
(2005) Abrupt rise in atmospheric CO2 overestimates community response
in a model plant-soil system. Nature 433: 621–624.

[Arugula Latte]

7. Okay. Now you've bored me, as well ...

:boring:

[BelleCarolinaPeridot]

8. I'm ready to be entertained again.

[greatauntoftriplets]

9. Northwestern lost to Wisconsin today....

Yet again.

[HEyHEY]

10. here

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=105x5709889

[BelleCarolinaPeridot]

11. All of his songs put me to sleep.

[ghostsofgiants]

12. Yeah, that'll do it.

Though I should be careful, last time I called a musician boring someone put me on ignore.