RESEARCH ARTICLE
Polygyny reduces rather than increases nestmate discrimination
cue diversity in Formica exsecta ants
S. J. Martin Æ H. Helantera¨ Æ K. Kiss Æ
Y. R. Lee Æ F. P. Drijfhout
Received: 15 May 2009 / Revised: 2 July 2009 / Accepted: 3 July 2009

Birkha¨user Verlag, Basel/Switzerland 2009
Abstract Although the majority of social insect colonies
are headed by a single queen, some species possess nests
that contain numerous reproductive queens (polygyny), a
trait that is particularly widespread amongst the ants.
Polygyny is often associated with a lack of conspecific
inter-nest aggression between workers. This is hypothesised
to result from increased nestmate cue diversity within nests,
since polygynous nests are more genetically diverse than
monogynous nests. Alternatively, it may reflect the com-
mon origin of polygynous nests that form polydomous
networks. We exploit the recent discovery that the nestmate
discrimination system in the ant Formica exsecta is based
on cuticular hydrocarbons to investigate cue (Z9-alkenes)
diversity in several monogynous and polygynous popula-
tions. Contrary to previous predictions, in all polygynous
populations, the variation between nests in the Z9-alkene
profiles was reduced relative to that found in monogynous
populations. However, nest-specific Z9-alkene profiles
with little variation amongst nestmate workers were still
maintained irrespective of nest type or population. This
suggests a very effective gestalt mechanism that homoge-
nises the chemical discrimination cues, despite genetic
diversity within colonies. Although the reduction in varia-
tion between nests was associated with reduced worker
aggression on the population level, it cannot totally
explain the weak aggression associated with polygynous
populations.
Keywords Formica exsecta
Ants
Polygyny

Cuticular hydrocarbons
Aggression

Nestmate recognition
Introduction
Social insects are notoriously aggressive in defending their
colonies. By identifying non-nestmates, they can exclude
them from their nests (Breed and Bennett, 1987; Jaisson,
1991). Many social insect colonies are founded by a single
queen (monogyny) and remain monogynous throughout the
nest life cycle, but some species possess colonies con-
taining numerous reproductive queens (polygyny), a trait
that is particularly widespread amongst the ants (Heinze,
2008). In ants, the number of queens is an evolutionarily
labile trait and has evolved polyphyletically (Ho¨lldobler
and Wilson, 1977). Polygyny is proving to be more com-
mon among ants, than previously thought, and occurs in
around half the European species (Buschinger, 1974),
indicating that there may be strong benefits associated with
polygyny, especially in saturated habitats where indepen-
dent colony founding is difficult (Rosengren and Pamilo,
1983) or in habitats where polygyny is an adaptation to
S. J. Martin (&)
Y. R. Lee
Department of Animal and Plant Sciences,
University of Sheffield, Sheffield, UK
e-mail: s.j.martin@sheffield.ac.uk
H. Helantera¨
Department of Biological and Environmental Sciences,
University of Helsinki, PO Box 65, Helsinki 00014, Finland
K. Kiss
Department of Horticulture, Sapientia Hungarian University
of Transylvania, Op.9, P.O. Box 4, 540485 Tirgu Mures,
Corunca, Romania
F. P. Drijfhout
Chemical Ecology Group, Lennard-Jones Laboratory,
School of Physical and Geographical Sciences,
Keele University, Keele, UK
Insect. Soc.
DOI 10.1007/s00040-009-0035-z Insectes Sociaux

disturbance, frequent nest removals and fragmentation
(Ho¨lldobler and Wilson, 1977).
Polygyny affects nestmate recognition, and the loss of
inter-nest aggression has long been associated with a loss
of the nestmate discrimination system (Starks et al.,
1998; Stuart, 1988; Stuart and Herbers, 2000; Brown
et al., 2003). But, it is important to distinguish two
separate processes here. First, assuming recognition cues
are at least partly genetically determined, having multi-
ple reproducing queens increases the genetic diversity of
a nest, and consequently the diversity in cues. Increase
in cue diversity within nests is likely to cause cue
overlap amongst colonies and decrease the accuracy of
nestmate recognition, even resulting in the total lack of
nestmate recognition ability. The low intra-nest related-
ness among workers, caused by polygyny, may lead to
considerable variability in worker-produced odour cues
(Peeters, 1988; Satoh and Hirota, 2005), which could
result in low levels of aggression as nestmate recognition
is lost. The degree of the effects of polygyny depends on
the strength of the gestalt. The ‘gestalt nest odour’ is the
bouquet shared by all nestmates through the communal
sharing of odours via grooming and trophallaxis (Crozier
and Dix, 1979). The stronger the gestalt in a nest, the
less is the genetic diversity reflected in variation amongst
nestmate workers. At one extreme, the gestalt odour is
shared by all individuals, and at the other, each indi-
vidual carries a distinct profile. Second, polygyny is
often associated with polydomy, where several nests
remain interconnected by continuing to exchange work-
ers after a budding event (Debout et al., 2007; Ku¨mmerli
and Keller, 2007). In polydomous colonies, the lack of
aggression between neighbouring colonies reflects their
common origin (Helantera¨ et al., 2009). At an extreme,
the whole local population may consist of a single
supercolony of peacefully interacting nests. However,
workers in such colonies may still recognise and reject
individuals from outside the supercolony, so nestmate
recognition is not lost when viewed at a larger scale.
Insect cuticular hydrocarbons (CHCs) are widely
believed to be responsible for encoding the nestmate dis-
crimination system in ants (Singer, 1998; Howard and
Blomquist, 2005), and this has recently been supported by
empirical studies with ants (Akino et al., 2004; Ozaki et al.,
2005; Martin et al., 2008a; Guerrieri et al., 2009). Studies
on Drosophila have shown that CHC production is under
strong genetic influence (Ferveur and Jallon, 1996; Coyne
et al., 1999; Savarit et al., 1999; Dallerac et al., 2000;
Takahashi et al., 2001), as also appears to be the case in
Formica ants (Beye et al., 1998, 2004; Martin et al.,
2008b). Environmental factors can also influence the CHC
profile, e.g. n-alkanes were increased in ants exposed to
high temperatures and low relative humidity (Wagner
et al., 2001), and the amount of n-alkanes were consistently
higher in foragers than in non-foragers of five ant species
including F. exsecta (Martin and Drijfhout, 2009). As we
know that the nestmate recognition system in F. exsecta, a
species with both monogynous and polygynous forms, is
based on the ratio of Z9-alkenes (Martin et al., 2008a), the
aim of this study is to directly investigate the effects of
polygyny on nestmate recognition in the two scenarios:
first, whether increased genetic variation leads to increased
profile variation among nestmates (intra-nest variation), a
loss of nestmate recognition and lack of conspecific inter-
nest aggression; second, whether polygynous populations
lack inter-nest aggression because of polydomy.
Materials and methods
Study species
During 2005–2007 worker ants of F. exsecta were col-
lected from nests e.g. distinct mounds, at several different
locations across Europe (Table 1). A population is a col-
lection of distinct nests that occur over a small or large area
(see Table 1). The six populations consisted of three nest
types that were based on genetic data for four populations
and direct observation of multiple queens in French
F. exsecta study populations (Table 1). In F. exsecta, the
polygynous nests can form supercolonies, i.e. nests are not
independent from each other.
Aggression bioassays
The level of ant aggression was recorded using a five-point
scale: 1, ignore; 2, antennation; 3, mandible gaping; 4,
attack; 5, fighting, sustained biting, etc. Then an aggres-
sivity index was calculated by:
Aggressivity index
¼ Total number of interactions scoring 3; 4 or 5
Total number of interactions
Aggression bioassays recorded interactions between two
nestmates or two conspecific non-nestmates originating
from five different nests within the same population, with
the exception of the Romanian population where 71
different combinations using nests that where less than
30 m apart and 102 different combinations using nests
from 70 to 1,000 m apart were performed. When two
F. exsecta workers are placed in a neutral arena such as a
Petri dish, they tend to simply avoid each other. However,
fights are initiated rapidly if a worker from a monogynous
nest is placed on the surface of a foreign monogynous nest
(Martin et al., 2008a). Therefore, all bioassays were carried
out in the field by placing individual test ants one at a time
S. J. Martin et al.

onto a foreign nest fragment (part of the mound containing
50–100 workers in a box) and recording the outcome of the
first five interactions. Each nest combination was repeated
five times (six times in Romania) using different ants,
giving a total of 25 or 30 recorded interactions for each pair
of nests.
Aggressivity indices were compared using Mann–
Whitney U tests, and means were compared using a t test.
All tests were carried out using SPSS v.14 and P values
were based on the asymptotic significance (two tailed). The
variation in alkenes within each population or nest type
(polygynous vs monogynous) was illustrated by comparing
the proportion (%) of each alkene across all ants belonging
to each group in box plots. The variation in alkenes within
nests, represented by the SD, was compared across popu-
lations and colony types. In both cases, the variation was
illustrated as box plots showing the sample minimum,
lower quartile, median, upper quartile and sample maxi-
mum values.
Chemical analysis
Individual ants were placed into glass vials with 50 ll of
HPLC-grade hexane. After 10 min, the ants were removed
and the hexane evaporated. Vials were then sealed and
stored at 5C. Just prior to analysis, 30 ll of hexane was
added to the vials and the sample analysed on an HP 6890
GC (equipped with an HP-5MS column; length: 30 m; ID:
0.25 mm; film thickness: 0.25 lm) connected to an
HP5973 MSD (quadrupole mass spectrometer with 70-eV
electron impact ionisation). Samples were injected in the
splitless mode and the oven was programmed from 70 to
200C at 40C/min and then from 200 to 320C at 25C/
min and held for 2 min at 320C. Helium was used as the
carrier gas, at a constant flow rate of 1.0 ml/min. CHCs
were characterised by the use of standard mass spectrum
databases, diagnostic ions and their Kovats indices. We had
previously determined by DMDS derivatisation that the
alkene double bond was at the 9th cis (Z) position in F.
exsecta (Martin et al., 2008b).
Chemical data analysis
Previous studies of monogynous F. exsecta populations
revealed several key properties of the CHC profile that led
ultimately to the discovery of the Z9-alkene-based nestmate
signal in this species (Martin et al., 2008a) and the role of
the n-alkanes (Martin and Drijfhout, 2009) that together
account for more than 90% of the CHC profile. Therefore,
within every nest, we investigated if the number of ions of
successive compounds within each homologous series
(n-alkanes and alkenes) was highly correlated to each other
or not. A homologous series is a group of organic com-
pounds with a similar general formula, due to the presence
of the same functional group. In insects, CHC biosynthetic
pathways always produce homologous series, in which
successive hydrocarbons increase by chain lengths of two
carbons e.g. C25:1, C27:1, C29:1, with odd chain-length series
always dominating over even-chain lengths (Lockey, 1991).
It is already known that in monogynous F. exsecta nests, the
amounts of n-alkanes and alkenes are independent i.e.
poorly correlated (Martin and Drijfhout, 2009). The data for
each individual was stored in three forms; (1) the relative
amounts of each compound reported as the number of ions
contained beneath the peak, (2) the proportion (%) of each
alkene calculated by using the total number of ions
belonging only to the same homologous series and not all
CHCs as is normal (see Martin and Drijfhout, 2009) (3) the
transformed proportions using the method of Aitchison
(1986). These three data blocks were arranged in Micro-
soft Excel spreadsheets so that correlations among
compounds based on the number of ions (data block 1)
Table 1 The location, population type and sample size of each Formcia exsecta population studied along with known levels of intra-nest worker
relatedness (R)
Location R Distance between the
furthest nests (km)
No. of colonies and
individuals (n) analysed
Population type
Southern Finland, Hanko – 30 10 (50) Monogynous, monodomous
Southern Finland, Joska¨r Island 0.75a 0.2 10 (50) Monogynous, monodomous
Romania, Voslobeni, Harghita County 0.22b 2 12 (60) Polygynous, polydomous
Southern France, Lyon – 0.2 5 (25) Polygynous, polydomous
Scotland, Highlands, Carrhouse \0.45c 1 12 (96) Polygynous, monodomous
Scotland, Highlands, Glenmore \0.45c 1 8 (77) Polygynous, monodomous
a Martin et al. (2008a)
b Goropashnaya et al. (2007)
c Dallas et al. (2001)
Nestmate cues in polygynous Formica exsecta

could be compared across individuals from the same colony
or species, by plotting the values on a scatter graph
and using the linear trend line function to calculate the r2
value. We compared the three most abundant n-alkanes
and alkenes. The chemical distance among monogynous
F. exsecta colonies was measured by performing a dis-
criminate analysis (SPSS v. 14) on the transformed alkene
proportions and measuring the distance between the colony
centroids and correlating these with the corresponding
aggression index.
Results
Nest aggression and variation in the alkene profile
amongst nests
Amongst the six F. exsecta populations, a consistent pat-
tern emerged. The two monogynous populations were
highly aggressive towards non-nest mates (Fig. 1c) and
possessed the greatest inter-nest variation in their alkene
profile (Fig. 1a, b). In contrast, the four polygnous popu-
lations were not aggressive towards non-nest mates, and
their inter-nest alkene profiles showed a smaller degree of
variation (Fig. 1a, b). This finding still holds when nest
types (monogynous vs polygynous), irrespective of loca-
tion, were compared, that is, there is more alkene variation
amongst nests within the two monogynous population
combined from Southern Finland than the alkene variation
amongst nests within all four polygynous populations
combined (Fig. 2). This is even more impressive when
considering that the two monogynous populations come
from one location (Southern Finland), whilst the polygy-
nous populations comprise nests from populations that
are geographically very distant e.g. Romania, France and
Scotland.
The aggression index within the Romanian population
was the same in nests that were located within 30 m (\1%)
or further than 70 m (1.4%), i.e. aggression was low
regardless of the distance. In contrast, aggression was high
amongst all colonies in the monogynous population, and
there was no significant correlation (r2 = 0.0007, P = 0.9,
n = 10, Pearson) between chemical distance and aggres-
sion index in them. That is, though chemically similar,
F. exsecta colonies (e.g. Fig. 1 colonies 35 vs 71) remain
as highly aggressive ([90%) towards each other as two
nests (e.g. Fig. 1 colonies 53 vs 60) with very different
profiles ([90%).
The CHC profile of all individuals within each nest
irrespective of the number of queens (monogynous or
polygynous) shared the same fundamental characteristic,
that is, a colony-specific distribution of alkenes that are
all highly correlated to each other. Therefore, between
nestmates in all nests, the relative amounts of alkenes,
e.g. C23:1 to C25:1 and C25:1 to C27:1, were always highly
correlated (r2 [ 0.9), whereas the n-alkanes were less
correlated (Table 2). This indicated that the number of
queens does not affect the production of a colony-spe-
cific alkene profile, i.e. does not increase the variation
between nestmates. However, at the population level,
these nest-specific alkene profiles are highly variable
among monogynous nests, but show much less variation
among polygynous nests and populations (Figs. 1, 2).
Comparison of intra-nest variation in alkenes between
monogynous and polygynous populations
The variability among nestmates of the three major
alkenes was compared between populations and nest types
(M vs P). The intra-nest alkene variability is represented
by the standard deviation of each alkene (e.g. C23:1, C25:1
and C27:1) calculated from the profile of five to ten
nestmates. The SD values were then grouped according to
population and showed similar levels of variability across
all populations (Fig. 3). The data were also grouped into
polygynous and monogynous nests and analysed. Contrary
to expectation, the nestmate variation (SD) of the three
major alkenes was not significantly different (C23:1,
t58 = -1.79, P = 0.08; C25:1, t58 = -1.96, P = 0.05;
C27:1, t58 = 2.01, P = 0.05) between polygynous and
monogynous colonies. Therefore, the variation in the
amount of alkene among nestmates is not affected by the
number of queens. However, nest-specific profiles still
exist in both monogynous and polygynous populations,
because the level of nestmate variation (1–3%) is much
smaller than inter-nest variation in both types of popula-
tions (Figs. 1, 2).
Discussion
Contrary to previous predictions (Ho¨lldobler and Michener,
1980; Keller and Passera, 1989), we found no increase in
the diversity of odour cues amongst nestmates in polygy-
nous colonies. Thus, less efficient nestmate discrimination
in the polygynous F. exsecta populations is not due to
increased cue diversity, causing more acceptance errors
than in less genetically diverse monogynous colonies
(Starks et al., 1998; Brown et al., 2003). Furthermore, we
found that amongst nestmates, alkene variation is similar in
polygynous and monogynous colonies (Fig. 3), since an
increase in the number of queens does not prevent the
nestmates from obtaining or producing a highly correlated
distribution of alkenes.
S. J. Martin et al.

Pr
op
or
tio
n
(%
) o
f (Z
)-9
-al
ke
ne
s
C 23:1
C25:1
C27:1
C29:1
C31:1
C 21:1
Nest
mates
Non-nest
mates
A
ggression index (%
)
0
20
40
60
37 13 31 42 30 36a 32 16 36b 33 19 1
0
60
0
1
0
60
A D B E C
0
20
40
60
0
1
0
60
GH GC GG GB GE GA GD GF0
20
40
60
0
1
0
60
0
1
0
60
56 60 8 22 35 71 64 53 69 40
0
20
40
60
0
1
0
60
J D C IB H G F E A
0
20
40
60
C23:1
C25:1
C27:1
C29:1
C31:1
C21:1
a b c
Southern Finland mainland population (M)
Southern Finland island population (M)
Romanian population (P)
French population (P)
CC CA CB CE CF CD CI CL CG CK CM CH0
20
40
60
UK Scottish Carrhouse population (P)
UK Scottish Glenmore population (P)
0
1
p <.0001
p <.0001
n.s.
n.s.
n.s.
n.s.
C 19:1
C19:1
Fig. 1 Data from two F. exsecta monogynous (M) and four
polygynous (P) populations. a The alkene profile for each population.
Nests are identified by a letter or number. b The degree of spread of
each alkene within each population. c The level of intra- and inter-
nest aggression among workers. Significance levels were determined
by Mann–Whitney U tests
Nestmate cues in polygynous Formica exsecta

In this study, monogynous F. exsecta nests that had
very similar profiles remained highly aggressive towards
each other, but all polygynous nests irrespective of any
profile differences showed no aggression. This is true for
both polydomous F. exsecta, where nests are parts of the
same supercolony, and also in the polygynous, mono-
domus F. exsecta Scottish populations, where each nest is
a separate entity. The lack of aggression amongst poly-
gynous nests despite potentially detectable differences in
CHC profiles raises the possibility of a lack of aggression,
despite recognition. Lack of aggression could stem from
two different scenarios. First, in polydomous F. exsecta,
the lack of aggression between polygynous nests in
polydomous colonies probably reflects the supercolonial
networks of nests. Even if polygynous nests have
more than 100 queens (Rosengren et al., 1993), and the
relatedness within nests in a supercolony approaches
zero, the nests originate through budding and are likely to
share a common ancestry from a few foundress individ-
uals (Helantera¨ et al., 2009). This notion is supported by
the low numbers of mitochondrial haplotypes within
supercolonies (Seppa¨ et al., 2004), and is reflected in
the chemical similarity between nests and low within-
population diversity, compared to monogynous popu-
lations.
Second, if either monodomous or polydomous colonies
are isolated from other colonies, non-colony mates may be
rarely encountered and, to avoid rejection errors, a per-
missive threshold is applied to all individuals. This results
in the acceptance of individuals from different nests of the
same supercolony, or outside the supercolony, even if they
have different profiles. Workers respond differentially
towards nestmates and conspecific non-nestmates, but
show little or no aggression in polygynous populations of
F. paralugubris (Chapuisat et al., 2005) and the mono-
gynous ant Lasius austriacus, despite the colonies having
their own distinctive CHC profiles (Steiner et al., 2007). It
is known that the variation in relatedness has no influence
on the conspecific discrimination ability of the two Rhyti-
doponera ant species (Crosland, 1990; Peeters, 1988) or in
the ant F. selysi (Rosset et al., 2007). These studies all
indicate that a lack of aggression does not necessarily result
from a loss of the nestmate discrimination system. There-
fore, the relationship between polygyny, discrimination
cues and aggression is not as simple as has been previously
thought, and unravelling this relationship will need more
detailed behavioural observations at two levels. First, the
careful quantification of polydomy is a necessary back-
ground information for interpreting aggression bioassay
results. Second, aggression bioassays should be carried out
so that the possibility of recognition without aggression is
taken into account.
Surprisingly, polygynous colonies, even from differ-
ent locations, were more similar to each other than
monogynous colonies relatively close to each other. The
reduced diversity of discrimination cues in polygynous
and polydomous populations combined relative to mono-
gynous populations (Figs. 1, 2) could reflect the small
number of foundress individuals from whom each
60
40
20
0
C21:1 C23:1 C25:1 C27:1 C29:1 C31:1 C21:1 C23:1 C25:1 C27:1 C29:1 C31:1
Pr
op
or
tio
n
(%
) o
f Z
9 a
lke
ne
s
a b
Fig. 2 The overall range of proportions of each alkene obtained from
ants belonging to a F. exsecta monogynous populations (Southern
Finland) and b F. exsecta polygynous populations (France, Romania
and Scotland). This illustrates that C23:1 and C27:1 have a much larger
range in monogynous than polygynous populations even when all
populations of the same type are combined
Table 2 The mean intra-nest (±SD) level of correlation (r2) between
the three major successive alkenes (C23:1, C25:1 and C27:1) or n-
alkanes (C23, C25 and C27) for each monogynous (M) or polygynous
(P) population
Population Z9-alkenes n-alkanes P
Finland, mainland (M) 0.96 ± 0.03 0.88 ± 0.14 0.04
Finland, island (M) 0.99 ± 0.01 0.72 ± 0.23 \0.01
Romanian (P) 0.96 ± 0.06 0.72 ± 0.30 \0.01
French (P) 0.98 ± 0.02 0.76 ± 0.27 \0.01
UK, Carrhouse (P) 0.98 ± 0.01 0.91 ± 0.10 0.06
UK. Glenmore (P) 0.96 ± 0.04 0.91 ± 0.09 0.08
The t test was used to investigate if the there was a significant dif-
ference in the levels of correlation between the alkenes and n-alkanes
S. J. Martin et al.

supercolony originated. However, this does not explain
why the polygynous colonies, in very separate locations,
are similar to each other. The alternative explanation is
that the lack of within-supercolony genetic structuring
brings the gestalt odour close to a species mean.
Reversion to a species-specific profile could benefit
the nests, since there is always selection, acting to
maintain the species recognition cues even if nestmate
cues are lost. The lack of nest-specific profiles in
polydomous–polygynous populations seems to have
resulted in the profile reverting to a species-specific
one, and despite large geographical distances; these
simple profiles remain remarkably invariant (Fig. 4).
For example, if a very distinctive nest profile, even if
good for nestmate discrimination, was atypical for the
species, it would be selected against in a mating con-
text, if we assume that young queens and males share
the gestalt odour of the nest. Thus, an optimal profile
would allow nestmate recognition, but still be close
enough to a species-specific mean profile to guarantee
mating success. For example, in F. exsecta, the colony-
specific profiles arise from changing the alkene ratio to
the right (C27:1) or left (C23:1), whilst the proportion of
C25:1 remains relatively stable across all nest types
(Figs. 2, 4). The extent of nest variation may well be
constrained by their species profile, since other sym-
patric species such as F. lemani, F. candida and F.
japonica (type2) (Akino et al., 2002) all have similar
Z9-alkenes-rich CHC profiles (Fig. 4), often occupying
the same or adjacent habitat patches and potentially
having simultaneously mating flights. Thus, avoiding
mating with the wrong species is a relevant evolu-
tionary pressure and so maintaining a species-specific
signal is important.
The reduction in signal diversity within a nest, i.e.
maintaining a gestalt odour, may help explain why there
is very little empirical evidence that nepotism occurs in
polygynous ant colonies (Carlin et al., 1993; Snyder,
1993; Keller, 1997) where the queens may or may not be
related (Pamilo, 1982). The low levels of among-nest-
mate variation found in monogynous as well as poly-
gynous and polydomous colonies suggest that the gestalt
mechanism works very efficiently to overcome genetic
diversity and frequent movement of individuals between
nests in polydomous colonies (Katzerke et al., 2006).
The mechanisms that help maintain recognition of nest-
mates from outsiders may thus prevent the ants from
discriminating among nestmates and suppress potential
conflicts.
4
3
2
1
0
4
3
2
1
0
4
3
2
1
0
C 2
3:
1
(%
)
C 2
7:
1(%
)
C
25
:1
(%
)
Fi
nl
an
d
(m
ain
lan
d)
M
Fi
nl
an
d
(is
lan
d)
M
R
om
an
ia
P
Fr
en
ch
P
U
K
C
ar
rh
ou
se
P
U
K
G
le
nm
or
e
P
Fig. 3 Box plots of the standard deviation values obtained for each
nest i.e. based on five to ten individuals, for each of the three major
alkenes (C23:1, C25:1 and C27:1). The range of SD values for each F.
exsecta monogynous (M) or polygynous (P) population is shown. This
illustrates that the level of intra-nest variation of the three major
alkenes is similar amongst all six populations
b
Nestmate cues in polygynous Formica exsecta

Acknowledgments Many thanks go to Liselotte Sundstro¨m of
Helsinki University for allowing access to the F. exsecta study pop-
ulation and Duncan Jackson for his detailed comments. Funding for
S.J.M. and F
P.D. was provided by NERC (NE/C512310/1) and to
H.H. and L. Sundstro¨m by the Academy of Finland grants (213821;
121078 and 206505), respectively.
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0
10
20
30
40
50
60
70
80
F. lemani (P) F. candida(P) F.japonica (type 2)
Pr
op
or
tio
n
(%
) o
f Z
9-a
lke
ne
s
F. exsecta (M) F. exsecta (P)
C19:1
C21:1
C23:1
C25:1
C27:1
C29:1
C31:1
Fig. 4 The mean Z9-alkene profiles based on 57 F. exsecta nests (this
study), 35 F. lemani nests (Martin et al. 2008b and unpublished data),
three F. candida nests (Martin et al. 2008b) and F. japonica (Akino
et al. 2002). Each species has its own unique species-specific alkene
profile that may define the limits of the nestmate recognition signal.
The error bars represent the SD, P polygynous, M monogynous
populations
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