Periodic Reporting for period 1 - EvolvAnt (Natural selection during the recurrent evolution of a major social trait)
Reporting period: 2019-05-23 to 2021-05-22
There are around 20,000 described ant species on earth, and they exhibit vast ecological and behavioural diversity. Social organization in ant colonies is one of the fundamental social traits in ant colonies and there have been multiple transitions from single-queen social organization to multiple-queen social organization. These different social organizations are associated with demographic, ecological and behavioural differences among the ant species and affect intracolony conflicts and evolutionary trade-offs. There is a huge body of theoretical studies on how selection shapes the evolution of new social systems, but which genetic mechanisms underlie such changes are yet to be thoroughly investigated.
Our project was designed to investigate the genetic mechanisms of the convergent evolution of the multiple-queen social organization from the single-queen social organization in ants. We wanted to understand the mechanism involved in such independent transitions from single-queen to multiple-queen social organization as well as the long-term effects of such transitions. We used the protein-coding genes to differentiate between ant species belonging to the two types of social organizations. We specifically focused on genes associated with reproduction, communication and immunity. For investigating the long-term effects of such evolutionary transitions on the biology of the species, we looked into the prevalence of viruses in ant colonies belonging to these two types of social organizations.
We used multiple ant species, some obligately single-queen species and some obligately multiple-queen species to address these questions. Ant species exhibiting the multiple-queen social organization are generally invasive. Hence, understanding the genetic mechanisms of such evolutionary transitions to the multiple-queen social organization would enable us to gain a better understanding of the genetic changes that are responsible for a species becoming invasive in a particular habitat. Such investigations in turn would enable us to design future research for controlling invasive species. In addition to this, the investigation involving the viral prevalence in ant colonies would enable us to predict whether they have the potential of becoming pathogen reservoirs and in turn, would enable us to design research for preventing any kind of pathogen spillover to other species.
The conclusion of the project was that there are consistent differences between species belonging to obligately single- or multiple-queen social organizations. Genes underlying cellular communication and recognition, which help in key processes like chemical communication, neurotransmission and immune response appeared to be under similar selection pressures and might have played significant roles during the independent transitions from single queen to multiple queen colony lifestyles. In addition to this, the project also found that multiple-queen colonies harbour greater viral load and viral diversity compared to the single-queen colonies.
Our project was designed to investigate the genetic mechanisms of the convergent evolution of the multiple-queen social organization from the single-queen social organization in ants. We wanted to understand the mechanism involved in such independent transitions from single-queen to multiple-queen social organization as well as the long-term effects of such transitions. We used the protein-coding genes to differentiate between ant species belonging to the two types of social organizations. We specifically focused on genes associated with reproduction, communication and immunity. For investigating the long-term effects of such evolutionary transitions on the biology of the species, we looked into the prevalence of viruses in ant colonies belonging to these two types of social organizations.
We used multiple ant species, some obligately single-queen species and some obligately multiple-queen species to address these questions. Ant species exhibiting the multiple-queen social organization are generally invasive. Hence, understanding the genetic mechanisms of such evolutionary transitions to the multiple-queen social organization would enable us to gain a better understanding of the genetic changes that are responsible for a species becoming invasive in a particular habitat. Such investigations in turn would enable us to design future research for controlling invasive species. In addition to this, the investigation involving the viral prevalence in ant colonies would enable us to predict whether they have the potential of becoming pathogen reservoirs and in turn, would enable us to design research for preventing any kind of pathogen spillover to other species.
The conclusion of the project was that there are consistent differences between species belonging to obligately single- or multiple-queen social organizations. Genes underlying cellular communication and recognition, which help in key processes like chemical communication, neurotransmission and immune response appeared to be under similar selection pressures and might have played significant roles during the independent transitions from single queen to multiple queen colony lifestyles. In addition to this, the project also found that multiple-queen colonies harbour greater viral load and viral diversity compared to the single-queen colonies.
Our project was designed to investigate the genetic mechanisms of the convergent evolution of the multiple-queen social organization from the single-queen social organization in ants. We wanted to understand the mechanism involved in such independent transitions from single-queen to multiple-queen organization. For this, we used a phylogenomic framework with multiple transitions from obligate single-queen to obligate multiple-queen social form. We used the protein coding gene content across 22 ant species. The hypothesis behind this novel approach was that while a core set of protein functions are consistently present in similar numbers in all species, the amounts of other protein types might vary between the two social forms. We have found extensive variation in protein domain content between subfamilies of ants, highlighting molecular functions likely responsible for phenotypic differences between subfamilies. Furthermore, we compared protein domains between nine species with obligate single-queen colonies to seven species whose ancestors transitioned to obligate multiple-queen colonies. We identified consistent differences between the two social organizations. Genes underlying cellular communication and recognition, which help in key processes like chemical communication, neurotransmission and immune response, thus appear to be under similar selection pressures and might have played significant roles during the independent transitions from single queen to multiple queen colony lifestyles.We now have a pipeline for this analysis and intend to include more ant species in this analysis. We expect to finalise the results in the coming months and proceed for a peer-reviewed publication.
In the other part of the project, we had proposed to study the long-term effects of such independent transitions from single-queen to multiple-queen social forms. For this, we investigated the viral load and viral diversity in the queens of the red imported fire ant, Solenopsis invicta. This was an ideal study system because it harbours both single-queen and multiple-queen social forms. We found that queens of the multiple-queen social form harbour 8.3-times higher viral load and 1.5-times higher viral diversity compared to queens from the single-queen social form. We have used a novel method of using a metagenomic sequence classification pipeline on RNA-Seq reads from the S. invicta queens of the two types of social forms. We have summed up our results in the form of a manuscript, which is currently under the peer-review process.
As a part of disseminating the results, both works have been presented as talks in multiple conferences over the last two years.
In the other part of the project, we had proposed to study the long-term effects of such independent transitions from single-queen to multiple-queen social forms. For this, we investigated the viral load and viral diversity in the queens of the red imported fire ant, Solenopsis invicta. This was an ideal study system because it harbours both single-queen and multiple-queen social forms. We found that queens of the multiple-queen social form harbour 8.3-times higher viral load and 1.5-times higher viral diversity compared to queens from the single-queen social form. We have used a novel method of using a metagenomic sequence classification pipeline on RNA-Seq reads from the S. invicta queens of the two types of social forms. We have summed up our results in the form of a manuscript, which is currently under the peer-review process.
As a part of disseminating the results, both works have been presented as talks in multiple conferences over the last two years.
We have one manuscript under peer review and another manuscript under preparation.
As for the wider impact of the project, understanding the genetic mechanisms of evolutionary transitions from single-queen to multiple-queen social organization will enable us to gain a better understanding of the genetic changes that are responsible behind a species becoming invasive in a particular habitat. Such investigations in turn will enable us to design future research for controlling invasive species. In addition to this, the investigation involving the viral prevalence in ant colonies will enable us to predict whether they have the potential of becoming pathogen reservoirs and in turn, will enable us to design research for preventing any kind of pathogen spillover to other species.
As for the wider impact of the project, understanding the genetic mechanisms of evolutionary transitions from single-queen to multiple-queen social organization will enable us to gain a better understanding of the genetic changes that are responsible behind a species becoming invasive in a particular habitat. Such investigations in turn will enable us to design future research for controlling invasive species. In addition to this, the investigation involving the viral prevalence in ant colonies will enable us to predict whether they have the potential of becoming pathogen reservoirs and in turn, will enable us to design research for preventing any kind of pathogen spillover to other species.