Biology subjects

Andersson, M. N.

Publications and source records attributed to Andersson, M. N..

9 recordsLinked to original sources

bioRxiv2025

Variation in seed abundance predicts yolk fatty acid composition in a wild population of birds

Bird embryos develop inside eggs, which contain maternal substances that can shape offspring phenotype and fitness. Yolk fatty acids are a key energy source for the developing embryo, with omega-6 ({omega}-6) and omega-3 ({omega}-3) polyunsaturated fatty acids (PUFAs) obtained exclusively from the diet. Therefore, food availability during the breeding season is expected to influence yolk fatty acid composition and, consequently, embryo development and growth. However, the effects of dietary variation on yolk fatty acids remain unexplored in wild birds. We investigated inter-annual variation in yolk fatty acid composition of free-living great tits (Parus major) in relation to fluctuations in beech (Fagus sylvatica) fructification--their preferred food--across two years differing strongly in seed abundance. We hypothesized that differences in beech seed availability would alter yolk fatty acid composition between years of high and low fructification, with corresponding correlations to the fatty acid profiles of available seeds. Hence, we analyzed fatty acids from seeds of beech and two conifers (Picea abies and Pinus sylvestris), which account for most of the tree cover in the study area, and from 112 eggs collected from 107 nests over two years. Beech seeds contained higher proportions of saturated (SFA), monounsaturated (MUFA), and {omega}-3 PUFAs, and lower proportions of {omega}-6 PUFAs than conifer seeds. Correspondingly, egg yolks had more SFA, MUFA, and {omega}-3 PUFAs in the year of high beech abundance, and more {omega}-6 PUFAs in the year of low abundance. Notably, the proportion of the conifer-associated {omega}-6 PUFA pinolenic acid was 64.25 times higher in years of low compared to high beech fructification, suggesting marked inter-annual variation in yolk fatty acid composition, likely reflecting shifts in maternal diet. Future experiments need to establish causal links between diet and yolk composition and assess the fitness consequences of different seed resources for breeding females and their offspring.

zoology↗

bioRxiv2023

Complex genomic landscape of inversion polymorphism in Europe's most destructive forest pest

In many species, polymorphic inversions underlie complex phenotypic polymorphisms and facilitate local adaptation in the face of gene flow. Multiple polymorphic inversions can co-occur in a genome, but the prevalence, evolutionary significance, and limits to complexity of genomic inversion landscapes remain poorly understood. Here, we examine genome-wide variation in one of Europes most destructive forest pests, the spruce bark beetle Ips typographus, scan for polymorphic inversions, and test whether inversions are involved in key adaptations in this species. We analyzed 240 individuals from 18 populations across the species European range and, using a whole-genome resequencing approach, identified 27 polymorphic inversions covering approximately 28% of the genome. The inversions vary in size and in levels of intra-inversion recombination, are highly polymorphic across the species range, and often overlap, forming a complex genomic architecture. We test several mechanisms, including directional selection, overdominance and associative overdominance that can contribute to the maintenance of inversion polymorphisms in the genome. We show that the heterogeneous inversion landscape is likely maintained by the combined action of several evolutionary forces and that inversions are enriched in odorant receptor genes encoding key elements of recognition pathways for host plants, mates, and symbiotic fungi. Our results indicate that the genome of this major forest pest of growing social, political, and economic importance harbors one of the most complex inversion landscapes described to date posing a question about limits of genomic architecture complexity.

evolutionary biology↗

bioRxiv2022

Odorant receptor orthologues in conifer-feeding beetles display conserved responses to ecologically relevant odors

Insects are able to detect a plethora of olfactory cues using a divergent family of odorant receptors (ORs). Despite the divergent nature of this family, related species frequently express several evolutionarily conserved OR orthologues. In the largest order of insects, Coleoptera, it remains unknown whether OR orthologues have conserved or divergent functions in different species. Using HEK293 cells, we addressed this question through functional characterization of two groups of OR orthologues in three species of the Curculionidae (weevil) family, the conifer-feeding bark beetles Ips typographus L. ( Ityp) and Dendroctonus ponderosae Hopkins ( Dpon) (Scolytinae), and the pine weevil Hylobius abietis L. ( Habi; Molytinae). The ORs of H. abietis were annotated from antennal transcriptomes. Results show highly conserved response specificities, with one group of orthologues (HabiOR3/DponOR8/ItypOR6) responding exclusively to 2-phenylethanol (2-PE), and the other group (HabiOR4/DponOR9/ItypOR5) responding to angiosperm green leaf volatiles (GLVs). Both groups of orthologues belong to the coleopteran OR subfamily 2B, and share a common ancestor with OR5 in the cerambycid Megacyllene caryae, also tuned to 2-PE, suggesting a shared evolutionary history of 2-PE receptors across two beetle superfamilies. The detected compounds are ecologically relevant for conifer-feeding curculionids, and are probably linked to fitness, with GLVs being used to avoid angiosperm non-host plants, and 2-PE being important for intraspecific communication and/or playing a putative role in beetle-microbe symbioses. To our knowledge, this study is the first to reveal evolutionary conservation of OR functions across several beetle species and hence sheds new light on the functional evolution of insect ORs.

neuroscience↗

bioRxiv2021

Bark beetles locate fungal symbionts by detecting volatile fungal metabolites of host tree resin monoterpenes

Outbreaks of the Eurasian spruce bark beetle (Ips typographus) have decimated millions of hectares of conifer forests in Europe in recent years. The ability of these 3-6 mm long insects to kill mature trees over a short period has been ascribed to two main factors: (1) mass attacks on the host tree to overcome tree defenses and (2) the presence of fungal symbionts that support successful beetle development in the tree. While the role of pheromones in coordinating mass attacks has been well studied, the role of chemical communication in maintaining the fungal symbiosis is poorly understood. We previously demonstrated that I. typographus can recognize beneficial fungal symbionts of the genera Grosmannia, Endoconidiophora and Ophiostoma by their de novo synthesized volatile compounds. Here, we hypothesize that the fungal symbionts of the bark beetles might metabolize spruce resin monoterpenes of the beetles host tree, Norway spruce (Picea abies), and that the volatile products could be used as cues by beetles for locating breeding sites with beneficial symbionts. We show that Grosmannia penicillata and other fungal symbionts altered the profile of spruce bark volatiles by converting the major monoterpenes into an attractive blend of oxygenated derivatives. Bornyl acetate was metabolized to camphor, and - and {beta}-pinene to trans-4-thujanol and other oxygenated products. Other co-occurring non-beneficial fungi (Trichoderma sp.) also produce oxygenated monoterpenes, but in non-attractive ratios. Extensive electrophysiological measurements showed that the bark beetle possesses dedicated olfactory sensory neurons for oxygenated metabolites. Compounds such as camphor and trans-4-thujanol attracted beetles at specific doses in olfactory experiments, and the presence of symbiotic fungi enhanced attraction of females to pheromones. Finally, we show that colonization of fungal symbionts on spruce bark diet stimulated beetles to make tunnels into the diet. Collectively, our study suggests that the blends of oxygenated metabolites of conifer monoterpenes produced by fungal symbionts are used by bark beetles as attractive cues to find breeding or feeding sites containing their essential microbial symbionts. The oxygenated metabolites may aid beetles in assessing the presence of the fungus, the defense status of the host tree and the density of conspecifics at potential feeding and breeding sites.

ecology↗

bioRxiv2021

Ionotropic receptors in the turnip moth Agrotis segetum respond to repellent medium-chain fatty acids

BackgroundIn insects, airborne chemical signals are mainly detected by two receptor families, odorant receptors (ORs) and ionotropic receptors (IRs). Functions of ORs have been intensively investigated in Diptera and Lepidoptera, while the functions and evolution of the more ancient IR family remain largely unexplored beyond Diptera. ResultsHere, we identified a repertoire of 26 IRs from transcriptomes of female and male antennae, and ovipositors in the moth Agrotis segetum. We observed that a large clade formed by IR75p and IR75q expansions is closely related to the acid-sensing IRs identified in Diptera. We functionally assayed each of the five AsegIRs from this clade using Xenopus oocytes and found that two receptors responded to the tested ligands. AsegIR75p.1 responded to several compounds but hexanoic acid was revealed to be the primary ligand, and AsegIR75q.1 responded primarily to octanoic acid, and less so to nonanoic acid. It has been reported that the C6-C10 medium-chain fatty acids repel various insects including many drosophilids and mosquitos. Our GC-EAD recordings showed that C6-C10 medium-chain fatty acids elicited antennal responses of both sexes of A. segetum, while only octanoic acid had repellent effect to the moths in a behavioural assay. In addition, using fluorescence in situ hybridization, we demonstrated that the five IRs and their co-receptor AsegIR8a are not located in coeloconic sensilla as found in Drosophila, but in basiconic or trichoid sensilla. ConclusionsOur results significantly expand the current knowledge of the insect IR family. Based on the functional data in combination with phylogenetic analysis, we propose that subfunctionalization after gene duplication plays an important role in the evolution of ligand specificities of the acid-sensing IRs in Lepidoptera.

evolutionary biology↗

bioRxiv2020

Functional evolution of a bark beetle odorant receptor clade detecting monoterpenoids of different ecological origins

Insects detect odors using an array of odorant receptors (ORs), which may expand through gene duplication. How specificities evolve and new functions arise in related ORs within a species remain poorly investigated. We addressed this question by functionally characterizing ORs from the Eurasian spruce bark beetle Ips typographus, in which antennal detection and behavioral responses to pheromones, volatiles from host and non-host trees, and fungal symbionts are well described. In contrast, knowledge of OR function is restricted to two receptors detecting the pheromone compounds (S)-(-)-ipsenol (ItypOR46) and (R)-(-)-ipsdienol (ItypOR49). These receptors belong to a species-specific OR-lineage comprising seven ItypORs. To gain insight into the functional evolution of related ORs, we characterized the five remaining ORs in this clade, using Xenopus oocytes. Two receptors responded primarily to the host tree monoterpenes (+)-3-carene (ItypOR25) and p-cymene (ItypOR27). Two receptors responded to oxygenated monoterpenoids produced in relatively large amounts by the beetle-associated fungi, with ItypOR23 specific for (+)-trans-(1R,4S)-4-thujanol, and ItypOR29 responding to (+)-isopinocamphone and similar ketones. ItypOR28 responded to the pheromone E-myrcenol from the competitor Ips duplicatus. Overall, the OR responses match well with those of previously characterized olfactory sensory neuron classes except that neurons detecting E-myrcenol have not been identified. The characterized ORs are under strong purifying selection and demonstrate a shared functional property in that they all primarily respond to monoterpenoids. The variation in functional groups among OR ligands and their diverse ecological origins suggest that neofunctionalization has occurred early in the evolution of this OR-lineage following gene duplication.

molecular biology↗

bioRxiv2020

A highly contiguous genome assembly of a major forest pest, the Eurasian spruce bark beetle Ips typographus

The Eurasian spruce bark beetle (Ips typographus [L.]), is a major killer of spruce forests across the Palearctic. During epidemics, it can destroy over 100 million cubic meters of spruce trees in a single year. Here we report a 236 Mb, highly contiguous I. typographus genome assembly using PacBio long-read sequencing. The final phased assembly had a contig N50 of 6.65 Mb in 272 contigs and was predicted to contain 23,923 protein-coding genes. Comparative genomic analysis revealed expanded gene families associated with plant cell wall degradation, including pectinases, aspartyl proteases, and glycosyl hydrolases. In todays forests, increasingly stressed by global warming, this resource can assist in mitigating bark beetle outbreaks by developing novel pest control strategies. Further, this first whole-genome sequence from the genus Ips provides timely resources to address important questions about the evolutionary biology and ecology of Curculionidae, the true weevils, one of the largest animal families.

genomics↗

bioRxiv2020

Putative ligand binding sites of two functionally characterized bark beetle odorant receptors

AO_SCPLOWBSTRACTC_SCPLOWBark beetle behavior is to a large extent mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control during outbreaks. Such an approach requires information on the function of receptors and their interactions with ligands. Hence, we annotated 73 ORs from an antennal transcriptome of the spruce bark beetle Ips typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are selective for single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. We use homology modeling and molecular docking to predict their binding sites. The importance of residues Tyr84 and Thr205 in ItypOR46 in the activation by ipsenol is experimentally supported, and hydrogen bonding appears key in pheromone binding. The biological significance of the characterized ORs positions them as prime targets for pest control and use in biosensors to detect bark beetle infestations.

neuroscience↗

bioRxiv2018

Female variation in allocation of steroid hormones, antioxidants and fatty acids: a multilevel analysis in a wild passerine bird

The environment where an embryo develops can be influenced by components of maternal origin, which can shape offspring phenotypes and therefore maternal fitness. In birds that produce more than one egg per clutch, females differ in the concentration of components they allocate into the yolk along the laying sequence. However, identification of processes that shape female yolk allocation and thus offspring phenotype still remains a major challenge within evolutionary ecology. A way to increase our understanding is by acknowledging that allocation patterns can differ depending on the level of analysis, such as the population versus the among-female (within-population) level. We employed mixed models to analyze at both levels the variation in allocation along the laying sequence of four steroid hormones, three antioxidants, and four groups of fatty acids present in the egg yolks of wild great tits (Parus major). We also quantified repeatabilities for each component to study female consistency. At a population level, the concentrations/proportions of five yolk components varied along the laying sequence, implying that the developmental environment is different for offspring developing in first versus last eggs. Females varied substantially in the mean allocation of components and in their plasticity along the laying sequence. For most components, these two parameters were negatively correlated. Females were also remarkably repeatable in their allocation. Overall, our data emphasize the need to account for female variation in yolk allocation along the laying sequence at multiple levels, as variation at a population level is underpinned by different individual patterns. Our findings also highlight the importance of considering both levels of analysis in future studies investigating the causes and fitness consequences of yolk compounds. Finally, our results on female repeatability confirm that analyzing one egg per nest is a suitable way to address the consequences of yolk resource deposition for the offspring.

physiology↗