# Full Text: AntGenetics

> Extracted from `2016_AntGenetics.pdf`

---

## Page 1

NE39CH03-Gordon
ARI
25 March 2016
13:12
R
E
V
I
E
W
S
I
N
A
D
V
A
N
C
E
Ant Genetics: Reproductive
Physiology, Worker
Morphology, and Behavior
D.A. Friedman and D.M. Gordon
Department of Biology, Stanford University, Stanford, California 94305-5020;
email: dmgordon@stanford.edu
Annu. Rev. Neurosci. 2016. 39:41–56
The Annual Review of Neuroscience is online at
neuro.annualreviews.org
This article’s doi:
10.1146/annurev-neuro-070815-013927
Copyright c⃝2016 by Annual Reviews.
All rights reserved
Keywords
ants, behavioral genetics, collective behavior, gene expression, epigenetics
Abstract
Many exciting studies have begun to elucidate the genetics of the morpho-
logical and physiological diversity of ants, but as yet few studies have in-
vestigated the genetics of ant behavior directly. Ant genomes are marked
by extreme rates of gene turnover, especially in gene families related to ol-
factory communication, such as the synthesis of cuticular hydrocarbons and
the perception of environmental semiochemicals. Transcriptomic and epi-
genetic differences are apparent between reproductive and sterile females,
males and females, and workers that differ in body size. Quantitative genetic
approaches suggest heritability of task performance, and population genetic
studies indicatea genetic association with reproductivestatus in some species.
Gene expression is associated with behavior including foraging, response to
queens attempting to join a colony, circadian patterns of task performance,
and age-related changes of task. Ant behavioral genetics needs further inves-
tigation of the feedback between individual-level physiological changes and
socially mediated responses to environmental conditions.
41
Review in Advance first posted online  
on April 4, 2016. (Changes may  
still occur before final publication  
online and in print.) 
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 2

NE39CH03-Gordon
ARI
25 March 2016
13:12
Heritability:
Resemblance between
parent and offspring
with regard to some
phenotypic trait.
Heritability can
include nongenetic
mechanisms of
intergenerational
transmission
Contents
INTRODUCTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
42
COMPARISONS AMONG SPECIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
42
MALES AND FEMALES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
REPRODUCTIVE AND STERILE FEMALES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
44
QUEEN NUMBER. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
46
WORKER BODY SIZE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
47
BEHAVIOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
Heritability of Task Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
Worker Behavior in the Absence of a Queen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
48
Age-Related Changes in Gene Expression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
49
Circadian Rhythms and the Foraging Gene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
49
CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
50
INTRODUCTION
Social insect colonies provide compelling examples of collective behavior without central control.
The study of collective behavior in ants seeks to explain how interactions among individuals allow
colonies to regulate their behavior in response to changing conditions. Recent methodological
advances have opened many new opportunities for studying the genetics of ant behavior. All known
species of ants are eusocial, consisting of one or more reproductive females and a large number
of sterile, female workers. Many recent studies have investigated the genetics of reproductive
physiology and of morphological diversity in ants. Here we review the literature on ant genetics
and suggest that despite many recent exciting results, few studies have investigated the genetics
of ant behavior directly.
The review is divided into sections according to the phenotypic traits considered. We first con-
sider studies that are not concerned directly with behavior: comparing families of hymenopterans,
species of ants, males and females, molecular differences associated with female reproductive status,
and workers that differ in body size. In the final section, we discuss genetic studies that investigate
individual behavioral traits directly, including task performance and circadian activity patterns.
Within each section, we discuss a variety of methods. These include quantitative genetic ap-
proaches that examine heritability due to genetic, epigenetic, or environmental sources (Visscher
et al. 2008; reviewed in Linksvayer 2015); phylogenetic analyses of DNA sequence homology
(reviewed in Libbrecht et al. 2013); transcriptomic studies that measure patterns of cellular RNA
abundance, corresponding to gene expression (e.g., Linksvayer et al. 2012); epigenetic studies of
the regulatory mechanisms underlying activation and repression of specific regions of chromatin
(reviewed in Yan et al. 2014, Glastad et al. 2015); and finally, physiological studies of traits such
as enzyme activity (Noble et al. 2014).
COMPARISONS AMONG SPECIES
The genomic analysis of the evolution of colonial living and eusociality in social insects is a rapidly
growing area of research (reviewed in Toth & Robinson 2007, Johnson & Linksvayer 2010,
Linksvayer et al. 2012, Rittschof & Robinson 2014, Rehan & Toth 2015). Most eusocial insect
species are within the order Hymenoptera, a large group with two suborders: Symphyta (sawflies)
and Apocrita (ants, bees, and stinging wasps). Genomic studies have sampled broadly across the
42
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 3

NE39CH03-Gordon
ARI
25 March 2016
13:12
Gene turnover:
Patterns of gains and
losses of protein-
coding genomic loci
over evolutionary time
order, allowing for phylogenetic comparisons among taxa (e.g., Gadau et al. 2012, Johnson et al.
2013, Libbrecht et al. 2013, Nygaard & Wurm 2015). The genomes of eusocial hymenopteran
species are marked by exceptionally high rates of gene turnover (Simola et al. 2013a, Rappoport &
Linial 2015). Ant workers are either permanently or temporarily sterile, depending on the species.
The last common ancestor of all ants was clearly a queen-like reproductive, in the same way that the
last common ancestor of all cells in a tissue was a stem cell and not a somatic cell. Because queens
and workers share the same diploid genome, researchers thus hypothesize that the innovation of the
sterile worker caste of ants was related initially to temporal changes in expression of reproduction-
related genes (Linksvayer & Wade 2005) associated with cooperative brood care (Rehan & Toth
2015). The transition to distinct reproductive and sterile females appears to be related to changes
in conserved developmental networks involved in feeding, growth, and reproduction (Toth &
Robinson 2007, Chittka et al. 2012). This evolutionary process has involved novel genes, changes
in the coding sequences of existing genes, and developmental changes in gene regulation ( Johnson
& Tsutsui 2011, Jasper et al. 2014, Sumner 2014, Rehan & Toth 2015).
Genomic studies related to behavior in Hymenoptera have focused primarily on honey bees,
so the study of ant genetics draws heavily on tools developed in honey bee research. Honey bee
genetics drew initially on the genetic tools and databases of the vinegar fly, Drosophila melanogaster
(functional genomic resources reviewed in Mohr et al. 2014). Because honey bees have been under
artificial selection by humans for more than 10,000 years, the genetics of honey bee behavior may
not reflect the outcome of the diverse paths that evolution has taken in shaping ant behavior.
The study of molecular variation among ant species (reviewed in Nygaard & Wurm 2015)
began with the first ant genome sequence, published in 2010 (Bonasio et al. 2010), and was
followed quickly by many more publicly accessible genome sequences. The first seven species
whose genomes were published were Harpegnathos saltator, Camponotus floridanus, Acromyrmex
echinatior, Linepithema humile, Pogonomyrmex barbatus, Atta cephalotes, and Solenopsis invicta (Bonasio
et al. 2010, Nygaard et al. 2011, C.D. Smith et al. 2011, C.R. Smith et al. 2011, Suen et al. 2011,
Wurm et al. 2011). These were followed quickly by others, and there are now at least 24 ant
species with publicly accessible genomes, transcriptomes, or both (http://www.antgenomes.org,
accessed Jan. 21, 2015).
The seven ant species whose genomes were published initially all share a common ancestor from
approximately 90 million years ago and have been analyzed in the context of a large, 18-species,
arthropod phylogeny with a common ancestor from about 510 million years ago (Rappoport &
Linial 2015). Roux et al. (2014) found that ants show relaxed selection on immunity genes and
increased selection on neurogenesis- and olfactory-related genes. These changes may be due to
the importance of social processes related to immunity (Meunier 2015).
Ants rely on olfactory cues to gather information about their environment and to communicate,
and they have large and complex gene repertoires involved in lipid synthesis and olfaction. Com-
parisons of ant genomes show strong evolutionary change in the content of genes associated with
cuticular hydrocarbons (CHCs), oily glandular secretions that are used in nestmate recognition
(Tsutsui 2013); microbiome regulation; and desiccation resistance (Howard & Blomquist 2005).
Over the course of the diversification of ants, the gene families associated with CHC synthesis, in-
cluding desaturases, elongases, and fatty acid synthases (e.g., Badouin et al. 2013, McKenzie et al.
2014, Helmkampf et al. 2014 on desaturases), have expanded. CHCs and other environmental
semiochemicals (Vander Meer 2012) are perceived by binding to chemoreceptors, classified into
categories of odorant receptors, gustatory receptors, and ionotropic receptors (Tsutsui 2013). Sev-
eral studies have found evidence of selection acting on chemosensory gene families and patterns
of tissue-specific expression in transcriptomic data (Zhou et al. 2012, Koch et al. 2013, Kulmuni
et al. 2013, McKenzie et al. 2014, Zhou et al. 2015).
www.annualreviews.org • Ant Genetics
43
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 4

NE39CH03-Gordon
ARI
25 March 2016
13:12
cis-Regulatory
element: Noncoding
DNA region
influencing the level,
timing, or amount of
RNA expression of a
nearby or distant gene
Some olfactory perception genes have conserved sex- or tissue-specific roles, whereas others are
more labile. Ant species differ in their expression of homologous chemosensory genes, presumably
reflecting ecological differences in the odors they detect. Zhou et al. (2012) used RNA sequencing
(RNA-seq) to examine the expressed chemosensory repertoire in the antennae and bodies of
C. floridanus and H. saltator and found that some chemosensory genes displayed consistent sexually
dimorphic expression within these species; others had no sexual dimorphism or appeared to switch
the direction of overexpression between species. McKenzie et al. (2014) used RNA-seq on the
antennae and bodies of the raider ant Cerapachys biroi, C. floridanus, and H. saltator and found
interspecies differences in expression of the chemosensory repertoire, as well as one conserved,
antennal-specific chemoreceptor.
Ants show remarkable diversity in morphological and sexual phenotypes (Chittka et al. 2012),
radically diverged from their solitary, wasp-like ancestor (Ward 2014). This evolutionary process
has left significant, genome-wide patterns in gene content, gene order along the chromosome, and
cis–regulatory element composition, showing strong conservation of some noncoding regulatory
elements, enriched near genes with a role in nervous system regulation (Simola et al. 2013a). A
comparison of the genome sequences of four ant species (A. echinatior, S. invicta, C. floridanus, and
H. saltator) found that they all share the same set of neuropeptide genes (Nygaard et al. 2011), and
they share the loss of a RYamide receptor that is present in all other arthropod genomes (Caers
et al. 2012).
Ant species also differ in changes, associated with developmental stage, in the expression of
genes related to neurological differentiation and sensory perception. Ometto et al. (2011) com-
pared the whole-body transcriptome of larval and adult males, gynes (unmated reproductive
females), and workers in S. invicta and Solenopsis richteri and found the most interspecies tran-
scriptomic differences in adult workers they also observed that developmental stage influenced
transcriptome content more than species identity or sex. Analysis of small RNAs in C. floridanus
and H. saltator revealed that the downstream targets of small regulatory RNAs are enriched for pro-
cesses of neuron differentiation, neurogenesis, and steroid signaling (Bonasio et al. 2010, Simola
et al. 2013a).
MALES AND FEMALES
Genetic studies show transcriptomic differences between male and female ants (Nipitwattanaphon
et al. 2014 in S. invicta). Females, both reproductive gynes and sterile workers, are more similar to
each other than to males (Ometto et al. 2011). This may be explained partially by genome ploidy:
Female ants are diploid, and males are haploid. Haploidy at the complementary sex-determination
locus in honey bees causes male development (Beye et al. 2003), although it is not clear if all ant
species use the same mechanism of sex determination. Reanalysis of the data sets of Bonasio et al.
(2010, 2012) showed a strong, sexually dimorphic link between DNA methylation and histone
posttranslational modifications in C. floridanus (Glastad et al. 2015). Zhou et al. (2012) found that
males and females differ in the expression of chemosensory proteins in the antennae of C. floridanus
and H. saltator. Male ants are very short-lived and do not participate in the activities of the workers.
Little is known about their behavior (reviewed in Beani et al. 2014).
REPRODUCTIVE AND STERILE FEMALES
Studies comparing reproductive and worker females have focused on genes such as vitellogenin (Vg)
associated with reproductive physiology in other insects (reviewed in Heinze & Schrempf 2008,
Libbrecht et al. 2013). Reproductive female ants tend to perform few tasks other than laying eggs,
44
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 5

NE39CH03-Gordon
ARI
25 March 2016
13:12
Gene ontology
(GO):
Controlled-vocabulary
system that describes
the biological
function, relevant
processes, and cellular
localization associated
with a given gene
RNA editing: Process
by which mRNA
nucleotide molecules
are modified
enzymatically, leading
to an mRNA with
information that
differs from the
genome
so most genetic studies of the differences between reproductive and sterile females investigate
reproductive physiology rather than behavior. The first seven published ant genomes all contain
three Vg-like genes in addition to Vg, although there are also a few lineage-specific duplications and
deletions (Morandin et al. 2014). Gene expression analyses of the four Vg family genes across seven
Formica species showed consistent worker-specific expression of Vg-like-C, but expression levels at
the other paralogous loci did not display a consistent direction of expression bias between queens
and workers (Morandin et al. 2014). Oxley et al. (2014) found that in the cyclically reproductive
raider ant C. biroi, the head and abdomen expression of the Vg paralog Vgq was upregulated during
the reproductive phase of the lifecycle, whereas another (Vgw) was upregulated during the brood
care phase. This is the opposite trend from that found by Corona et al. (2013), who used reverse
transcription quantitative polymerase chain reaction (rt-qPCR) to compare expression of Vg genes
in laboratory colonies of P. barbatus. They quantified gene expression in queens, nurses (defined
as “young ants interacting with the brood in the nest tube”) and foragers (defined as “any ant
handling a food item in the foraging area”) (Corona et al. 2013, p. 7). They found that some Vg
family members are upregulated in foragers, whereas others are upregulated in queens and nurses,
a pattern also observed by Feldmeyer et al. (2014) in Temnothorax.
Several transcriptomic studies have demonstrated that there are few gene expression differences
between reproductive and sterile females. Morandin et al. (2015) used RNA-seq on whole bodies
of the adult and pupal stages of Formica exsecta queens and workers and found that the samples
clustered more by developmental stage than by reproductive status. Genes differentially expressed
between queens and workers were not enriched consistently across developmental time points
for any functional annotations, although each stage-specific comparison displayed enrichment
in several gene ontology (GO) categories. Transcriptomic comparisons of queens and workers
showed few differences for Pogonomyrmex and Vollenhovia host/parasite species dyads (Smith et al.
2015). Ometto et al. (2011) showed that the whole-body transcriptome of S. invicta workers is
closer to that of queens than that of males.
Other studies have indicated interesting expression differences between reproductive and sterile
females. Li et al. (2014) found differences between gynes and workers in transcriptomic patterns of
RNA editing in heads from the leaf-cutter ant A. echinatior. Differentially edited transcripts came
from genomic loci that were enriched in GO categories relevant to neurotransmission, circadian
rhythm, and carboxylic acid biosynthesis. They also found A-to-I RNA editing sites that differ
between gynes and workers, including in the genes TBPH and wah, which have been implicated
in locomotor behavior in D. melanogaster (Li et al. 2014). Feldmeyer et al. (2014), using RNA-
seq on pooled whole-bodies of queens, foragers, fertile brood-carers, and sterile brood-carers in
Temnothorax longispinosus, found that genes that were differentially expressed between queens and
workers tended to be poorly annotated and had low overlap with genes identified in other species.
This suggests that genes differentially expressed between reproductive and sterile females tend to
be of recent evolutionary origin and hence cannot be annotated from the honey bee (Apis mellifera)
or D. melanogaster genomes. This supports the idea, predicted by Linksvayer & Wade (2005), that
rapid evolution is occurring in genes associated with workers (see Johnson & Tsutsui 2011 and
Sumner 2014 for theoretical perspectives; for experimental studies, see Harpur et al. 2014 on
honey bees and Ferreira et al. 2013 on wasps).
Other studies comparing female reproductives and sterile workers investigate the remarkable
longevity of female reproductives relative to workers. Using whole-body transcriptomes, Bonasio
et al. (2010) found that relative to workers, long-lived H. saltator reproductives had upregulation
of genes known to play a role in longevity in other species, including humans (e.g. genes encoding
telomeraseand sirtuin deacetylase).In both H. saltator and C. floridanus, the expression of epigenetic
regulators such as miRNAs and histone methyltransferases, as well as those related to neuronal
www.annualreviews.org • Ant Genetics
45
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 6

NE39CH03-Gordon
ARI
25 March 2016
13:12
function and chemical communication, was associated with reproductive status. Highly methylated
genes tended to be expressed at medium levels in eggs, larvae, males, gamergates (reproductively
active worker ants), and workers of C. floridanus and H. saltator (Bonasio et al. 2012), as in the
honey bee (Foret et al. 2009). Both species showed the same pattern between queens and workers
of differential methylation of genes associated with reproductive biology, telomere maintenance,
and noncoding RNA metabolism. However, a recent study of the relationship between DNA
methylation and reproductive status in C. biroi found no genes that were differentially methylated
between ants in the worker-like or queen-like phases (Libbrecht et al. 2016). Their comparison
of statistical techniques suggests that other results showing such differences may be misleading,
owing to insufficient sample size.
In some ant species, there seems to be a genetic association with the development of queens
or sterile workers. Early microsatellite studies showed that some populations of harvester ants
in the genus Pogonomyrmex have two dependent interbreeding lineages. Females are diploid and
produced by a mated queen; her matings within a mitochondrial lineage produce reproductive
females, whereas matings between mitochondrial lineages produce workers (Volny & Gordon
2002, Helms Cahan & Keller 2003). Evidence is mixed about the possibility of a hybrid origin of
these systems (Anderson et al. 2006, Schwander et al. 2007, Sirvi¨o et al. 2011, Smith et al. 2012);
further genetic studies are needed to resolve this (Mott et al. 2015). Eggs are laid in the ratio
of the queen’s mates, but reproductive eggs are consumed by workers in young colonies (Clark
et al. 2006), and reproductives are produced when a colony is about five years old (Gordon 1995).
Thus, a female’s reproductive status depends not only on the genetic lineage of her parents but
also on the behavior of the workers (Linksvayer et al. 2006, Volny et al. 2006). The population
ratio of the two lineages tends to be asymmetric. For example, a long-term study of a dependent-
lineage population of P. barbatus shows that the asymmetric lineage ratio has persisted for more
than 20 years (Gordon et al. 2013), and there was no evidence of any behavioral or ecological
differences between the lineages in foraging activity, nest size, or other measures, suggesting that
the asymmetric ratio must be maintained by sex ratio differences (Gordon et al. 2013).
QUEEN NUMBER
The first investigation of a link between ant behavior and genetics examined the processes that
determine the number of reproductives or queens in colonies of the fire ant S. invicta. In some ant
species, colonies are monogynous, with a single queen, whereas others are polygynous, with more
than one queen per colony. In some species, such as S. invicta, colonies can be either monogynous or
polygynous (Fletcher et al. 1980). Electrophoretic gel surveys of allozyme diversity in a population
of S. invicta revealed that the genotype at a single locus encoding the enzyme phosphoglucomutase
3(Pgm-3), was associated with queen number (Ross 1992). All combinations of the two alleles at
the Pgm-3 locus (a and b) were observed in queens in monogynous colonies (aa, ab, bb), whereas
polygynous queens were never of the aa genotype. A nearby polymorphic genetic element was
determined to be a better predictor of colony queen number, marked by two alleles (B and b)
at the general protein 9 (Gp-9) locus (Keller & Ross 1999). In polygynous colonies, daughter
gynes are sometimes recruited as new queens (DeHeer et al. 1999). Queens of the BB genotype
introduced to existing colonies were rejected and ultimately killed by workers (Keller & Ross
1998). Monogynous colonies of S. invicta are often founded with multiple queens, which then
fight amongst each other until only one queen remains, a system called pleometrosis. Whole-body
transcriptomic differences between winner and loser queens include 43 genes in GO categories
related to the metabolism of lipids and hormones (Manfredini et al. 2013). The Gp-9 protein is a
46
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 7

NE39CH03-Gordon
ARI
25 March 2016
13:12
Indirect genetic
effects: Components
of phenotypic variance
attributable to the
genotype of another,
usually conspecific,
individual
putative member of the odorant binding protein family, which suggests that odor may be related
to aggressive interactions between workers and queens (reviewed in Krieger 2005).
Subsequent work showed that many genes are associated with queen number in S. invicta.
Wang et al. (2008) performed whole-body transcriptomes of BB and Bb workers from polygynous
colonies using a custom cDNA microarray and showed a significant role for indirect genetic
effects (reviewed in Linksvayer 2015). There were 39 genes differentially expressed between the
two genotypes of workers in polygynous colonies and 91 genes differentially expressed in BB
workers from monogynous versus polygynous colonies (Wang et al. 2008). Wang et al. (2013)
then found that the association of Gp-9 genotype with queen number was due to a large (13-Mb),
nonrecombining genomic inversion that includes the Gp-9 locus and 615 other genes of mainly
unknown function. The inversion is enriched for the genes that were differentially expressed in
the study by Wang et al. (2008). Recent work suggests that this inversion may alter the chemical
scent of an ant carrying it, as well as altering the response of that ant to others (Trible & Ross
2015).
Queen number is also associated with a genomic inversion in the Alpine silver ant, Formica selysi,
in which some populations also contain both monogynous and polygynous colonies (reviewed in
Rosset & Chapuisat 2006). Queen number is a labile trait at the colony level in F. selysi (Purcell
& Chapuisat 2013). Purcell et al. (2014), using linkage mapping and genome sequencing, found
that a large genomic inversion with suppressed recombination segregates between the two forms
and contains hundreds of genes. No homology was observed between the genomic inversions of
S. invicta and F. selysi.
WORKER BODY SIZE
The body size of workers is associated with differences in gene expression and DNA methylation.
About 15% of ant genera have adult workers showing marked differences in size within a colony
(Oster & Wilson 1978, Gouws et al. 2011). The larger workers are sometimes called majors and the
smaller ones minors. Evidence suggests flexibility of task, rather than specialization according to
body size (Wilson 1984, Patel 1990, Brown & Traniello 1998, Sempo & Detrain 2004). Differences
among workers in size do not necessarily reflect differences in behavior.
Several studies show distinctive patterns of gene expression in major and minor workers of
C. floridanus. Major and minor C. floridanus do not differ in their CHC profile or in their observed
frequency of resting behavior (Endler et al. 2007). Simola et al. (2013b) examined differences in
histone modifications and whole-body gene expression in males, majors, and minors of C. floridanus
and found that majors and minors differed in the patterns of several histone modifications across
18% of the genome, linked with loci that had been associated previously with reproductive status
in honey bees (Spannhoff et al. 2011) and with learning and memory in mice (Peleg et al. 2010).
These differences in histone modifications were associated with RNA expression changes in genes
enriched for GO terms related to, for example, muscle development, which was enriched in majors,
and synaptic transmission, which was enriched in minors.
A recent study of C. floridanus indicates that differences in the activity of large and small
workers may be due to differences in sensitivity to stimuli, mediated by changes in the regulation
of sensitivity-modulating genes (Simola et al. 2016). The long-term stability associated with these
epigenetic transformations is reminiscent of the cell-type model of ant phenotypic differentiation
(figure 2 in Chittka et al. 2012). Other studies show epigenetic differences related to body size in
C. floridanus. Alvarado et al. (2015) found that the epidermal growth factor receptor (Egfr) locus
was hypermethylated and downregulated in larger workers. Egfr also plays a role in establishing
www.annualreviews.org • Ant Genetics
47
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 8

NE39CH03-Gordon
ARI
25 March 2016
13:12
size polyphenism in A. mellifera (Kamakura 2011). Taken together, the work of Alvarado et al.
(2015) and Simola et al. (2016) has demonstrated experimental epigenetic control over the
intermorphological differences in body size and activity in C. floridanus.
BEHAVIOR
Heritability of Task Performance
Genetic markers reveal parental effects on worker morphology and behavior. Using mitochondrial
and microsatellite markers to determine matrilines and patrilines, studies of laboratory colonies
of Temnothorax ants partitioned morphological variation into components of species, individual
genotype, genotype of nestmates, and maternal environment (Linksvayer 2006 in Temnothorax
curvispinosus, Linksvayer 2007 in three species of Temnothorax ants), revealing a role for each in
phenotypic variability.
Many studies suggest heritability of behavioral variation from parent reproductive to workers
within a colony, and from parent reproductive to the offspring reproductives that found new
colonies. For example, wild colonies of P. barbatus resemble their mothers with regard to the
regulation of foraging in poor conditions (Gordon 2013, Ingram et al. 2013). Patrilines of wild
Formica argentea colonies displayed biases in their frequency of nest patrolling, nest maintenance,
and queen guarding(Snyder 1992). Wiernasz et al. (2008) found that wild colonies ofPogonomyrmex
occidentalis founded by queens with more mates (observed range: 3–10) tended to begin foraging
earlier in the morning and foraged for longer during the day.
Quantitative genetic studies show heritable differences in task performance. In laboratory
colonies of Pogonomyrmex californicus, workers of different matrilines differed in task performance,
with a consistent trade-off between brood care and waste management (Holbrook et al. 2013).
Workers in laboratory colonies of F. argentea had an allozyme polymorphism that was associated
with patterns of nestmate grooming and leaving the nest but not with worker-queen interactions
(Snyder 1993). In composite laboratory colonies of Acromyrmex versicolor, workers from different
matrilines differed in task performance and in the age of initiation of foraging ( Julian & Fewell
2004). In composite laboratory colonies of Leptothorax rudis, workers from different wild colonies
demonstrated a bias in the frequency of foraging (Stuart & Page 1991).
Worker Behavior in the Absence of a Queen
Whether workers are in contact with a queen affects both behavior and gene expression (Feldmeyer
et al. 2014 and references therein). Manfredini et al. (2014) compared the whole-body transcrip-
tomes of workers collected from inside the nest box or out in a foraging area of laboratory colonies
of S. invicta and found several hundred genes to be differentially expressed. Sampling location ex-
plained 57% of the variance in gene expression, and differentially expressed genes were enriched
in GO terms related to musculature and energetic metabolism. Differentially expressed genes
between inside and outside workers of S. invicta were not the same as those reported previously in
honey bees and in the wasp Polistes metricus. When a colony fragment had been separated from the
queen, more reproductive larvae were allowed to survive, and conspecific aggression decreased.
In the queenless fragments, the transcriptomic differences between inside and outside workers
disappeared. This suggests that behavior related to reproduction and aggression is associated with
ongoing shifts in gene expression. The behavior associated with worker treatment of reproductive
larvae provides an opportunity to investigate these interactions.
48
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 9

NE39CH03-Gordon
ARI
25 March 2016
13:12
Age-Related Changes in Gene Expression
Ants tend to move through a series of tasks as they grow older, from work inside the nest to outside
(Gordon 2015), and recent work shows that this is associated with changes in gene expression.
Younger ants working inside the nest, for example, caring for the eggs, larvae, and pupae, differ
in gene expression from older ants working outside the nest, for example, foraging for resources.
Mikheyev & Linksvayer (2015) used whole-body RNA-seq to investigate gene expression associ-
ated with differences in worker behavior in laboratory colonies of Monomorium pharaonis. Nurse
ants interacted with brood in the nest. At the age of 9–12 days, ants tended to become foragers,
defined as those observed on a food or water source, or carrying food. Nurse-upregulated genes
were enriched for GO categories related to metabolism and chromatin modifications. Compared
to nurse-upregulated genes, forager-upregulated genes tended to be more connected in gene reg-
ulatory networks and had higher levels of evolutionary conservation. A similar trend is observed in
honey bees, in which genes with low network connectedness have higher rates of coding sequence
change, which, along with lineage-specific genes, is hypothesized to play a role in phenotypic
diversification ( Jasper et al. 2014). Age-related changes in behavior in workers, known as age
polyethism, are widespread in social insects (Gordon 2015, Rehan & Toth 2015), and these recent
studies have begun to provide insight into the molecular mechanisms associated with ontogenetic
changes in behavior.
Circadian Rhythms and the Foraging Gene
The expression of genes involved in circadian rhythms is associated with temporal patterns of
worker activity. Ingram et al. (2012) examined gene expression in laboratory colonies of S. invicta
and found that eight genes involved in circadian rhythms had oscillatory dynamics throughout
the day, similar to those observed in A. mellifera (Ingram et al. 2012), and resembled mammalian
patterns more than those of D. melanogaster (Tataroglu & Emery 2014). De Bekker et al. (2015)
analyzedthetranscriptomesofCamponotus castaneusworkersduringaninfectionwithOphiocordyceps
unilateralis sensu lato, a fungal parasite that induces a fatal sequence of ant behavior at a certain
time of the day. RNA-seq on the brains of infected ants revealed alterations in circadian gene
oscillation, biogenic amine signaling, and immune response.
The foraging gene ( foraging) is associated with activity in many species, and has been studied
in ants, with diverse results. Sokolowski (1980) first studied this gene in D. melanogaster. Rover
larvae move around more than sitters in both laboratory and wild populations, and this difference
persists into adulthood (Sokolowski & Bauer 1989). Molecular analysis identified the foraging gene
as a cyclic guanosine monophosphate (cGMP)–dependent protein kinase (PKG) (Osborne et al.
1997), and associations between movement and PKG enzymatic activity have been demonstrated
in many species (reviewed in Kaun & Sokolowski 2009). Honey bee forager heads show multifold
higher expression of foraging (known as Amfor in this species) relative to nurses. Brain PKG activity
measured higher in foragers, as quantified with an in vitro enzyme assay. Treatment with 8Br-
cGMP, which elevates PKG activity, induced precocious foraging (Ben-Shahar et al. 2002). In
situ RNA hybridization of Amfor in the honey bee brain showed gene expression in the lamina
of the optic lobes and the mushroom bodies (Ben-Shahar et al. 2002), suggesting that increased
expression of Amfor may induce maturation and foraging behavior via an increase in positive
phototaxis (Ben-Shahar 2003).
Patterns of expression of the foraging gene in ants differ from those found in honey bees.
Lucas & Sokolowski (2009) compared foraging enzymatic activity in major and minor workers in
Pheidole pallidula (Wilson 1984, Patel 1990, Brown & Traniello 1998, Sempo & Detrain 2004).
Major worker brains had more PKG enzymatic activity, and one isoform of for showed protein
www.annualreviews.org • Ant Genetics
49
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 10

NE39CH03-Gordon
ARI
25 March 2016
13:12
expression in more neurons. When increased PKG activity in vivo was induced with 8Br-cGMP,
both sizes of workers were less likely to interact with a foraging stimulus (a live mealworm), and
majors, but not minors, were more likely to respond to a defense stimulus (the introduction of
200 minor and 25 major workers from another nest of P. pallidula). Untreated majors were more
likely to forage and equally as aggressive as untreated minor workers.
The expression of the foraging gene is related to circadian rhythms. Using rt-qPCR, Ingram
et al. (2005) found in both laboratory and field colonies of P. barbatus that foraging, traveling
outside the nest to search for food, is associated with lower expression of PbFor than work inside
the nest. This pattern is similar to the ant species S. invicta (Lucas et al. 2015) and C. biroi (Oxley
et al. 2014) and opposite that observed in D. melanogaster, A. mellifera, and Caenorhabditis elegans.
Expression levels of period, a known circadian gene, differed according to worker task in laboratory
colonies of P. occidentalis. Ingram et al. (2009) used rt-qPCR to show that P. occidentalis foragers,
defined as ants that touched food in the foraging area, have strong, seasonally influenced circadian
fluctuations in period expression, whereas interior nest workers, identified as ants that never entered
the foraging arena, are arrhythmic. Foragers, but not nest workers, from laboratory colonies of
P. barbatus showed circadian fluctuations in the level of foraging gene expression (Ingram et al.
2011). Foragers exhibit cyclic patterns of PbFor expression, peaking at midday, whereas interior
workers are arrhythmic.
CONCLUSIONS
The social organization of ant colonies arises from behavioral interactions among individuals.
Observational studies of behavior will be needed to examine the genetics of individual ant behav-
ior and determine how these combine to produce the collective behavior of ant colonies. Genetic
changes in physiological processes related to responses to interactions are likely to influence colony
behavior (e.g., Gordon 2014, Simola et al. 2016). For example, changes in neurophysiological pro-
cesses in ants influence social interactions and task performance (Kamhi & Traniello 2013, Katz &
Lillvis 2014). Transcriptomic analysis is identifying candidate genes, for example, in reproductive
physiology, that may have important effects on social interactions and thus on collective behavior.
To investigate ant behavior genetically, we will need to be aware of how different variables, such
as the developmental stage, sampled tissue, and time of day, affect results. For example, studies
across developmental time points have found interstage inconsistencies in patterns of differential
gene expression (e.g., Morandin et al. 2015, Smith et al. 2015). It will be important to extend
the notion of simple associations between genes and traits, as in GO annotations, to understand
the many relational genetic processes that contribute to development and behavior. In addition,
many studies use whole-body samples for transcriptomic studies, which may conceal tissue-specific
differences in variation or detect false positives between biological groups owing to tissue allometry
(discussed in Johnson et al. 2013). Brain- or at least head-specific gene expression studies in ants
are encouraging and have found applicable results (e.g., Zhou et al. 2012 on antennae, Li et al.
2014 on heads, de Bekker et al. 2015 and Simola et al. 2016 on brains). The time of day of tissue
sampling and behavioral testing can also radically alter results.
Future studies may be able to harness techniques such as RNA interference (RNAi) and
CRISPR (Barrangou et al. 2015) to examine the genetics of ant behavior. RNAi has now been
used in ants to examine reproductive physiology (Lu et al. 2009); immune response (Ratzka et al.
2013); and the development of sexually dimorphic pigmentation (Miyazaki et al. 2014), pheromone
biosynthesis (Choi et al. 2012), chemosensory protein function (Cheng et al. 2015), and worker
activity (Simola et al. 2016). The application of CRISPR to ants has not yet been published and
will be an exciting technological advance in ant genomics.
50
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 11

NE39CH03-Gordon
ARI
25 March 2016
13:12
The next step in the study of the genetics of ant behavior will be to learn about the feedback
between individual-level physiological changes and socially mediated responses to environmental
conditions. What genetic mechanisms regulate social interactions, and how do these produce
variation among colonies upon which natural selection can act? The answers to these questions
are likely to differ greatly among species. The enormous ecological diversity of ants has led to
great diversity in behavior. Studies of behavioral genetics are needed that investigate the interplay
of behavior and environment in the collective behavior of ant colonies.
DISCLOSURE STATEMENT
The authors are not aware of any affiliations, memberships, funding, or financial holdings that
might be perceived as affecting the objectivity of this review.
ACKNOWLEDGMENTS
We are grateful to Barbara Feldmeyer and Tim Linksvayer for helpful comments on the
manuscript.
LITERATURE CITED
Alvarado S, Rajakumar R, Abouheif E, Szyf M. 2015. Epigenetic variation in the Egfr gene generates quanti-
tative variation in a complex trait in ants. Nat. Commun. 6:6513
Anderson KE, Gadau J, Mott BM, Johnson RA, Altamirano A, et al. 2006. Distribution and evolution of
genetic caste determination in Pogonomyrmex seed-harvester ants. Ecology 87:2171–84
Badouin H, Belkhir K, Gregson E, Galindo J, Sundstr¨om L, et al. 2013. Transcriptome characterisation of
the ant Formica exsecta with new insights into the evolution of desaturase genes in social hymenoptera.
PLOS ONE 8:e68200
Barrangou R, Birmingham A, Wiemann S, Beijersbergen RL, Hornung V, van Brabant Smith A. 2015. Ad-
vances in CRISPR-Cas9 genome engineering: lessons learned from RNA interference. Nucleic Acids Res.
43:3407–19
Beani L, Dess`ı-Fulgheri F, Cappa F, Toth A. 2014. The trap of sex in social insects: from the female to the
male perspective. Neurosci. Biobehav. Rev. 46(Pt. 4):519–33
Ben-Shahar Y. 2003. cGMP-dependent changes in phototaxis: a possible role for the foraging gene in honey
bee division of labor. J. Exp. Biol. 206:2507–15
Ben-Shahar Y, Robichon A, Sokolowski MB, Robinson GE. 2002. Influence of gene action across different
time scales on behavior. Science 296:741–44
Beye M, Hasselmann M, Fondrk MK, Page RE Jr., Omholt SW. 2003. The gene csd is the primary signal for
sexual development in the honeybee and encodes an SR-type protein. Cell 114:419–29
Bonasio R, Li Q, Lian J, Mutti NS, Jin L, et al. 2012. Genome-wide and caste-specific DNA methylomes of
the ants Camponotus floridanus and Harpegnathos saltator. Curr. Biol. 22:1755–64
Bonasio R, Zhang G, Ye C, Mutti NS, Fang X, et al. 2010. Genomic comparison of the ants Camponotus
floridanus and Harpegnathos saltator. Science 329:1068–71
Brown JJ, Traniello JFA. 1998. Regulation of brood-care behavior in the dimorphic castes of the ant Pheidole
morrisi (Hymenoptera: Formicidae): effects of caste ratio, colony size, and colony needs. J. Insect Behav.
11:209–19
Caers J, Verlinden H, Zels S, Vandersmissen HP, Vuerinckx K, Schoofs L. 2012. More than two decades of
research on insect neuropeptide GPCRs: an overview. Front. Endocrinol. 3:151
Cheng D, Lu Y, Zeng L, Liang G, He X. 2015. Si-CSP9 regulates the integument and moulting process of
larvae in the red imported fire ant, Solenopsis invicta. Sci. Rep. 5:9245
Chittka A, Wurm Y, Chittka L. 2012. Epigenetics: the making of ant castes. Curr. Biol. 22:835–38
www.annualreviews.org • Ant Genetics
51
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 12

NE39CH03-Gordon
ARI
25 March 2016
13:12
Choi M-Y, Vander Meer RK, Coy M, Scharf ME. 2012. Phenotypic impacts of PBAN RNA interference in
an ant, Solenopsis invicta, and a moth, Helicoverpa zea. J. Insect Physiol. 58:1159–65
Clark RM, Anderson KE, Gadau J, Fewell JH. 2006. Behavioral regulation of genetic caste determination in
a Pogonomyrmex population with dependent lineages. Ecology 87:2201–6
Corona M, Libbrecht R, Wurm Y, Riba-Grognuz O, Studer RA, Keller L. 2013. Vitellogenin underwent
subfunctionalization to acquire caste and behavioral specific expression in the harvester ant Pogonomyrmex
barbatus. PLOS Genet. 9:e1003730
de Bekker C, Ohm RA, Loreto RG, Sebastian A, Albert I, et al. 2015. Gene expression during zombie ant
biting behavior reflects the complexity underlying fungal parasitic behavioral manipulation. BMC Genom.
16:620
DeHeer CJ, Goodisman MAD, Ross KG. 1999. Queen dispersal strategies in the multiple-queen form of the
fire ant Solenopsis invicta. Am. Nat. 153:660–75
Endler A, H¨olldobler B, Liebig J. 2007. Lack of physical policing and fertility cues in egg-laying workers of
the ant Camponotus floridanus. Anim. Behav. 74:1171–80
Feldmeyer B, Elsner D, Foitzik S. 2014. Gene expression patterns associated with caste and reproductive status
in ants: worker-specific genes are more derived than queen-specific ones. Mol. Ecol. 23:151–61
Ferreira PG, Patalano S, Chauhan R, Ffrench-Constant R, Gabald´on T, et al. 2013. Transcriptome analyses of
primitively eusocial wasps reveal novel insights into the evolution of sociality and the origin of alternative
phenotypes. Genome Biol. 14:R20
Fletcher DJC, Blum MS, Whitt TV, Temple N. 1980. Monogyny and polygyny in the fire ant, Solenopsis
invicta. Ann. Entomol. Soc. Am. 73:658–61
Foret S, Kucharski R, Pittelkow Y, Lockett GA, Maleszka R. 2009. Epigenetic regulation of the honey bee
transcriptome: unravelling the nature of methylated genes. BMC Genom. 10:472
Gadau J, Helmkampf M, Nygaard S, Roux J, Simola DF, et al. 2012. The genomic impact of 100 million years
of social evolution in seven ant species. Trends Genet. 28:14–21
Glastad KM, Chau LM, Goodisman MAD. 2015. Chapter seven – epigenetics in social insects. In Advances
in Insect Physiology: Genomics, Physiology and Behaviour of Social Insects, Vol. 48, ed. A Zayed, CF Kent,
pp. 227–69. London: Academic
Gordon DM. 1995. The development of an ant colony’s foraging range. Anim. Behav. 49:649–59
Gordon DM. 2013. The rewards of restraint in the collective regulation of foraging by harvester ant colonies.
Nature 498:91–93
Gordon DM. 2014. The ecology of collective behavior. PLOS Biol. 12(3):e1001805
Gordon DM. 2015. From division of labor to the collective behavior of social insects. Behav. Ecol. Sociobiol. In
press. doi: 10.1007/s00265-015-2045-3
Gordon DM, Pilko A, De Bortoli N, Ingram KK. 2013. Does an ecological advantage produce the asymmetric
lineage ratio in a harvester ant population? Oecologia 173:849–57
Gouws EJ, Gaston KJ, Chown SL. 2011. Intraspecific body size frequency distributions of insects. PLOS ONE
6:e16606
Harpur BA, Kent CF, Molodtsova D, Lebon JMD, Alqarni AS. 2014. Population genomics of the honey bee
reveals strong signatures of positive selection on worker traits. PNAS 111(7):2614–19
Heinze J, Schrempf A. 2008. Aging and reproduction in social insects – a mini-review. Gerontology 54:160–67
Helmkampf M, Cash E, Gadau J. 2014. Evolution of the insect desaturase gene family with an emphasis on
social hymenoptera. Mol. Biol. Evol. 32(2):456–71
Helms Cahan S, Keller L. 2003. Complex hybrid origin of genetic caste determination in harvester ants.
Nature 424:306–9
Holbrook CT, Eriksson TH, Overson RP, Gadau J, Fewell JH. 2013. Colony-size effects on task organization
in the harvester ant Pogonomyrmex californicus. Insectes Sociaux 60:191–201
Howard RW, Blomquist GJ. 2005. Ecological, behavioral, and biochemical aspects of insect hydrocarbons.
Annu. Rev. Entomol. 50:371–93
Ingram KK, Kleeman L, Peteru S. 2011. Differential regulation of the foraging gene associated with task
behaviors in harvester ants. BMC Ecol. 11:19
Ingram KK, Krummey S, LeRoux M. 2009. Expression patterns of a circadian clock gene are associated with
age-related polyethism in harvester ants, Pogonomyrmex occidentalis. BMC Ecol. 9:7
52
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 13

NE39CH03-Gordon
ARI
25 March 2016
13:12
Ingram KK, Kutowoi A, Wurm Y, Shoemaker D, Meier R, Bloch G. 2012. The molecular clockwork of the
fire ant Solenopsis invicta. PLOS ONE 7:e45715
Ingram KK, Oefner P, Gordon DM. 2005. Task-specific expression of the foraging gene in harvester ants.
Mol. Ecol. 14:813–18
Ingram KK, Pilko A, Heer J, Gordon DM. 2013. Colony life history and lifetime reproductive success of red
harvester ant colonies. J. Anim. Ecol. 82:540–50
Jasper WC, Linksvayer TA, Atallah J, Friedman DA, Chiu JC, Johnson BR. 2014. Large-scale coding sequence
change underlies the evolution of postdevelopmental novelty in honey bees. Mol. Biol. Evol. 32(2):334–46
Johnson BR, Borowiec ML, Chiu JC, Lee EK, Atallah J, Ward PS. 2013. Phylogenomics resolves evolutionary
relationships among ants, bees, and wasps. Curr. Biol. 23:2058–62
Johnson BR, Linksvayer TA. 2010. Deconstructing the superorganism: social physiology, groundplans, and
sociogenomics. Q. Rev. Biol. 85:57–79
Johnson BR, Tsutsui ND. 2011. Taxonomically restricted genes are associated with the evolution of sociality
in the honey bee. BMC Genom. 12:164
Julian GE, Fewell JH. 2004. Genetic variation and task specialization in the desert leaf-cutter ant, Acromyrmex
versicolor. Anim. Behav. 68:1–8
Kamakura M. 2011. Royalactin induces queen differentiation in honeybees. Nature 473:478–83
Kamhi JF, Traniello JFA. 2013. Biogenic amines and collective organization in a superorganism: neuromod-
ulation of social behavior in ants. Brain Behav. Evol. 82:220–36
Katz PS, Lillvis JL. 2014. Reconciling the deep homology of neuromodulation with the evolution of behavior.
Curr. Opin. Neurobiol. 29:39–47
Kaun KR, Sokolowski MB. 2009. cGMP-dependent protein kinase: linking foraging to energy homeostasis.
Genome 52:1–7
Keller L, Ross KG. 1998. Selfish genes: a green beard in the red fire ant. Nature 394:573–75
Keller L, Ross KG. 1999. Major gene effects on phenotype and fitness: the relative roles of Pgm-3 and Gp-9
in introduced populations of the fire ant Solenopsis invicta. J. Evol. Biol. 12:672–80
Koch SI, Groh K, Vogel H, Hansson BS, Hannson BS, et al. 2013. Caste-specific expression patterns of
immune response and chemosensory related genes in the leaf-cutting ant, Atta vollenweideri. PLOS ONE
8:e81518
Krieger MJB. 2005. To b or not to b: a pheromone-binding protein regulates colony social organization in
fire ants. Bioessays 27:91–99
Kulmuni J, Wurm Y, Pamilo P. 2013. Comparative genomics of chemosensory protein genes reveals rapid
evolution and positive selection in ant-specific duplicates. Heredity 110:538–47
Li Q, Wang Z, Lian J, Schiott M, Jin L, et al. 2014. Caste-specific RNA editomes in the leaf-cutting ant
Acromyrmex echinatior. Nat. Commun. 5:4943
Libbrecht R, Oxley PR, Keller L, Kronauer DJC. 2016. Robust DNA methylation in the clonal raider ant
brain. Curr. Biol. 26:391–95
Libbrecht R, Oxley PR, Kronauer DJC, Keller L. 2013. Ant genomics sheds light on the molecular regulation
of social organization. Genome Biol. 14:212
Linksvayer TA. 2006. Direct, maternal, and sibsocial genetic effects on individual and colony traits in an ant.
Evolution 60:2552–61
Linksvayer TA. 2007. Ant species differences determined by epistasis between brood and worker genomes.
PLOS ONE 2:e994
Linksvayer TA. 2015. The molecular and evolutionary genetic implications of being truly social for the social
insects. Adv. Insect Physiol. 48:271–92
Linksvayer TA, Fewell JH, Gadau J, Laubichler MD. 2012. Developmental evolution in social insects: regu-
latory networks from genes to societies. J. Exp. Zool. Part B: Mol. Dev. Evol. 318:159–69
Linksvayer TA, Wade MJ. 2005. The evolutionary origin and elaboration of sociality in the aculeate Hy-
menoptera: maternal effects, sib-social effects, and heterochrony. Q. Rev. Biol. 80:317–36
Linksvayer TA, Wade MJ, Gordon DM. 2006. Genetic caste determination in harvester ants: possible origin
and maintenance by cyto-nuclear epistasis. Ecology 87:2185–93
www.annualreviews.org • Ant Genetics
53
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 14

NE39CH03-Gordon
ARI
25 March 2016
13:12
Lu H-L, Vinson SB, Pietrantonio PV. 2009. Oocyte membrane localization of vitellogenin receptor coincides
with queen flying age, and receptor silencing by RNAi disrupts egg formation in fire ant virgin queens.
FEBS J. 276:3110–23
Lucas C, Nicolas M, Keller L. 2015. Expression of foraging and Gp-9 are associated with social organization
in the fire ant Solenopsis invicta. Insect Mol. Biol. 24:93–104
Lucas C, Sokolowski MB. 2009. Molecular basis for changes in behavioral state in ant social behaviors. PNAS
106:6351–56
Manfredini F, Lucas C, Nicolas M, Keller L, Shoemaker D, Grozinger CM. 2014. Molecular and social
regulation of worker division of labour in fire ants. Mol. Ecol. 23:660–72
Manfredini F, Riba-Grognuz O, Wurm Y, Keller L, Shoemaker D, Grozinger CM. 2013. Sociogenomics of
cooperation and conflict during colony founding in the fire ant Solenopsis invicta. PLOS Genet. 9:e1003633
McKenzie SK, Oxley PR, Kronauer DJC. 2014. Comparative genomics and transcriptomics in ants provide
new insights into the evolution and function of odorant binding and chemosensory proteins. BMC Genom.
15:718
Meunier J. 2015. Social immunity and the evolution of group living in insects. Philos. Trans. R. Soc. B
370:20140102
Mikheyev AS, Linksvayer TA. 2015. Genes associated with ant social behavior show distinct transcriptional
and evolutionary patterns. eLife 4:e04775
Miyazaki S, Okada Y, Miyakawa H, Tokuda G, Cornette R, et al. 2014. Sexually dimorphic body color is
regulated by sex-specific expression of yellow gene in ponerine ant, Diacamma sp. PLOS ONE 9:e92875
Mohr SE, Hu Y, Kim K, Housden BE, Perrimon N. 2014. Resources for functional genomics studies in
Drosophila melanogaster. Genetics 197:1–18
Morandin C, Dhaygude K, Paviala J, Trontti K, Wheat C, Helanter¨a H. 2015. Caste-biases in gene expression
are specific to developmental stage in the ant Formica exsecta. J. Evol. Biol. 9:1705–18
Morandin C, Havukainen H, Kulmuni J, Dhaygude K, Trontti K, Helanter¨a H. 2014. Not only for egg
yolk—functional and evolutionary insights from expression, selection, and structural analyses of Formica
ant vitellogenins. Mol. Biol. Evol. 31:2181–93
Mott BM, Gadau J, Anderson KE. 2015. Phylogeography of Pogonomyrmex barbatus and P. rugosus harvester
ants with genetic and environmental caste determination. Ecol. Evol. 5:2798–826
Nipitwattanaphon M, Wang J, Ross KG, Riba-Grognuz O, Wurm Y, et al. 2014. Effects of ploidy and sex-locus
genotype on gene expression patterns in the fire ant Solenopsis invicta. Proc. R. Soc. B 281:1797
Noble D, Jablonka E, Joyner MJ, M¨uller GB, Omholt SW. 2014. Evolution evolves: Physiology returns to
centre stage. J. Physiol. 592:2237–44
Nygaard S, Wurm Y. 2015. Ant genomics (Hymenoptera: Formicidae): challenges to overcome and opportu-
nities to seize. Myrmecol. News 21:59–72
Nygaard S, Zhang G, Schiøtt M, Li C, Wurm Y, et al. 2011. The genome of the leaf-cutting ant Acromyrmex
echinatior suggests key adaptations to advanced social life and fungus farming. Genome Res. 21:1339–48
Ometto L, Shoemaker D, Ross KG, Keller L. 2011. Evolution of gene expression in fire ants: the effects of
developmental stage, caste, and species. Mol. Biol. Evol. 28:1381–92
Osborne KA, Robichon A, Burgess E, Butland S, Shaw RA, et al. 1997. Natural behavior polymorphism due
to a cGMP-dependent protein kinase of Drosophila. Science 277:834–36
Oster GF, Wilson EO. 1978. Caste and Ecology in the Social Insects. Princeton, NJ: Princeton Univ. Press
Oxley PR, Ji L, Fetter-Pruneda I, McKenzie SK, Li C, et al. 2014. The genome of the clonal raider ant
Cerapachys biroi. Curr. Biol. 24:451–58
Patel AD. 1990. An unusually broad behavioral repertory for a major worker in a dimorphic ant species:
Pheidole morrisi (Hymenoptera, Formicidae). Psyche: J. Entomol. 97:181–91
Peleg S, Sananbenesi F, Zovoilis A, Burkhardt S, Bahari-Javan S, et al. 2010. Altered histone acetylation is
associated with age-dependent memory impairment in mice. Science 328:753–56
Purcell J, Brelsford A, Wurm Y, Perrin N, Chapuisat M. 2014. Convergent genetic architecture underlies
social organization in ants. Curr. Biol. 24:2728–32
Purcell J, Chapuisat M. 2013. Bidirectional shifts in colony queen number in a socially polymorphic ant
population. Evolution 67:1169–80
54
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 15

NE39CH03-Gordon
ARI
25 March 2016
13:12
Rappoport N, Linial M. 2015. Trends in genome dynamics among major orders of insects revealed through
variations in protein families. BMC Genom. 16:583
Ratzka C, Gross R, Feldhaar H. 2013. Systemic gene knockdown in Camponotus floridanus workers by feeding
of dsRNA. Insectes Sociaux 60:475–84
Rehan SM, Toth AL. 2015. Climbing the social ladder: the molecular evolution of sociality. Trends Ecol. Evol.
30:426–33
Rittschof CC, Robinson GE. 2014. Genomics: moving behavioural ecology beyond the phenotypic gambit.
Anim. Behav. 92:263–70
Ross KG. 1992. Strong selection on a gene that influences reproductive competition in a social insect. Nature
355:347–49
Rosset H, Chapuisat M. 2006. Alternative life-histories in a socially polymorphic ant. Evol. Ecol. 21577–88
Roux J, Privman E, Moretti S, Daub JT, Robinson-Rechavi M, Keller L. 2014. Patterns of positive selection
in seven ant genomes. Mol. Biol. Evol. 31:1661–85
Schwander T, Helms Cahan S, Keller L. 2007. Characterization and distribution of Pogonomyrmex harvester
ant lineages with genetic caste determination. Mol. Ecol. 16:367–87
Sempo G, Detrain C. 2004. Between-species differences of behavioural repertoire of castes in the ant genus
Pheidole: a methodological artefact? Insectes Sociaux 51:48–54
Simola DF, Graham RJ, Brady CM, Enzmann BL, Desplan C, et al. 2016. Epigenetic (re)programming of
caste-specific behavior in the ant Camponotus floridanus. Science 351:aac6633
Simola DF, Wissler L, Donahue G, Waterhouse RM, Helmkampf M, et al. 2013a. Social insect genomes
exhibit dramatic evolution in gene composition and regulation while preserving regulatory features linked
to sociality. Genome Res. 23:1235–47
Simola DF, Ye C, Mutti NS, Dolezal K, Bonasio R, et al. 2013b. A chromatin link to caste identity in the
carpenter ant Camponotus floridanus. Genome Res. 23:486–96
Sirvi¨o A, Pamilo P, Johnson RA, Page RE Jr., Gadau J. 2011. Origin and evolution of the dependent lineages
in the genetic caste determination system of Pogonomyrmex ants. Evolution 65:869–84
Smith CD, Zimin A, Holt C, Abouheif E, Benton R, et al. 2011. Draft genome of the globally widespread and
invasive Argentine ant (Linepithema humile). PNAS 108:5673–78
Smith CR, Helms Cahan S, Kemena C, Brady SG, Yang W, et al. 2015. How do genomes create novel
phenotypes? Insights from the loss of the worker caste in ant social parasites. Mol. Biol. Evol. 32:2919–31
Smith CR, Mutti NS, Jasper WC, Naidu A, Smith CD, Gadau J. 2012. Patterns of DNA methylation in
development, division of labor and hybridization in an ant with genetic caste determination. PLOS ONE
7:e42433
Smith CR, Smith CD, Robertson HM, Helmkampf M, Zimin A, et al. 2011. Draft genome of the red harvester
ant Pogonomyrmex barbatus. PNAS 108:5667–72
Snyder LE. 1992. The genetics of social behavior in a polygynous ant. Naturwissenschaften 79:525–27
Snyder LE. 1993. Non-random behavioural interactions among genetic subgroups in a polygynous ant. Anim.
Behav. 46:431–39
Sokolowski MB. 1980. Foraging strategies of Drosophila melanogaster: a chromosomal analysis. Behav. Genetet.
10:291–302
Sokolowski MB, Bauer SJ. 1989. Genetic analyses of pupation distance in Drosophila melanogaster. Heredity
62:177–83
Spannhoff A, Kim YK, Raynal NJM, Gharibyan V, Su M-B, et al. 2011. Histone deacetylase inhibitor activity
in royal jelly might facilitate caste switching in bees. EMBO Rep. 12:238–43
Stuart RJ, Page RE Jr. 1991. Genetic component to division of labor among workers of a leptothoracine ant.
Naturwissenschaften 78:375–77
Suen G, Teiling C, Li L, Holt C, Abouheif E, et al. 2011. The genome sequence of the leaf-cutter ant Atta
cephalotes reveals insights into its obligate symbiotic lifestyle. PLOS Genet. 7:e1002007
Sumner S. 2014. The importance of genomic novelty in social evolution. Mol. Ecol. 23:26–28
Tataroglu O, Emery P. 2014. Studying circadian rhythms in Drosophila melanogaster. Methods 68:140–50
Toth AL, Robinson GE. 2007. Evo-devo and the evolution of social behavior. Trends Genet. 23:334–41
Trible W, Ross KG. 2015. Chemical communication of queen supergene status in an ant. J. Evol. Biol. In
press. doi: 10.1111/jeb.12799
www.annualreviews.org • Ant Genetics
55
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.

## Page 16

NE39CH03-Gordon
ARI
25 March 2016
13:12
Tsutsui ND. 2013. Dissecting ant recognition systems in the age of genomics. Biol. Lett. 9:20130416
Vander Meer R. 2012. Ant interactions with soil organisms and associated semiochemicals. J. Chem. Ecol.
38:728–45
Visscher PM, Hill WG, Wray NR. 2008. Heritability in the genomics era—concepts and misconceptions.
Nat. Rev. Genet. 9:255–66
Volny VP, Gordon DM. 2002. Genetic basis for queen-worker dimorphism in a social insect. PNAS 99:6108–
11
Volny VP, Greene MJ, Gordon DM. 2006. Brood production and lineage discrimination in the red harvester
ant (Pogonomyrmex barbatus). Ecology 87:2194–200
Wang J, Ross KG, Keller L. 2008. Genome-wide expression patterns and the genetic architecture of a funda-
mental social trait. PLOS Genet. 4:e1000127
Wang J, Wurm Y, Nipitwattanaphon M, Riba-Grognuz O, Huang Y-C, et al. 2013. A Y-like social chromo-
some causes alternative colony organization in fire ants. Nature 493:664–68
Ward PS. 2014. The phylogeny and evolution of ants. Annu. Rev. Ecol. Evol. Syst. 45:23–43
Wiernasz DC, Hines J, Parker DG, Cole BJ. 2008. Mating for variety increases foraging activity in the
harvester ant, Pogonomyrmex occidentalis. Mol. Ecol. 17:1137–44
Wilson EO. 1984. The relation between caste ratios and division of labor in the ant genus Pheidole (Hy-
menoptera: Formicidae). Behav. Ecol. Sociobiol. 16:89–98
Wurm Y, Wang J, Riba-Grognuz O, Corona M, Nygaard S, et al. 2011. The genome of the fire ant Solenopsis
invicta. PNAS 108:5679–84
Yan H, Simola DF, Bonasio R, Liebig J, Berger SL, Reinberg D. 2014. Eusocial insects as emerging models
for behavioural epigenetics. Nat. Rev. Genet. 15:677–88
Zhou X, Rokas A, Berger SL, Liebig J, Ray A, Zwiebel LJ. 2015. Chemoreceptor evolution in Hymenoptera
and its implications for the evolution of eusociality. Genome Biol. Evol. 7:2407–16
Zhou X, Slone JD, Rokas A, Berger SL, Liebig J, et al. 2012. Phylogenetic and transcriptomic analysis of
chemosensory receptors in a pair of divergent ant species reveals sex-specific signatures of odor coding.
PLOS Genet. 8:e1002930
56
Friedman· Gordon
Changes may still occur before final publication online and in print
Annu. Rev. Neurosci. 2016.39. Downloaded from www.annualreviews.org
 Access provided by City University London on 04/11/16. For personal use only.


---
*Extraction method: pymupdf*