Invasive Ants: Unwanted Partners in Ant-Plant Interactions?

18 Pages·2003·15.2 MB·

by  Lori Lach

INVASIVE
ANTS:
UNWANTED
PARTNERS
IN
ANT-PLANT INTERACTIONS?
(mm
D,.,um., these examples a
.
-en ants and plants from
ratine
facultative, loose associations to s|tecies-s|)ecilic. ne ant can interact directly and
mutualisms, and innumerable same
obligate <|uciioii- e plant multiple ways.
in
lia\e been posed about the costs, benefits, and evo- benefit the plant in one interac-
The
lutionary implications of these relationship- plant in another.
II.
,il
!
(
tie. 1985; Bronslein, 1994; Jolivet, 1996). As in- net outcome for the plant will depend on the rela-
vasive ants spread, their interactions with plants tive balance of a range of interactions, all of which
arc inevitable and have potent iallv great implica- in turn will be influenced bv the same set of vari-
ables that Ivpicallv iiilluence ant-planl interactions.
know
tent are ant-plant interactions altered by the intro- Itimately. vve will want to whether invasive
I
duction of these novel partners? the bala,
)
Invasive ants possess a disbud combination ol enllv
]
(Holway
traits relative to native ants et ah. 2002).
some
In tins per. hypothesize ol the-e hail-
p lli.il
;l
I
and provide a basis for predicting the outcome of
these novel interactions. locus on the potential
loi
I
the approximately 10.000 species of ants
in
( >l
differences between native and invasive ants the
in
the world, about >0 have been introduced around
1
.
way they protect plant- from lierbivorv. tend llo-
the world with the help humans; these may be
ol
moplera. and interlere with plant reproduction.
termed exotic, or tramp ants (McGlynn. '>*>*>). In-
These examples encompass more I
the facultative.
vasive ants are the small subset of introduced ant-
are able establish and penetrate areas out-
that to
increasingly likclv to participate as they spread
side of human-modified habitats (Holway
el al.,
around
the globe.
2002). Well-known examples in the United States
\ltliough explore the dilTei ctiecs between na-
I
in' hide the red imported fire ant, Solenopsis invicta,
i
Symposia
*
pn.y helpful
ii|e.|
I
New
o Corson Hall. Ithaca. York 14853. i.S.A. Ijlt3@
K I
y,
\nn. Missouri Bot. Card. 91-108. 2003.
90:
Garden
Missouri Botanical
The
ami Hie genl inc anl. pilheim/ luimile.
\ I.iiit lit-
I
tlc lire ant. Wasmaniiia aiiropiuielala. the big-head-
ed Pheidole megacephala, and long-legged
ant, anl.
Anoplolepis gracilipes, also appear to be highly s
|]
I i
See Table suniiuaiv of dish
for a ibiilmti-.
1
One
hallmark of invasive ants is their ability to
become extremely abundant new
then- habitats.
in
haps
areas invaded by Solenopsis inricta
I'illall in
&
WO). Lmepithema
(Porter Savignano. humile
I
and megacephala
(Hoi way, 1998). I'heidole (Hoff-
man 1999) have shown the number
et al.. all that
workeis exceeds
of invasive anl greallv thai of na-
tive ants in nearby un-invaded areas. Several
mechanisms
are likelv eonl ribul ig lo invasive Mills"
ii
aehievemenl
nf iiiunerieal Mipoiiorilv including es-
cape from natural enemies and eompetilors and
§
* i f
t 1
-r~
s
changes eoloiiv -Inn hue Inward mil -ned.
in
-< |ii<
-•
1 1 i
niiilli-nesl sii|)ercoloiiies that lack inlra-peeiiic ag-
gression (Holvvay 2002).
et al.,
The physiology and behavior of invasive ants also
likelv plav a role in llieir lenileucv lo achieve high
abundance dom-
(Holvvay et al.. 2(K)2). Kcologicallv
inant arils, including invasive mils such as l.inepi-
nil l*ji
n
ii II ill
i i i | i i ;
to take in more liquid foods, including Moral and
and homopteran honevdew
exlialloral ucclar isnei.
ll
The
1957: Davidson. 1998). ability to harvest these
Mil
oh re-oiuves mav be
le.di lie-rich especiallv
illl-
'
21
lempo
porlanl in liieling ihe high aclivilv ol a large
dvnamir den
workforce, high
ihereliv iiiainlairiitig a
create nests the base of
s tellite at
ill
&
en lending phids (Kaakeh Duleher,
o aggression another
ligh level cliar-
is
non to invas ve ants and likelv enhances
ss as predat rs(Holvvav el al.. 2(H)2). Ac-
lydrale-rieh resources and a
cause and
force are hot the effeel of su-
.
II
I 1
and compel
dilative ilerfereuee mm abil-
il
i
whirl, e anls and other eompetilors
d. ..al
splaeed (Hoi vay 2002).
et al..
documented consequence of an invasive ant H
ily
oduction (Holway 2002). Linepithenm hu-
el al..
for example, has displaced several species of
'.
;aeic ants in California (Erickson, 1971; Ward.
Human
Holway, 1995; Gordon,
1996).
7;
<S
(Cammell Way
1996;
:ugal et al., et al.. 1997).
^
&
South Africa (Donnelly (iiliomee. 1985).
mannia auropunelala has expanded I
territory
its
how
rich food affect they might protect plants from
&
May
Australia (Majer, 1985; Heterick. plant reproduction.
itats in
Hoffman Vanderwoude
2000; ah. 1999; et ah,
et
^minala
2000). Snlmopsis and other ants na-
(¥.) W| R()TKrnoN H ERBIVORKS
n{()M
,
|,
become much
the southern U.S. have less
live to
common &
following iuva-ioii h\ .S. inrirlu (Porter Protection of plants from herbivores perhaps the
is
&
Savignano, 1990; Cotelli Arnetl. 2000). As
est recognized effect of ants on plants. long
()
| ( |
and
Invasive ants also affect other invertebrates
ago as M) i. Chinese citn.s growers facilitated
.„.
x
;
even vertebrates, usually negalivelv. \nopIolcpis
r S ie ad of the yellow citrus ant, which preyed on
p
t |,
blamed diminished populations of &
gracilipes for
is orange orchards (Huang Yang,
1(T )ivores i„ their
| |
K
various invertebrates die Seychelles (Haines
in p Sim e lelK < ahi|i|v ,„ prey on< or simp
)!!7) . . ||1|s
,, i y
Haines. 1978) and generating ecosystem-level
is .. lss wou l-be herbivores has been noted in many
[)a|
] (
changes through impact on the red land crab on &
its
svslems (Beattie. 1085: Holldobler Wilson, 1990).
Christmas Island (Creen ah. 1900). Lim-pithnm,
et
rases p|an|s e an(s food or
,„ S()|nr ,. nti( . )V ()ffering
_ |
some
humile associated with decreases insects
is in ^^ „ one
s|)(i||(i| . F()| . . x ., m[) ._ ;, s [h(m h[ that of {he
^-^ ( | ( ;
California and llawah (Cole ah. 1992: Bolger
in et
,„,. ,,„. pi ,. s( ,, ,. „,- extraflora nec .
l
(
The
ah, 2000). great ,ed„c|,„u .-nd.-m.e „,-
et in
|;mr> mls protection
js (( a(|ra( ., . jn ,. X( ., ia|lf ,t . f()r
,
Hawaii end 1800s
sects lowland the the
,n at ol ^^
|mm m(
|VS (Brnt 1977).
ley,
ir| .,
, ,
^
has been attributed to mvas.on In I'hrululr nu^u- ^^
^ imasive ams
^
^ ((f |rajls ass()< . ia(( , (1 „;,,, ^
(Zimmenn. ^
cephala * .wv u,r,rta has
,.„,
v {q
{
worker and
-i/e. high levels of aeli\ aggressive-
ilv.
nN. rd die southern
in', i-i >-|» |. "-., 'iiai 'iia - in &
s ness (Davidson McKey, 1995: Bronstein. 1998).
Wasmannia
United States (Holwav ah. 2002). au-
el
number workers ma\
large of verv active result
\
ropuiictdta has eliminated or reduced terrestrial in-
in increased plant visitation b\ ants leading to de-
Calapago-
vertebrate populalions the l-land-
in
(Caume
creased herbivory ah. 1997: Bronstein.
et
New
(Lubin, 1984) and Caledonia (Jourdan. 1997).
Caume
1008,: et ah. 1998; Uinsenniair et ah. 2001)
The mechanisms lor these effects are not always
because herbivores are located more rapidly and
some
combination
clear but likelv in\ol\e of prc-
have shorter residence time on the plant (I)uarte
a
&
"'"
Kocha Codov
Hergallo. 1992). Benefits the
to
J'""
some
plant probably level off or even decline at
An
colony however. extremely large colony
size,
\M) Ol
k.omi-.s
<>l
niav imposr a on the plant the ants are steal-
. ()S if
( ,
KACIIONS
ing nectar, tending Homoptera, interfering
floral
enemies
,ialmal herbivores, or excavat-
vvilh ,lu ° f
established that the na- '
ng system. Kesearch determine
the plant's root to
dependent on
ture of ant-plant interactions
is
l
vhere the cost-benefit trade-offs lie with respect to
variables including ant behavior, ant colonv
and stage, host plant attributes, ami the abundance iinl ,ol,,n > si/t ' ,1;,s > el to 1m* (l(>l
\ggressive behav ior also aids
behavior other organisms the svslem
an.) ol in
ph»» herbivores (Fiala ah, 1989; Letour-
'"»»' et
Cash-
(Buckley, 1982; Beattie. 1985; Keeler. 1080;
man, 1991; Davidson & McKey. 1905: Bronstein. '"'an. 1985: Bronstein, 1998). Bentley (1977) re-
laled ant aggression on plants to three factors: pred-
100 1998: Jolivel. 1096). As explained above, in-
1,
"lory hehav ownership behavior or the defense
vasive ants tend have larger colonies and exhibit ior.
to
and swarming
Mo boundaries (Way. 1965),
moie aggressive behavior than nativ e ants. erritorial
over, invasive ants appear to have a stronger lavior or the ability to rapidly recruit workers,
p
may enhanced
many three behaviors be at the colony
dilection than native ants for .!. ,',
,!,
Aggression
resources, which are invariably obtained directly I bv having a large workforce. is
imlirectlv from plants. Since native ants are negatively correlated with proximity to an ants'
f
i
<|uenllv displaced when invasive ants enter a n disturbance near an ants" nest or food source
I:
habilal. will be liail- ol the invad ers that inl elicit a stronger response than a threat en-
it I
The
away
ence outcomes \ppl\ing nlered farther (Way, 1965). vagile, po-
future for the plants.
.
may
isting models ol ant plant inleiacho•ns, (level oii ion- ne^ling bebav ioi ol invasive ants al-
1
them
hypotheses about how invasive ants' levaled abi to nest In closer proximity than a native
<
equatu
the side of the
:ice, left
greater henelit margin for the plant whei
ants are present.
side of the
e
;ft
Ant tending honeydew-producing
of
1
•luding scale, mealybugs, apbids.
&
(Way. 1963; Carroll Jan/cn. 073; l!„eklev.
I
& &
Holldobler Wilson. 1990; Davidson
198,7:
ant would, possibly facilitating a grcalci a^uressive Vie key. l00.- Homoptera extract phloem from the
{).
host plants and excrete as honeydew. Ants feed-
it
Some
ants provide protection from herbivores ing on the honeydew ollen protect llomoplera
die-,,-
while coll. -cting extrafloral nectar. Keeler (1981: from parasites and predators (Wav. 1903: liuckley.
190) modi-led the conditions under which the mu- 1987). The ant-Hon.optera mutualism may be det-
tualism is favored: rimental lor the plant, robbing phloem and
of
it
sometimes leading mold accumulation (Bach,
to
-
D)H]>I.
[A(1
P
1991; Lewis 1976) or phytopathogen
et al.. trans-
=
where
p probability that ants will find the plant. mission (e.g.. pineapple mealybug disease
will
=
=
A
effectiveness of ant-defense. I) effectiveness (Ueardslev et al.. 1982). I'hylophlhora pod rot
- &
of other defense*. intensity of herbivorv. and (Fvans. 1973). swollen shoot virus (Taylor Ade-
II
dovin. 1078)) while conleriing no benefits ex-
in
plants' perspective, the miitualisi change (Ih.ckley. 1987). Less commo.dy. the
inter-
when
may
the left side of the equation, the benefits to action benefit the plant ants deter other
if
&
the plant, exceeds the right side, the costs of at- herbivores while lending Homoptera (Carroll
A &
tracting the ants (Keeler. 1981). schematic of the Jan/en. 1973; Messina. 1981: Compton Robert-
shown
relationship in Figure son. 1988).
is 1.
Given the numerical superiority, attraction to As with plant protection from herbivores, the
common
carbohydrate resources, and aggressive character of characters to many invasive ants will af-
>
we
invasive ants, might expect that fect their Homoptera-lending abilities and conse-
p
mlm
MVi p,
,
.
,
>
A
an( A„„ m Since I) is primarily a factor quently the outcome for the plant. The need for
l imilM „. ..
of the plarrt and the hcibivore(s). and I) carbohydrate resources and ability to harvest co-
I „.
)
are not likely to differ. ll may exceed H„„ if pious amount- o| liquid provides the basis for the
im( . K , 1W .
inlraguild puliation i- a factor, i.e.. ants prev on allraetion ol iuva.-ive ant- |o llomoplera. \nl ag-
il
or inlerlere with the natural enemies of herbivores gression, particularly ownership behavior, an
is ef-
(Fubanks. 2001). However. may be less than
II
,
H„, if invasive ants diminish herbivore popula- pre<lators of Homoptera (Wav. 1963). I'olydomy and
lu
,
tions via direct or indirect interactions that affect nest vagililv may allow invasive ants to reside in
herbivore eggs, larvae, pupae, or adults away from elo-er proximity these carbohydrate resources
to
than would
native ants.
dueible defense (Koptur. 198,9: Ness. 2001) will Ant abundance, however, may be the primary
I,
H
increase with H. For example,
greater affecting inva
if is trail
H
than then extradotal nectaries be may
will in- as affect
im ,. (W . it
mechanisms. Higher numbers may
aut
Iraiislali
be
will greater thai into a higher probability locating the tendees.
ol
C
Homoptera
h
nils a byproduct mutualism with the plant (2a) and when
iii it
ws
indicates the direction of the effect and the positive and
the arrow indicates the strength of the .•Keel. Dotted lines
f
Homoptera, and arc as defined Figure In 2a,
II. \. I) in 1.
doler herl.iv.ire> mi the plant hears the cost of hosting the
h>
and a higher ant homopteran ratio may make ants eeplibilily to phylopalhogens. Other lerms remain
:
=
enemies
inure effective at deterring their partners" the same: p probability thai ants will find the
=
A
(Sleyn. 1955). Tending ants are a limiting resource plant, eflecli\i-nes> nl aiil-.l.Ten-e against
=
honevdew-producing Homoptera many
to in sys- luoii-homopleran) herbivores. effectiveness of
I)
&
Cushman =
tems (Addicott. 197K: Sudd. 1987: Ad- oilier defenses. intensity of (non-homopteran)
II
&
dieott, 1989: Breton Addicott. 1992: Fischer et herbivory. Considering ihe niva-ive ants
trail- ol
2001). and well-tended Homoptera may grow
homopteran
al.. favor high populations, prob-
that is
it
reproduce more and produce more
faster, rapidly, able thai in main cases C,,.,,,^,,,. will be great. -r ihan
young than unten.led ones (Way. 1963: Brislow.
The
probability that the ant finds ihe plant,
Ci,-„
.,„-
a
Where Homoptera
1984; Morales, 2000). the ant
may abundance
vary not only with the of the ant.
:
[t.
becomes Homoptera may become
ratio loo low. ant
Homoptera
|M.s-il>l\ will: the ability of different
lnil
prey or be more easily parasitized or preyed upon &
to recruit ants (Del-Claro Oliveira. 1996). It is
by natural enemies (Way. 1963. and references
unclear, though, whether in\a-i\c ant- may ie-p.>ml
&
Breton Addicott. 1992: Sakata. 1991:
therein:
Hy-
attraetanl en.- differently than native ants.
to
The superabundance achieved
Jolivel. ( by
I') )()|.
pothesized differences and for native
in \.
».
I 1 1
invasive ants may keep the tender: tendee ratio
from below din -hold. such a case,
falling — In
1 1 1 1 with the lood-lor-prolection mutualism involving
we would expect limits the abundance of both
to
mulualists he imposed by the host plant.
to
only be niainlained ihe benefits, in terms of de-
if
may depend
Impacts on the plant. however, also
terred lioinopl. herbivores denoted on the
iioii ijti
Homoptera
on whether the ants tending deter other
side of the equation, exceed the costs exacted
left
hn.
herbivores. byproduct mutualism 2<M)|
In this
.
Homoptera.
on the plant by the the right side of
the plant benefits indirectly from the ants' pres-
exceed
the equation (Fig. 2a). If costs to the plant
Homoptera
from hosted
ence; the ants benefit the
by the plant and possibly the herbivores, they are
if
toward a parasitic relationship with host (Fig.
its
Homoptera
captured as prey. In this scenario. arc
2b). possibly resulting in reduced fitness of the
mod-
analogous extralloral nectaries and Keeler's
to
change
detect any plant
plant. Stu.li.-s that to in
l.iil
can be modified
(1981) as:
el
Homoptera
fitness with outbreaks associated with
- >
D)H C
p[A(l J
h
,
side of the equation (formerly the iu-
it
Seed predalion and Impacts
Inn-resting. ants
of
on disposal and seed prcdation have received
Seed Willi few exceptions Yam.. 1994: s, '«' (1
set. (e.g..
»"»"" attention than impacts on seed myr-
commonly set. In
Puterbaugh, 1998). ants have been
re-
mecochoroiis muliialisiiis. ants disperse seeds away
garded as unwanted guests flowers (Kerncr.
in
Imm
lh "' ollen burying them their
IH78: Buckley. P>f!2). Attracted In floral nectar. <- P 11 1 " P"«»'l- in
eliaosome
ants mav damage floral structures, and depress pol- nvs[. '" «'xclinnge lor the lipid-rich al-
belied m«,I (Buckley. 1082;
to llie Beattie. 1985).
ien viability with their antibiotic secretions (Kerncr.
aL be di>per»ed -eed- iherelore mav ex-ape compe-
18)78: Peakall 1991: (ialen. |000|. \> with
el I
Homoptera and extrafloral neetaiy lending, super- titi() " W1, siblings and parents and are less sus-
'>
abundanee and an <<'I>lible to picdalion and other threats, such as fire
affinity •< -arboh\<lrale resourc-
I'm
may
es combined with levels agression would (bu.kley. 1082: Beattie. 1985). Ants also be
lii-h
..I'
see(l harvesters, consuming the seed Seed
lead to the expectation that invasive ants would be itself.
members harvesters, however, do not eat the seeds they
exceptional recruiting colony flowers all
at to
and mav
and collect, therefore act as accidental seed
exploiting nectar.
floral
&
numerous dispersers (Buckley, 1982: Holldobler Wilson,
aggressive ants are present inflow-
If
1990).
presence may
ers. their affect other floral visitors.
may Various species of ants may be attracted toeliao-
Pollinators be forced reposition frequently
to
somes and opportuuislicalK lake myrme-
to avoid attack by the ants, and this mav result part in
in
mutualisms, whereas
I'ocliorous harvester ants tend
increased transfer of pollen and consequently high-
special adaptations harvesting, consum-
er seed set. Alternatively, pollinators mav avoid the "> ll; '\<- for
m
&
«»"• storing se, -,b loll.lohler Wilson, 1990;
flower altogether, or reposition too superficially for ^-
1 1
Keeler. 1989). In both cases, the ants need
effective pollen transfer, ultimately resulting in de- to (a)
creased seed \' <bseover the seed. recogni/e the seed as a re-
set (Wyatt. 1980). plethora of (!>)
floral
source, and be abb- carry the seed back
antagonists, including pollen consumers, and other (c) to to
florivores, however, may also be deterred, perhaps tlie "<*st. s<^ (l discovery will be dictated by ant
The ants" ultimate impacts on seed be between ant activity and seed availability, and the
set will
dependent on and attractiveness of the eliaosome. present (Beattie,
the attraction availability of if
floral
nectar in the context of the ants' seasonal diet pref- 1985; Keeler. 1989). Seeds are typically high in
and
erences. activity patterns, and abundance, the lipids proteins: recognition of the seed as a
iiuin-
desirable resource may depend on
ber of pollinators and antagonists and the relative
floral their
abundance
susceptibility ant deterrence, structure and and composition of other food sources
to floral
m
defenses against ants, and pollination require- the environment and the dietary requirements of
llie
when
merits of the plant (Kerncr, 1878; Koptur. 1979; the colony the seeds are available (Beattie.
&
K my
Vinson (ireenberg. 1980: Huxley 1991; 1985). In every rinecochorous system studied,
Culler.
&
aL
Klinkhamer de Jong. 1003; an/a 1905; seed-dispersing ants comprise only a small subset
el
I,
&
Koptur Timing. 1008: Pulerbaugh. 1008,), as well the .ml specie* present, and then behavior to-
<>l
ns the relative difference between ants" on ward seeds can vary from one day to the next (Beat-
(-fleets
polhnators and Moral antagonists. Kor example. tie. 1085). suggesting thai recognition of the seed
I
would expect nectar-robbing by invasive ants as a valuable food resource not constant among
to is
have little effect on seed sel across a plant popu- anl species or oyer time for a single species. The
tition for the resource, e.g.. if nectar is available in pend on llie ants" foraging behavior and size and
demand
excess of by pollinators. would expect shape complementarity between seed and Kec-
ant
I (
invasive ants to be more likely to decrease seed set lei. 1080). Harvester ants must also have the man-
in a plant species that has few Moral anlagonisls dibular strength and agililv to ingest the seeds
and is dependent on a few species of small polli- (Beattie. 1085).
How
nators, than in a species that sutlers from many do we expect invasive ants compare
to to
antagonists and has diverse
floral a pollinator guild. native ants in these requirements? Traits of invasive
Moreover. Mowers which
in nectaries are in close ants that have formed the basis lor hypotheses
proximity the stigma and anthers
to relative to
t
paper. namely elevated lance, aggn-ssiou. and ical or physical defenses against .nils. \\ helhei dif-
a!>uii(
much
attraction to carbohvdrali ma\ not have as
•>.
on seed predalion and dispersal. \iimer- ance to phytotoxins, for example, will enabl
infliicm
-e
superiority of invasive ants may increase the certain groups of anls to evade these defenses
it-al i
However,
discover seeds.
probability they will
llial
common
of invasive ants oiler capacity
trails little
lor predicting liou invasive anls will respond to the ml therefore might lack specific (
may
Other be
seeds encounter. that
traits
tliev
may
linked seed discovery and dispersal not vary
to
imidn mcphala
are
lenopsis at-
Inn.
Tisriv; I.vnt
tracted to oilv. lipid-rich lood sources (Vinson cK I'l <)\
•
: i
Greenberg. 1986; Sanders 1992). and seed
et al..
Do observations asive ant-planl iulerac-
&
harvesters occur both genera (Holldobler Wil-
in
comhi-
tions support pred that the distinct
Tims, we might expect these invaders
son. 1990).
outcome
the
will affect
s
some
and even have the
to be attracted to seeds, of
be-
interactions with plants? Specifically,
r
mandibular adaptations helpful for ingesting -rnls.
of their combination of trails, are invasive
more
but perhaps no so than native ants.
lore likely than native anls to deter herbi-
teud llomoplera the detriment of host
to
There
and with plant reproduction?
interfere
>een few direct tests. Most research on ant
been done
with herbivores has in
:tions
noted above, numerical superiority, aggn-s-
how
popula-
n pest
behavi
crop yields are affected by changes in ant
1
account differences
likely to for all
ml has not explored any particular aril at-
ributes influencing the interactions. Still less is
may
vary
t s ants affect seed set, pre-
i
among ants, hut an- unlikely to vary consistently
Nonetheless, examples below
ersal.
among invasive and native ants such as tempera-
vidence of the importance of the
ture tolerance, daily activity patterns, colony cy-
cles, and seasonal preferences for food types will
and
scoring the influence of ant biology the
Kven
certainly affect ants" relationships with plants.
other organisms in the system in determin
single ant species, associations with plants
for a
outcome of these interactions lor the plant.
may change spatially or temporally. For example,
the derive plant protection largely linked to
ol is
which mav change depending
ant foraging patterns,
examples
on the nutritional requirements of the colony (e.g.. ol of invasive
;
and
reproductive cycles), the avail-
in relation to
....
resources
ah. hvi ofein that
ability ol
require less foraging effort than those on the plant
& &
(AM Reagan. 1985: Vinson Green- rarely do they pinpoint any particular characteristic
of interest
&
Rapp Salum. responsible effects on herbivores.
berg, 1986; Stein et al., 1990; ol the ant for
& Some which
can be gained from cases
1995; Cornelius Crave, 1997). insights in
lor example.
Attributes of the potential prey items. flomop- the invader fails to deter herbivores,
tera, and the host plant will also play roles in de- Anoplolcpis gracilipes affords protection from the
fining ant interactions with these organisms (Way. -licking bug. 1,., '.'-' < Inn. i). in Sol-
& omon coconut when reaches high abun-
1963; Cushman, 1991; Huxley Cutler. 1991; Islands
it
when abundant on
Bronstein. 1991). and invasive and native ants mav dance in the trees. But prey are
diverge their responses to these variables as the ground. A. gracilipes fails to forage in the trees
in
Many herbivores (Van Per Coot. 1916; kaak- and premature null. ensues due to A. cocophaga
well. ill
&
eh Dutcher, 1992; Pavis 1992: Cunawar- damage (Creenslade, 1971). In Keeler's (1981)
et al.,
&
&
dena Bandumalhie. 1993; Cornelius Rernays. terms, in this case a high A, ability to deter her-
1995; Montgomery heeler. 2000: Brinkman et bivores, is incou ii H In tin
c\ \\ I I i, i , I i ii il
&
2001) and flowers (Kerner. 1878; Willmer aging on the plant is low.
al.. (p)
chem-
Stone. 1997; Gha/oul. 2090) have effective
reducing the herbivore attack on the
:
other natural
cnt(ili>ti< >
ries are induced by
Several studies have shown
that different invasive inva lative ant's interactions with the her
ants are attracted to \( ;tlh»i ne. lar and can de- and specific the invader
;il ol
. i till*-—, lliat
; i 1 1 1 i J
crease herbivory on
extrafloral nectar-hearing
are
Holway
plants (see 2002. The
et al.. for a review). of extrafloral nectar an
is ir
high population density of Plwidole mrgarcphala system; nectar
extrafloral
r
and
tending of extrafloral nectaries are hlamed response
its to herbivory, therel
for the difference populations of shrnhs between and wasps
in parasitic (Mess
megacephala and
P. native ant-inhabited sites ments have shown
in that
.S.
i
Australian The Vrena
rainforest. native lobata anls and preys on wasps
L. the parasitic
c
and the introduced Senna
nblnsi/alia H.
(I,) S. Il-
Ceratoma catalpae (Hoisdm
little lioni lolivory in area-- invaded by /' megace-
phala. whereas in areas with native ants, the shrubs
k.lv
,\
are small, isolated, and heaviK attacked bv herbi- nectar production coinciding
will) the stage of col-
vores (Hoffman et al.. WO). Other studies dem- ony cycle when workers prefer protein-rich resourc-
I
&
onstrate that Salenapsis inricla (Fleet Young. es. So/rnnp^is inn, la i- apparently as effective a
2000). I.inepithema hnmite (Koptur. and
1070). predator of C. catalpae as are the native ants be-
Wasmaiuaa 00
(iiimpmn
-lala (Meier. I) also are al- cause preys on pupae and pre-pupal iiislars as
1 it
well as larvae, and because of exceptional
ag-
its
inlroduced sometimes
habilal-. to the benefit of the gressiveness when prey are encountered. Thus,
plant. Kill these studies, as with most, do not com- while S. inricla disrupts the mutualism by pre-
pare the behavior of invasive ants
to that of native
do
nor explore
ants, they specific attributes of in- visiting extrafloral and protecting Catalpa
i
vasive- ants that may be influencing the interaction
creased herbivory (Ness. 2001).
Research
exploring
the interact ions of Sol, /, apsis Pulling the example in the c
inricla with Catalpa hignanioides Waller provides (1981) model (Fig. even with
3),
These
der versus herbivore deterrent. studies reveal
both types of outcomes outlined above occur,
that
which ant-Homoptera mutualism
those in the is
para-ilic Inward the plant and those in which the
mu-
ants lending llomopleia enter into a byproduct
ml deterring iion-homopteran
load tualism with the
pi. l.v
be herbivores.
will
1
,
Linepilhema humile^ abundance, aggression,
The
difference
1
duced herbivory and the investment in extradural and tending of aphid* have all been related to its
ability to control populations of the pine p reces-
&
moth (Tlianmrlopoea pilvorampa Den.
present than when native ants are present. sionary
(Way
Porluual pine plantations ah.
worth noting that the probahditv ol lo- Schiff.) in et
p.
is
It
L
on may he inlluenced 1999). The aphids attract foraging humile to pine
cating loraging the plant,
an-
1
crowns, baler the season, pine pioce-.-donarv
tree in
As such, an moth larvae on lives with humile are fiercely
sard offered.
t /..
may attacked, whereas those on native ant-occupied
Solenopsis inrirla
plantations
lives are ignored. oiiseqiienllv. parts of
(
humile escape severe
abundance are inhabited by the
Indeed, high of thai
1982). S. /,.
ir,
pilvnoimpa
been offered as an explanation for the la defoliation caus.-d by '/.' in native ant-
frequency between nec- iuhahiled areas, figures la and b contrast the in-
difference foraging
in its
(Agnew
taried and nectariless isolines of cotton et
ah. 1982). Analogously, is possible that high den- /.. humile are present in terms of Keelers (1981)
it
invaded Cutalpa bignonioi- mo<hlied model derived above.
the
of inrictu in
sity S.
des stand (Ness. 2001) facilitated the ants" foraging
on the plant, notwithstanding the absence of its at- moptera in cacao (Theobroma cacao L.) is a study
traction to extradotal nectar. In these cases, if abi- in contrasts, and illustrates the pos>ibilil\ lor dif-
same
outcomes occur between the plant
diminished
otic or other conditions ever result in ferent to
Wasmannia auropunrlala
may become and West
abundance the invader ant. In Africa.
of S. inrirla.
spread among cacao plantations because
deterring herbivores than ants that actively
less effective at is
deters pestiferous mi bugs despite
may not be as abundant, but are lured to the plants effectively rid
it
and
association with high levels of scale psvllids
its
(Knlwistle. 1972). In contrast, in its native Brazil.
mealybug Planororrus
auropunrlala tends the
If.
mans Homoptera cacao
and other
all (bissol in
i
Lincpilbcma hum Phei- and control p.-| herbivores possibly be-
\noplnlepis grarilipes. He. fails to
dominance
and Wasmannia auropunrlala cause does not always achieve in the
mcaiK-cphtilit.
flulr
it
De Souza
have been noted for their ability to cause Ho- ant mosaic (De Medeiros et ah. 1905: et
all
moplera outbreaks various parts of the world ah. 1998). In the parlance of the modified keeler
in
C
may some- (1081) model, West Africa. the cost to the
(Holway ah. 2002). Solenopsis inrirla in
et
.
h
llomopleia associated with
times obtain carbohydrates directly from plant tis- plant of hosting the 11.
sue (Vander Meer ah. 1905). but also has been auropunrlala. is outweighed by the high A. the
et
associated with increased llomopleia populations ability of W. auropunctata to deter key herbivores,
smd
(lofgren. 1980; Holway ah. 2002). The data col- and the ant can be to have entered a In product
el
auropiinr-
these studies often discern any par- mutualism with cacao, but in Brazil. U.
lected to
in fail
lala lending rim imposes a high and a small
/'.
(.],,
exceeds
Homoptera outbreaks. While some resulting in a cost to the plant that the
responsible for \.
aggro-
abundance,
evidence of the importance of benefit.
megacephalu
Simla! Pheidole native
in its
Iv.
mealybugs. Planororrus
West Africa tends the ritri
my and which arc associated with
examples below, evaluation of prediction that njalensis (l.aing).
I',
these common invasive aul hails play a major role swollen shoot virus in cacao (Taylor Adedoyin.
v\.
determining interactions with plants will be 1978; Campbell, 1994). As part of its tending be-
their
in
enhanced by further detailed study. However, soun- havior. P. megarephala transports soil from the
homoplerans
ground to create tent shelters for the
Plnlopluho-
and thereby acts as vertical vector of
a
anship and
(4a) the Immile-T.
Linc/iilliciuii
|Hll,). Tlie.h.eetioiMil ll indicates the direction of the effect and the positive
row indicates the strength of the Doited
effect. lines
and
igures 2. In la, the native ant nol attracted
is
I
Vl "l>l"'k liiils vy on the major herhi
'">
"i "Umk illustrates inulnaliMii betueeii humilv
II) ili« >|-.mIii.-| aral the pine
I I .\ /..
|
Nr
to the lives aphids and preys on
l>\ /.' pi/rotam/,,, to the Ixtutit of the plant.
Mark
ra spores, eliologie agent of pod
llie mutualism
rot benefits ihe plant
(Kvans, 197:5). In this ease, comprises not only
C,, the introduced range.
this
If
the direct cost of hosting the mealybugs.
also
uld expect studies
(hat that
•
I 1 1 1
associated increased bene
Id.' likelihood of in fee
I
ed with two of the worst diseases of cacao. While
effects of the ants
no cacao studies have ever reported relationships
a. a bl- -.
i-l<
between mrgarrphala
and
homopleraii
\\ m,,m her- Hut
this not
is
t
bivores, it is unlikely that strong deterrence of her- fitness is noted, is usually reported as decreasing
il
bivores (a high A) would have gone unnoticed by (Beallie, 1985; Holway 2002). suggesting
et al.. that
farmers aware
intimately of any effect on their hi most r.ivrs ih, invasi\c nil Imnoptera mutual-
I
Phcldolc megaceplmlus
yields.
fre(|uenl association ism
is parasitic for host plant, beatlie (1085)
its
Homoptera
with high outbreaks
the detriment
to of further points out that the vast majority of data de-
plunt places
Illness firmly in the pest category damage
it in sciilini'j ;in to plants from
lii iii 1. )l« -I is
1|
&
West
Africa (Taylor Adedoyin,
1978). agroeeosyslems.
or other heavily manipulated cn-
between
interaction lomoplera. cacao, and \noplo of Homoptera may be depauperate. Discern-
I (jiiile
Papua New The
lepis gracilipcs in Cuiiieu. ant re- ing whether there are differences how
the inva-
in
sive ant-Hoinoplera mutualism
affects plants the
in
abundance
its (baker. 1972). displaces the native
It
ultural versus less manipulated environments
rii
is
(Room
black pod Smith. 1975; McGregor
rot cv ei dilioiial research.
Moxon, Way &
1985; Khoo.
1992). Moreover, un-
like the ants displaces. ;nu hnia-ses
it 1. L ilipr*.
cocoa weevils and
a<lult persistently disrupts egg
and
laying foraging of several and
inirid eoreid
bugs, all of which are major pests (Knlvvistle, 1972; with exlrafloral nectaries and Homoptera.
the
McGregor & Moxon. Way
1985; Khoo.
1992).
cK
same
but the ant fails to forage in trees in Malay- set. seed dispersal, and seed predalion precludes
cacao and
sian so
is not effective against herbivores attempts to lest the predictions outlined above
at
(Wax khoo.
,\ I , ),'!, )|. indicating that a low p, prob- present. A brief review of the current slate of
ability of finding and lorat-.iirj mi the plant, can knowledge can. however, point early trends and
to
ibility to deter its herbivores. identify areas lor future research.
examples above
ie suggest that ant-llomoptera Although several species of invasive ants have
lalisms that are parasitic on the host plant are been observed
to forage in various (lowers (Adams.
occur
likely to in the invaders' native range. I'>8(.: I.olgrei,. 1080: Bins. 1000; Hara K
llata.