Biology subjects

Wurm, Y.

Publications and source records attributed to Wurm, Y..

11 recordsLinked to original sources

bioRxiv2025

Minimal overlaps in responses to insecticides between pollinator species

Insecticides are important for protecting crops from agricultural pests, yet their use inadvertently drives global declines in beneficial insects, including pollinators. Insecticide regulation relies on the assumption that model bee species adequately represent responses to exposure across the diversity of insect taxa, despite over 479 million years of evolutionary divergence and a limited understanding of how exposure effects vary across insect orders. Here, using comparative whole-brain transcriptomics, we show differences in molecular responses to modern insecticides across evolutionary distant pollinator lineages: butterflies, flies, and bees. Within each of the four species studied, different insecticides (sulfoxaflor and clothianidin) triggered broadly similar gene regulatory responses. In surprising contrast, exposure impacts differed sharply among species, with no genes or pathways being consistently affected. Strikingly, we found that sulfoxaflor, approved based on its supposed safety for bees, causes more disruptions in non-bee pollinators than the restricted neonicotinoid clothianidin, revealing a critical blind spot in current assessment protocols. Our findings demonstrate that over large evolutionary timescales, species-level differences can outweigh variations in insecticide chemical structures in shaping the effects of insecticide exposure. These interspecific differences likely reflect distinct physiological and metabolic traits shaped over tens to hundreds of millions of years. Together, our findings highlight the urgent need to reevaluate insecticide safety assessments to incorporate phylogenetic diversity, potentially explaining why regulatory efforts have failed to halt pollinator declines despite stricter testing requirements. Significance StatementInsecticide regulations are based on a narrow set of test species, overlooking the evolutionary and functional diversity among pollinators. Here, we show that molecular responses to insecticides differ more between species than between chemicals, even when targeting the same neural receptors. Strikingly, an insecticide considered safe for bees caused greater molecular disruption in non-bee pollinators. Our findings challenge current assumptions in pesticide risk assessment and suggest that using surrogate species can misrepresent broader ecological risks. By revealing species-specific vulnerabilities rooted in millions of years of divergent evolution, this study underscores the need for a more inclusive and phylogenetically informed approach to protecting pollinator biodiversity.

evolutionary biology↗

bioRxiv2024

Acute and chronic pesticide exposure trigger fundamentally different molecular responses in bumble bee brains

Beneficial wild insects including pollinators encounter various pesticide exposure conditions, from brief high concentrations to continuous low-level exposure. To effectively assess the environmental risks of pesticides, it is critical to understand how different exposure patterns influence their effects. Unfortunately, this knowledge remains limited. To clarify whether different exposure schemes disrupt the physiology of pollinators in similar manners, we exposed bumble bees to acute and chronic treatments of three different pesticides: Acetamiprid, clothianidin, and sulfoxaflor. Gene expression profiling enabled us to compare the effects of these treatments on the brain in a high-resolution manner. There were two main surprises: First, acute and chronic exposure schemes affected largely non-overlapping sets of genes. Second, different pesticides under the same exposure scheme showed more comparable effects than the same pesticide under different exposure schemes. Acute exposure caused up-regulation of stress response mechanisms causing distinct regulatory changes, rather than amplifying the effects of prolonged low-dose exposure that affected predominantly immunity and energy metabolism. These findings show that the mode of exposure critically determines the effects of pesticides. Our results signal the need for safety testing practices to better consider mode-of-exposure dependent effects and suggest that transcriptomics can support such improvements.

ecology↗

bioRxiv2024

A neonicotinoid pesticide causes tissue-specific gene expression changes in bumble bees

Pesticides often harm beneficial insect pollinators, impairing their ability to navigate the environment, learn, fight off disease, and reproduce. Understanding the mechanisms behind these disorders is essential for improving pesticide risk assessments. To test whether pesticide exposure induces similar or distinct transcriptional responses across tissues, we administered field-realistic dose of the common neonicotinoid clothianidin to Bombus terrestris bumble bees. We then measured gene expression in brains, hind femurs, and Malpighian tubules. Our analyses revealed that 82% of gene expression differences were tissue-specific. Although genes associated with energy metabolism were consistently down-regulated across all tissues, pesticide exposure primarily affected core tissue functions, namely genes linked to ion transport in the brain, muscle function in the hind femur, and detoxification in Malpighian tubules. Furthermore, while the brain holds the highest abundance of pesticide target receptors, other tissues showed more substantial differences in gene expression magnitude. These findings reveal that pesticide exposure causes complex, tissue-specific effects rather than a uniform body-wide response. Our study provides a mechanistic basis for the severe effects of pesticide exposure on bees and shows how transcriptomics can help pinpoint the most affected areas and processes across the body. Accordingly focusing toxicological assays could significantly improve the precision of pesticide safety evaluations.

ecology↗

bioRxiv2022

No supergene despite social polymorphism in the big-headed ant Pheidole pallidula

Ant colonies ancestrally contained one queen and her non-reproductive workers. This is also the case for many but not all colonies of the Mediterranean big-headed ant Pheidole pallidula. Indeed, this species also has a derived form of social organization with multiple reproductive queens in the colony. The co-existence of two social forms also independently evolved in three other lineages of ants. In each of those lineages, variants of a supergene region of suppressed recombination determine social form. This is likely because supergene regions can link advantageous combinations of alleles from multiple loci. We thus hypothesized that a supergene region also determines colony queen number in the big-headed ant. To test this, we performed extensive population genetic analyses and genomic comparisons. We find no evidence of a supergene-like region with differentiation between single- and multiple-queen colonies. Our results show that a complex social polymorphism can evolve and be maintained without supergenes.

evolutionary biology↗

bioRxiv2021

Individual-based modeling of genome evolution in haplodiploid organisms

Ants, bees, wasps, bark beetles, and other species have haploid males and diploid females. Although such haplodiploid species play key ecological roles and are threatened by environmental changes, no general framework exists for simulating their genetic evolution. Here, we use the SLiM simulation environment to build a novel model for individual-based forward simulation of genetic evolution in haplodiploid populations. We compare the fates of adaptive and deleterious mutations and find that selection is more effective in haplodiploid species than in diploid species. Our open-source model will help understand the evolution of sociality and how ecologically important species may adapt to changing environments.

evolutionary biology↗

bioRxiv2021

Parameter exploration improves the accuracy of long-read genome assembly

Long-molecule sequencing is now routinely applied to generate high-quality reference genome assemblies. However, datasets differ in repeat composition, heterozygosity, read lengths and error profiles. The assembly parameters that provide the best results could thus differ across datasets. By integrating four complementary and biologically meaningful metrics, we show that simple fine-tuning of assembly parameters can substantially improve the quality of long-read genome assemblies. In particular, modifying estimates of sequencing error rates improves some metrics more than two-fold. We provide a flexible software, CompareGenomeQualities, that automates comparisons of assembly qualities for researchers wanting a straightforward mechanism for choosing among multiple assemblies.

bioinformatics↗

bioRxiv2021

Genomic signatures of recent adaptation in a wild bumblebee

Behavioral experiments and analyses of observation records have shown that environmental changes threaten insect pollinators, creating risks for agriculture and ecosystem stability. Despite their importance, we know little about how wild insects or other animals can adapt in response to environmental pressures. To understand the genomic bases of adaptation in an ecologically important pollinator, we analyzed genomes of Bombus terrestris bumblebees collected across Great Britain. We reveal extensive genetic diversity within this population, and strong signatures of recent adaptation throughout the genome. More specifically, we find that selection recently affected key processes underpinning environmental interactions, including neurobiology, wing development, and response to xenobiotics. We also discover unusual features of the genome, including a 53-gene region that lacks genetic diversity in many bee species, and a horizontal gene transfer from a Wolbachia bacteria. The genetic diversity and gene flow we observe for this species could support its resilience to ongoing and future challenges. Overall, we provide important insight on the genetic health of an ecologically and economically important pollinator and reveal mechanisms by which it has recently adapted. The approach we used could help to understand how species differ in their adaptive potential, and to develop conservation strategies for those most at risk.

evolutionary biology↗

bioRxiv2021

Recurring adaptive introgression of a supergene that determines social organization

Introgression has been proposed as an essential source of adaptive genetic variation. However, a key barrier to adaptive introgression is that recombination can break down combinations of alleles that underpin many traits. This barrier might be overcome in supergene regions, where suppressed recombination leads to joint inheritance across many loci. Here, we study the evolution of a large supergene region that determines a major social and ecological trait in Solenopsis fire ants: whether colonies have one queen or multiple queens. Using coalescent-based phylogenies built from the genomes of 365 haploid fire ant males, we show that the supergene variant responsible for multiple-queen colonies evolved in one species and repeatedly spread to other species through introgressive hybridization. This finding highlights how supergene architecture can enable a complex adaptive phenotype to recurrently permeate species boundaries.

evolutionary biology↗

bioRxiv2020

Genomic architecture and evolutionary conflict drive allele-specific expression in the social supergene of the red fire ant

Supergenes are genomic regions of suppressed recombination that underlie complex polymorphisms. Despite the importance of such regions, our empirical understanding of their early evolution is limited. The young "social" supergene of the fire ant Solenopsis invicta provides a powerful system for disentangling the roles of evolutionary conflict and the implications of suppressed recombination. We used population genomics to identify genetic differences between supergene variants and gene expression analyses across different populations, castes and body parts to characterize allelic expression differences for the hundreds of genes in the supergene. We find that the expression of most genes is independent of social form or supergene variant, in line with the young age of this system. Many of the genes with allelic expression differences, however, show a pattern consistent with gene degeneration due to suppressed recombination. In contrast, a small portion of the genes has the signature of evolutionary conflict between social forms.

molecular biology↗

bioRxiv2018

The first draft genomes of the ant Formica exsecta, and its Wolbachia endosymbiont reveal extensive gene transfer from endosymbiont to host.

The wood ant Formica exsecta (Formicidae; Hymenoptera), is a common ant species throughout the Palearctic region. The species is a well established model for studies of ecological characteristics and evolutionary conflict. In this study, we sequenced and assembled draft genomes for Formica exsecta and its endosymbiont Wolbachia. The draft F. exsecta genome is 277.7 Mb long; we identify 13,767 protein coding genes for which we provide gene ontology, and protein domain annotations. This is also the first report of a Wolbachia genome from ants, and provides insights into the phylogenetic position of this endosymbiont. We also identified multiple horizontal gene transfer events (HGTs) from Wolbachia to F. exsecta. Some of these HGTs have also occurred in parallel in multiple other insect genomes, highlighting the extent of HGTs in eukaryotes. We expect that the F. exsecta genome will be valuable resource in further exploration of the molecular basis of the evolution of social organization.

genomics↗

bioRxiv2018

Degenerative expansion of a young supergene

Suppressed recombination ultimately leads to gene loss, as demonstrated by the depauperate Y chromosomes of long-established XY pairs. To understand the shorter term effects, we used high-resolution optical mapping and k-mer distribution analysis on a young non-recombining region of fire ant social chromosomes. Instead of shrinking, the region has increased in length by more than 30%. This demonstrates that degenerative expansion can occur during the early evolution of non-recombining regions.

evolutionary biology↗