Trends in Genetics
ReviewThe genomic impact of 100 million years of social evolution in seven ant species
Section snippets
Ant genomes: tools to study biological and social complexity
Ants (Hymenoptera, Formicidae; see Glossary) comprise a dominant component of most terrestrial habitats. The more than 14000 described species (http://www.antweb.org) show an enormous diversity in life-history features, ecological and behavioral adaptations and social organization, and are a prime example of a complex adaptive system 1, 2, 3, 4, 5. Current evidence suggests that the last common ancestor of the ants lived during the Jurassic and Cretaceous periods, 140–168 million years ago
Genomic and genetic features of the seven sequenced ant species
The use of different sequencing technologies and depth of coverage across the sequenced ant species (10.5–123×) has yielded genome assemblies with a ten-fold range of median scaffold sizes (N50 from 598 kb to 5154 kb; Table 2). The overall size of these genomes ranges from 250 Mb to 753 Mb, and most of the variation in genome size is attributable to differences in repetitive element content (Table 2). Solenopsis invicta is the largest ant genome sequenced (353 Mb assembled) [17] and, although no
Epigenetic control of caste determination
DNA methylation and histone modifications contribute to gene expression regulation and can be stably transmitted between cell division events [39]. Unlike genetic information, which changes slowly over the course of multiple generations, such epigenetic information can change quickly within an individual in response to changing environmental conditions (e.g. temperature, diet, and stress). Although an individual is only endowed with one nuclear genome, it can have multiple epigenomes that
Genetic control of caste programs
Pogonomyrmex barbatus promises the most insight into the genetic and epigenetic factors influencing caste determination because it is the only sequenced ant species known to use both environmental (ECD) and genetic forms of caste determination (GCD). Hence, genetic markers allow queen- or worker-destined individuals to be distinguished regardless of developmental stage 45, 46. This makes it possible to analyze stage-specific expression data, allowing for the identification of the developmental
Concluding remarks and future perspectives
The release of seven sequenced ant genomes and the development of new genomic tools for ants has laid the groundwork for an exciting new era of socio- and ant genomics 13, 14. It is now possible to study the molecular basis of social behavior in a second taxon that evolved eusociality independently from the honeybee lineage. The first analysis of the seven ant genomes revealed that ants have a different sociogenome compared with that of the honeybee and that there is also significant variation
Acknowledgments
The authors would like to thank Alex Wild and Myrmecos.net for providing images of the sequenced ant species used in Figure 1. JG and CRS were supported by a grant from the NSF (IOS-0920732). CDS was supported by a grant from the NIMH (5SC2MH086071). DS is supported by a Howard Hughes Medical Institute Collaborative Innovation Award #200900 to D. Reinberg, S. Berger, and J. Liebig. YW was supported by a European Research Council grant to Laurent Keller and JR was supported by a Swiss NSF grant
Glossary
- Caste
- a subset of individuals in an insect colony that are characterized either behaviorally or morphologically.
- Environmental caste determination (ECD)
- the differentiation between queens and worker castes is determined by environmental factors, such as exposure to hormones, temperature, or alternate food sources. This is thought to be the main mechanism of caste determination across eusocial species.
- Epigenetics
- the study of heritable molecular differences resulting in a measurable phenotype that
References (75)
DNA methylation is widespread across social Hymenoptera
Curr. Biol.
(2008)Genotype effect on regulation of behaviour by vitellogenin supports reproductive origin of honeybee foraging bias
Anim. Behav.
(2010)- et al.
Insects as innovative models for functional studies of DNA methylation
Trends Genet.
(2011) Nature versus nurture in social insect caste differentiation
Trends Ecol. Evol.
(2010)- et al.
Aging and development in social insects with emphasis on the honey bee, Apis mellifera L
Exp. Gerontol.
(2001) - et al.
Social insects as a model to study the molecular basis of ageing
Exp. Gerontol.
(2006) Isolation from an ant Myrmecia gulosa of two inducible O-glycosylated proline-rich antibacterial peptides
J. Biol. Chem.
(1998)- et al.
The Ants
(1990) - et al.
The Superorganism
(2009) Ants (Formicidae): models for social complexity
Cold Spring Harb. Protoc.
(2009)