Biology subjects

Viljakainen, L.

Publications and source records attributed to Viljakainen, L..

6 recordsLinked to original sources

bioRxiv2026

Viral infection patterns in ants are affected by colony structure and phylogenetic lineage

Across ant species, there are differences in how their societies are structured. Single-queened (monogynous) societies only have one reproducing queen in the colony, and new queens disperse and start colonies independently. In multiple-queened (polygynous) societies, the colony instead can contain several reproductive queens, and newborn queens often remain and reproduce within their natal colony. As a result, polygynous societies are comparatively larger, more genetically diverse, and can span large areas through several interconnected nests, whereas monogynous societies are typically smaller in scale. In this study, we investigated how these different social structures, as well as their phylogenetic lineage, affect the diversity (number of virus species per ant sample) and abundance (number of viral sequences per sample) of viruses in ants. We produced pooled RNA sequence libraries from 15 ant species, representing both monogynous and polygynous social structures, and the two largest ant subfamilies: Formicinae and Myrmicinae, with each library containing the RNA of up to 400 individual worker ants from a single population. We identified 168 virus species in total, of which 152 species were new to science. Out of these 168 viruses, 59 were active viruses based on the host immune response. We observed that polygynous ant species harbor a higher diversity of viruses and also tend to have higher virus abundance compared to monogynous species. Also, the ant subfamily Myrmicinae had a higher virus diversity than Formicinae. These findings highlight how social structure and evolutionary history shape viral diversity in ants.

genomics↗

bioRxiv2025

A novel supergene controls queen size and colony social organization in the ant Myrmica ruginodis

In some ant species, the size of queens is dimorphic, with larger queens dispersing to form single-queen colonies and smaller queens remaining in natal colonies as part of multiple-queen societies. These alternative reproductive strategies influence colony kin structure and worker behavior, and their many independent origins make them ideal systems to study parallel evolution of genome organization and adaptability. We investigate the genetic basis of alternative reproductive strategies in the queen-size dimorphic ant Myrmica ruginodis by sampling 95 queens from 31 colonies in southern Finland. Whole-genome sequencing revealed a novel 9 Mb supergene associated with both queen size and social organization. Queens homozygous for the AA haplotype were larger and found only in single-queen colonies, while queens in multiple-queen colonies were smaller and contained only AB and BB genotypes. This supergene is not homologous to previously identified supergenes in ants, suggesting it was formed by a unique evolutionary pathway.

evolutionary biology↗

bioRxiv2024

Population Genomics of the Invasive Argentine Ant (Linepithema humile) - Adaptive Evolution in the Introduced Supercolonies Despite Low Genetic Diversity

The Argentine ant (Linepithema humile), native to South America, has spread globally over the past 150 years, forming extremely large supercolonies in its introduced range. Despite the recent demographic history, including founder effects, Argentine ants thrive in the introduced range and displace native ant species. We adopted a comprehensive approach to investigate selection signals across the whole genome of this highly invasive species, with a specific focus on introduced supercolonies. We also investigated genome-wide diversity and divergence patterns and compared the results with earlier microsatellite marker data studies. We used pooled whole-genome sequence data from 100 workers from the species' native range and each of the three invasive supercolonies -- European Main, Catalonia, and Chile. Invasive supercolonies harboured low genetic diversity and were genetically highly differentiated. Despite this, we could detect signs of positive selection in their genomes. Some of the selected genes showed parallel adaptive evolution in invasive supercolonies. Furthermore, there were no signs that a social organisation based on unrelated workers had led to impaired adaptability (genetic meltdown). We conclude that introduced Argentine ant supercolonies evolve adaptively, indicating that founder effects, low genetic diversity and supercolony social organisation do not always hamper species adaptability.

genomics↗

bioRxiv2024

The loss of a supergene in obligately polygynous Formica wood ant species

Some of the most striking examples of phenotypic variation within species are controlled by supergenes. However, most research on supergenes has focused on their emergence and long-term maintenance, leaving the later stages of their life cycle largely unexplored. Specifically, what happens to a derived supergene haplotype when the trait it controls reaches fixation? Here we answer this question using the ancient supergene system of Formica ants, where (monogynous) single-queen colonies carry only the ancestral haplotype M while the derived haplotype P is exclusive to (polygynous) colonies with multiple queens. Through comparative genomics of all seven European wood ant species, we found that the P haplotype was present in only one of the three obligate polygynous species (F. polyctena). In the two others (F. aquilonia and F. paralugubris) the P haplotype was completely missing except for duplicated P-specific paralogs of two genes, Zasp52 and TTLL2, with Zasp52 being directly involved in wing muscle development. We hypothesize that these genes play a direct role in polygyny and contribute to differences in body size and/or dispersal behaviour between monogynous and polygynous queens. A complete lack of P/P genotypes among the 136 workers suggest strong selection against such genotypes. While our analyses did not reveal evidence of increased mutation load on the P, it is possible that this skew in genotype distributions is driven by a few loci with strong fitness effects. We propose that selection to escape P-associated fitness costs underlies the loss of this haplotype in obligate polygynous wood ants.

genomics↗

bioRxiv2022

Antiviral immune response reveals host-specific virus infections in natural ant populations

Hosts can carry many viruses in their bodies, but not all of them cause disease. We studied ants as a social host to determine both their overall viral repertoire and the subset of actively infecting viruses across natural populations of three subfamilies: the Argentine ant (Linepithema humile, Dolichoderinae), the invasive garden ant (Lasius neglectus, Formicinae) and the red ant (Myrmica rubra, Myrmicinae). We used a dual sequencing strategy to reconstruct complete virus genomes by RNA-seq and to simultaneously determine the small interfering RNAs (siRNAs) by small RNA sequencing (sRNA-seq), which constitute the host antiviral RNAi immune response. This approach led to the discovery of 41 novel viruses in ants and revealed a host-ant specific RNAi response (21 vs. 22 nt siRNAs) in the different ant species. The efficiency of the RNAi response (sRNA/RNA read count ratio) depended on the virus and the respective ant species, but not its population. Overall, we found the highest virus abundance and diversity per population in Li. humile, followed by La. neglectus and M. rubra. Argentine ants also shared a high proportion of viruses between populations, whilst overlap was nearly absent in M. rubra. Only a single of the total 59 viruses in our study caused active infection in more than one ant species, whilst six viruses infected one, but only contaminated another ant species. Disentangling active infection from contamination thus allowed us to show high host-specificity of active viral infections versus a decent degree of spillover of non-infecting viral contaminants across ant species, providing relevant information for ecosystem management.

microbiology↗

bioRxiv2022

Genetic modification of the ant Lasius niger using CRISPR-Cas9 technology

CRISPR-Cas9 has become one of the most prominent gene editing tools available and it has been utilized in various organisms from bacteria to fungi, plants, and animals. In this study, we developed a CRISPR-Cas9 protocol for the black garden ant Lasius niger, a common and easily available study species for lab and field environments. To create indel mutations using CRISPR-Cas9 in L. niger, we targeted three different locations in a well-studied eye pigmentation gene cinnabar, generating several mutations that disrupt the ommochrome biosynthesis pathway and result in the lack of this pigment and therefore, abnormal eye coloration in adult workers. We also developed a protocol to collect L. niger eggs, inject them with CRISPR-Cas9 construct, and rear the eggs into mature adult workers with assistance of nursing workers. We demonstrated for the first time with L. niger that CRISPR-Cas9 is an excellent tool to create targeted mutations for this species. Our protocol can be referred to when developing similar studies for other species of ants and eusocial insects.

genetics↗