| Symposium proposal | |
| Organizer: | Guojie Zhang (University of Copenhagen) |
| The social insects, including bees, wasps, ants and some termites, present highly advance social system and complex social behaviors. The social colony of these species consists up to millions of individuals with clear social role divisions. The queen and male castes are the only individuals in the colony with full reproductive ability and are analogous to the germ cells in metazoan, while the sterilized worker and soldier castes are analogous to the somatic cells. Therefore, the social insect colony is often recognized as superorganism. Darwin was once puzzled by the social organization and the altruistic behaviors in these animals. This was latterly explained by Hamilton's rule, which popularized the kin selection theory that has been also widely applied in understanding the social evolution in other species including human. Nowadays, the social insects have been frequently used as models for the study of social evolution, social learning, and division of labors in social organization from both ecological level and molecular level. Cross-disciplinary methods have often been used in study of social insects on their phylogeny, behavior ecology, neuroanatomy, and gene regulations. This symposium will highlight some of most recent development in this filed and includes speakers from Japan, Australia, India, and China. | |
S16-1
Better together: group attack, swarm intelligence and collective resilience in invertebrate societies
Tanya Latty1
Affiliations are not specified
Invertebrates display a wide variety of social behaviours ranging from group hunting to the amazingly complex societies found in eusocial insects such as honeybees, termites and ants. Working together in groups can give invertebrates access to abilities that far exceed the capabilities of solitary individuals. In this talk, I will discuss the usefulness of a comparative approach to understanding social behaviours in multiple contexts. I will start by discussing the divergent trail construction strategies used by Argentine ants (Linepithema humile) and Australian meat ants (Iridomyrmex purpureus) to balance the competing objectives of robustness, cost and efficiency. While both species face similar challenges, they have evolved very different approaches to solving this complex problem. Next, I will discuss two examples of group foraging in non-eusocial invertebrates: the tree-killing mountain pine beetle (Dendroctonus ponderosae) and the unusual glue-shooting velvet worm (Euperipatoides rowelli). Both species use forms of social foraging to hunt and incapacitate larger and/or more dangerous prey than any individual could on their own. Last, I will argue that understanding the mechanisms and evolution of a wide range of social systems can be important in the conservation of invertebrate biodiversity.
S16-2
Genomic imprinting and the origin of eusociality in termites
Kenji Matsuura1, Hiromu Ito1,2, Kazuya Kobayashi1, Haruka Osaki1,3, Jin Yoshimura1,4, Edward Vargo1,5
1Kyoto University
2Nagasaki University
3Kyushu University
4Shizuoka University
5Texas A&M University
2Nagasaki University
3Kyushu University
4Shizuoka University
5Texas A&M University
The origin of eusociality, altruistically foregoing personal reproduction to help others, has been a long-standing paradox since the time of Darwin. Explanations for the evolution of altruistic behavior have focused on inclusive fitness theory for the past five decades. Most eusocial insects and eusocial rodents likely evolved from subsocial precursors, in which older offspring “helpers” contribute to the development of younger siblings without a permanent sterile caste. The driving mechanism for the transition from subsociality to eusociality remains an enigma because individuals in subsocial groups are subject to direct natural selection rather than kin selection. We propose a theory to explain the origin of eusociality via genomic imprinting. Based on the theory, we build a model and demonstrate that natural selection promotes eusociality in subsocial groups when parental reproductive capacity is linked to a delay in the sexual development of offspring due to sex-antagonistic action of transgenerational epigenetic marks. Parental monogamy, within-nest iteroparity, high work performance of helpers and long colony longevity are necessary but insufficient conditions for lifetime sterile workers to evolve. Focusing on termites, our model provides the missing evolutionary link to explain the evolution of eusociality from their subsocial wood-feeding cockroach ancestors, and provides a novel framework for understanding the origin of eusociality in diverse taxa.
S16-3
Unraveling the evolution of odorant receptor number across social and non-social Hymenoptera
Shubham Gautam1, Sean McKenzie2, Julian Katzke1, Takuma Yoshida1, Francisco Hita Garcia1, Shûhei Yamamoto3, Evan P Economo1
1Biodiversity and Biocomplexity Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Japan
2Genomic Applications, Oxford Nanopore Technologies, Oxford, United Kingdom
3The Hokkaido University Museum, Sapporo, Japan
2Genomic Applications, Oxford Nanopore Technologies, Oxford, United Kingdom
3The Hokkaido University Museum, Sapporo, Japan
Sensing and discriminating chemical cues is essential for many animals to perform adaptive behaviors. In social insects, cuticular hydrocarbons facilitate olfactory identification and communication between nestmates. At the molecular level, olfactory discrimination of chemical cues is achieved through one neuron-one receptor strategy. Each olfactory receptor neuron (ORN) expresses one odorant receptor (Or) gene, while axons from all ORNs expressing the same gene reach out to the same glomeruli in the antennal lobes of the brain. Recent studies based on a limited number of taxa proposed that lineages representing independent evolution of eusociality may have independently evolved expanded odorant receptor gene repertoires, particularly the 9-exon subfamily, suggesting an important role of these genes in the evolution of eusociality. This putative expansion at molecular level would correspond with the expansion of the T6/Tb cluster of glomeruli in the antennal lobes of the Hymenopteran brain. However, this hypothesis has not been tested with a broad comparative analysis. Here, we compile existing genomic data on Or gene repertoires, add new data from neuroanatomical study of a variety of Hymenopteran lineages including a remarkable ~100my old fossil ant, to shed light on the evolution of odorant receptors across the group. Our provisional results suggest that the expansion of the T6 glomeruli cluster may have predated the evolution of ants and that T6 glomeruli expansions do not appear to correlate with the evolution of eusociality. The evolutionary patterns of T6 and total glomerulus number are complex, highlighting a number of questions that need to be addressed with future work.
S16-4
Single cell transcriptomic atlas reveal neural mechanism of division of labor in ant superorganism
Weiwei Liu1
1State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming，China
An ant colony with behavioral specialization and functional integration across sexes and castes is considered as a superorganism, yet the molecular and cellular mechanisms underlying division of labor in an ant superorganism remains obscure. In this study, we produced a comprehensive single cell transcriptomic atlas of Momomorium pharaonis whole brains, consisting of 206,307 single cell transcriptomes from the full panel of adult forms of a typical ant colony, namely worker, queen, gyne (unmated queen), and male. The 4 M. pharaonis adult forms are differentiated by sex, caste or reproductive role respectively and are behaviorally specialized for reproduction or other colony maintenance tasks. We found that brains of the 4 adult forms are composed of same cell types in remarkably distinct proportions. The frequency changes of different cell types are behaviorally relevant for sex/caste/reproductive role specific division of labor in a colony. We also disclosed the cellular and molecular features of ant brains that are conserved or diversified during evolutionary transition from solitary to social living by comparing brain single cell atlas across ant species M. pharaonis, H. saltator and fruit fly D. melanogaster. In contrast to the solitary fly, the ant mushroom body intrinsic Kenyon cells display particularly high diversity and increased abundance. Neurons in the optic lobe, however, are less diversified and likely play conserved roles in regulating courtship and circadian behaviors across insect lineages. Apart from the above, we also identified conserved cell type changes that are associated with longevity and fecundity shifts after a queen is inseminated, which include the increase of ensheathing glia and a population of dopamine-regulated Dh31-expressing neurons. These results together shed light on the adaptive brain changes toward evolution of social life and provide novel insights into the neural basis underlying division of labor in an ant superorganism.
S16-5
The evolution of ant community assembly in Pacific Island
Cong Liu1,2, Alexander Mikheyev3, Evan Economo1
1Okinawa Institute of Science and Technology Graduate University
2Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University
3Australian National University
2Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University
3Australian National University
Biologists have long sought to understand the evolutionary dynamics of island community assembly, and the study of remote island biotas has been particularly informative for generating and testing theoretical frameworks. While reconstructing the dynamics of colonization and post-colonization evolutionary changes has long been a challenge, emerging next-generation technologies for molecular and morphological analysis offer new data streams that can be brought to bear on the problem. Here, we examined the evolutionary assembly of the ant community in the Fijian archipelago by integrating the “community genomics” approach and x-ray microtomography/3D morphometrics in a comparative framework. We find that the highly endemic Fijian ant fauna was assembled through a series of colonizations and radiations over millions of years, followed by more recent arrivals of regionally widespread and alien species from outside the region. Within the radiations of those highly endemic species, we observed a strong ecomorphological diversification and the subsequent ecological niche shift. Using demographic modeling, we show that the vast majority of endemic species are in decline, while the populations of non-endemic species are expanding. Taken together, this study advances our knowledge of community assembly by unraveling the evolutionary assembly of Fijian ants.
