Biology subjects

Seifert, B.

Publications and source records attributed to Seifert, B..

5 recordsLinked to original sources

bioRxiv2024

Introgression and divergence in a young species group

The process of speciation concerns often not only pairs of species but rather groups of diverging and interacting taxa, as highlighted by recent research. Hence, to understand the evolution of species diversity and their persistence, it is crucial to understand how gene flow and evolution of reproductive isolation shape groups of closely related species. Using resequencing data, we disentangle here genomic patterns of divergence and introgression in five Formica rufa group wood ant species that are at the early stage of speciation. We first revise earlier mitochondrial phylogenies with a nuclear genomic tree, and demonstrate then introgression that is in line with observations of their current day natural hybridisation. Investigating the genome-wide differentiation and divergence we find correlations between population genetic parameters of divergence, differentiation, and diversity, that are in line with theoretical expectations for young species. Despite previously found evidence for polygenic species barriers, our data lacks the genome-wide correlation between differentiation and divergence that would be expected under a model of polygenic barriers. The likely explanation for this lack is the dominating effect of ancestral diversity at these early stages of speciation. As hybridisation has led to both deleterious and adaptive consequences within the group, we examined the signatures of introgression. We find no strong positive correlation between introgression and recombination, suggesting introgression does not have a predominantly deleterious effect. We also infer low diversity in the genomic regions with high proportions of introgression, consistent with the idea that selection has locally favoured introgression. This could be due to sharing of adaptive alleles or reduction of genetic load in the receiving species. Interestingly, gene flow in this group could potentially cross multiple species boundaries even in the absence of direct interbreeding between all the species. We discuss the long-term benefits and costs of introgression in young species, including the effect of environmental fluctuations and multi-species introgression.

evolutionary biology↗

bioRxiv2024

TXNIP mediates LAT1/SLC7A5 endocytosis to reduce amino acid uptake in cells entering quiescence

Entry and exit from cellular quiescence require dynamic adjustments in nutrient acquisition, yet the mechanisms by which quiescent cells downregulate amino acid (AA) transport remain poorly understood. Here, we demonstrate that cells entering quiescence select plasma membrane-resident AA transporters for endocytosis and lysosomal degradation, to match AA uptake with reduced translation. We identify the -arrestin TXNIP as a key regulator of AA uptake during quiescence, since it mediates the endocytosis of the SLC7A5-SLC3A2 (LAT1-4F2hc) transporter complex in response to reduced AKT signaling. Mechanistically, TXNIP interacts with HECT-type ubiquitin ligases to facilitate transporter ubiquitination. Loss of TXNIP disrupts this regulation, resulting in dysregulated AA uptake, sustained mTORC1 signaling, and accelerated quiescence exit. A novel TXNIP loss-of-function mutation in a patient with severe metabolic disease further supports its role in nutrient homeostasis and human health. These findings highlight TXNIPs role in controlling SLC7A5-SLC3A2 mediated AA acquisition with implications for quiescence biology and disease.

cell biology↗

bioRxiv2023

Extensive hybridisation between multiple differently adapted species may aid persistence in a changing climate

Hybridisation and gene flow can have both deleterious and adaptive consequences for natural populations and species. To better understand the extent and consequences of hybridisation in nature, information on naturally hybridising non-model organisms is required, including characterising the structure and extent of natural hybrid zones. Here we study natural populations of five keystone mound-building wood ant (Formica rufa group) species across Finland. No genomic studies across the species group exist and the extent of hybridisation and genomic differentiation in sympatry is unknown. Combining genome-wide and morphological data, we show that Formica rufa, F. aquilonia, F. lugubris, and F. pratensis form distinct gene pools in Finland. We demonstrate more extensive hybridisation than previously thought between all five species and reveal a mosaic hybrid zone between F. aquilonia, F. rufa and F. polyctena. We show that hybrids between these climatically differently adapted species occupy warmer habitats than the cold-adapted parent F. aquilonia. This suggests hybrids occupy a different microclimatic niche compared to the locally abundant parent. We propose that wood ant hybridisation may increase with a warming climate, and warm winters, in particular, may provide a competitive advantage for the hybrids over F. aquilonia in the future. In summary, our results demonstrate how extensive hybridisation may help persistence in a changing climate. Additionally, they provide an example on how mosaic hybrid zones can have significant ecological and evolutionary consequences because of their large extent and independent hybrid populations that face both ecological and intrinsic selection pressures.

evolutionary biology↗

bioRxiv2021

Whole-genome analysis of multiple wood ant population pairs supports similar speciation histories, but different degrees of gene flow, across their European range

The application of demographic history modeling and inference to the study of divergence between species is becoming a cornerstone of speciation genomics. The demographic history is usually reconstructed by analysing a single population from each species, assuming that the divergence history inferred between these populations represents the actual speciation history. However, this assumption is rarely explicitly tested, and it may not be met when species diverge with gene flow. For instance, secondary contact between two species after a range expansion may be confined into a specific geographic region. In this study, we tested to what extent the divergence history inferred from two heterospecific populations would vary depending on their geographic locations, using mound-building red wood ants. The wood ant species Formica polyctena and F. aquilonia have contrasting distributions in Europe and naturally hybridize in Finland. We first performed whole-genome resequencing of 20 individuals sampled in multiple populations across both species ranges. We then reconstructed the divergence histories of distinct heterospecific population pairs using a coalescent-based approach. We found that the analysis of these different population pairs always supported a scenario of divergence with gene flow, suggesting that species divergence started in the Pleistocene (ca. 500 kya) and occurred with continuous asymmetrical gene flow from F. aquilonia to F. polyctena until a recent time, when migration stopped (2-19 kya, depending on the population pair considered). However, we found support for contemporary gene flow in the sympatric population pair from Finland, where hybrids have been described. Overall, our results suggest that divergence histories reconstructed from a few individuals may be reliable and applicable at the species level. Nonetheless, the geographical context of populations chosen to represent their species should be taken into account, as it may affect estimates of migration rates between species when gene flow is heterogeneous across their geographical ranges.

evolutionary biology↗

bioRxiv2020

Cytoplasmic incompatibility between Old and New World populations of a tramp ant

As we enter the Anthropocene, the evolutionary dynamics of species will change drastically, and as yet unpredictably, due to human activity. Already today, increases in global human traffic have resulted in the rapid spread of species to new areas, leading to the formation of geographically isolated populations. These go on to evolve in allopatry, which can lead to reproductive isolation, and potentially, the formation of new species. Surprisingly, little is known about such eco-evolutionary processes in ants, even though numerous invasive ant species are globally distributed in geographically isolated populations. Here, we describe the first case of cytoplasmic incompatibility (CI) between populations of a cosmotropic distributed tramp ant with Asian roots, Cardiocondyla obscurior, which has acquired a novel Wolbachia strain in the New World. Our study uncovers the first symbiont-induced mechanism of reproductive isolation in ants, providing a novel perspective on the biology of globally distributed ants.

evolutionary biology↗