| 1. |
- Hambäck, Peter A., et al.
(författare)
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More intraguild prey than pest species in arachnid diets may compromise biological control in apple orchards
- 2021
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 57, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the full diet of natural enemies is necessary for evaluating their role as biocontrol agents, because many enemy species do not only feed on pests but also on other natural enemies. Such intraguild predation can compromise pest control if the consumed enemies are actually better for pest control than their predators. In this study, we used gut metabarcoding to quantify diets of all common arachnid species in Swedish and Spanish apple orchards. For this purpose, we designed new primers that reduce amplification of arachnid predators while retaining high amplification of all prey groups. Results suggest that most arachnids consume a large range of putative pest species on apple but also a high proportion of other natural enemies, where the latter constitute almost a third of all prey sequences. Intraguild predation also varied between regions, with a larger content of heteropteran bugs in arachnid guts from Spanish orchards, but not between orchard types. There was also a tendency for cursorial spiders to have more intraguild prey in the gut than web spiders. Two groups that may be overlooked as important biocontrol agents in apple orchards seem to be theridiid web spiders and opilionids, where the latter had several small-bodied pest species in the gut. These results thus provide important guidance for what arachnid groups should be targets of management actions, even though additional information is needed to quantify all direct and indirect interactions occurring in the complex arthropod food webs in fruit orchards.
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| 2. |
- Orsucci, Marion, et al.
(författare)
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Competitive ability depends on mating system and ploidy level across Capsella species
- 2022
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 129:6, s. 697-708
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Tidskriftsartikel (refereegranskat)abstract
- Background and Aims: Self-fertilization is often associated with ecological traits corresponding to the ruderal strategy, and selfers are expected to be less competitive than outcrossers, either because of a colonization/competition trade-off or because of the deleterious genetic effects of selfing. Range expansion could reduce further competitive ability while polyploidy could mitigate the effects of selfing. If pollinators are not limited, individual fitness is thus expected to be higher in outcrossers than in selfers and, within selfers, in polyploids than in diploids. Although often proposed in the botanical literature and also suggested by meta-analyses, these predictions have not been directly tested yet.Methods: In order to compare fitness and the competitive ability of four Capsella species with a different mating system and ploidy level, we combined two complementary experiments. First, we carried out an experiment outdoors in north-west Greece, i.e. within the range of the obligate outcrossing species, C. grandiflora, where several life history traits were measured under two different disturbance treatments, weeded plots vs. unweeded plots. To better control competition and to remove potential effects of local adaptation of the outcrosser, we also performed a similar competition experiment but under growth chamber conditions.Key Results: In the outdoor experiment, disturbance of the environment did not affect the phenotype in any of the four species. For most traits, the obligate outcrossing species performed better than all selfing species. In contrast, polyploids did not survive or reproduce better than diploids. Under controlled conditions, as in the field experiment, the outcrosser had a higher fitness than selfing species and was less affected by competition. Finally, contrary to the outdoor experiment where the two behaved identically, polyploid selfers were less affected by competition than diploid selfes.Conclusions: In the Capsella genus, selfing induces lower fitness than outcrossing and can also reduce competitive ability. The effect of polyploidy is, however, unclear. These results highlight the possible roles of ecological context in the evolution of selfing species.
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| 3. |
- Yang, Xuyue
(författare)
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Coevolution and molecular background of species interactions in geographic mosaics
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In complex food webs, species often interact with each other indirectly through mediating species. As a result of geographic mosaic of coevolution, such interactions are often evolutionarily unstable and the traits governing the interaction sometimes vary over time. A common example is the interactions between hosts and endoparasitoids, in which the phenotypic variation has been studied in terms of both host immunity and parasitoid virulence. This thesis focuses on characterizing the genetic background underlying the coevolution between host immune response and parasitoid virulence in a host-parasitoid interaction system. For this purpose, I used Galerucella-Asecodes system, which contains three leaf beetle species (Galerucella calmariensis, G. pusilla and G. tenella) and their shared parasitic wasp, Asecodes parviclava as the study model. By integrating next generation sequencing techniques and ab initio evidence-driven annotation approach, I generated genome assemblies and annotation of both the wasp and the three Galerucella species (Paper I & IV). In order to study variation in immune capacity at the expression level, I de novo assembled and annotated the transcriptome of G. pusilla and G. calmariensis, which have contrasting immunocompetence against the Asecodes wasp (Paper II). Using a time-course differential expression analysis, I investigated gene expression in parasitized larvae of G. pusilla and G. calmariensis after the wasp attack, and suggested that signaling and hematopoiesis genes play a key role in the host immunity in Galerucella against wasps (Paper II). Using comparative analysis of Galerucella species, I identified important genes and pathways under natural selection which potentially explain the divergence in their morphology and immunity (Paper III). I also focused on the geographic variation in the Asecodes wasp using population comparisons and identified several candidate regions of the genome for host adaptation. We also detected that genes involved in the inhibition of host immune systems and odorant/gustatory receptors are associated with variation in virulence (Paper IV).
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| 4. |
- Yang, Xuyue, et al.
(författare)
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Differential Expression of Immune Genes between Two Closely Related Beetle Species with Different Immunocompetence following Attack by Asecodes parvidava
- 2020
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Ingår i: Genome Biology and Evolution. - : Oxford University Press. - 1759-6653. ; 12:5, s. 522-534
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Tidskriftsartikel (refereegranskat)abstract
- Endoparasitoid wasps are important natural enemies of many insect species and are major selective forces on the host immune system. Despite increased interest in insect antiparasitoid immunity, there is sparse information on the evolutionary dynamics of biological pathways and gene regulation involved in host immune defense outside Drosophila species. We de novo assembled transcriptomes from two beetle species and used time-course differential expression analysis to investigate gene expression differences in closely related species Galerucella pusilla and G. calmariensis that are, respectively, resistant and susceptible against parasitoid infection by Asecodes paividava parasitoids. Approximately 271 million and 224 million paired-ended reads were assembled and filtered to form 52,563 and 59,781 transcripts for G. pusilla and G. calmariensis, respectively. In the whole-transcriptome level, an enrichment of functional categories related to energy production, biosynthetic process, and metabolic process was exhibited in both species. The main difference between species appears to be immune response and wound healing process mounted by G. pusilla larvae. Using reciprocal BLAST against the Drosophila melanogaster proteome, 120 and 121 immune-related genes were identified in G. pusilla and G. calmariensis, respectively. More immune genes were differentially expressed in G. pusilla than in G. calmariensis, in particular genes involved in signaling, hematopoiesis, and melanization. In contrast, only one gene was differentially expressed in G. calmariensis. Our study characterizes important genes and pathways involved in different immune functions after parasitoid infection and supports the role of signaling and hematopoiesis genes as key players in host immunity in Galerucella against parasitoid wasps.
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| 5. |
- Yang, Xuyue, et al.
(författare)
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Genome assemblies of three closely related leaf beetle species (Galerucella spp.)
- 2021
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Ingår i: G3. - : Oxford University Press (OUP). - 2160-1836. ; 11:8
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Tidskriftsartikel (refereegranskat)abstract
- Galerucella (Coleoptera: Chrysomelidae) is a leaf beetle genus that has been extensively used for ecological and evolutionary studies. It has also been used as biological control agent against invading purple loosestrife in North America, with large effects on biodiversity. Here, we report genome assembly and annotation of three closely related Galerucella species: G. calmariensis, G. pusilla, and G. tenella. The three assemblies have a genome size ranging from 460 to 588 Mbp, with N50 from 31,588 to 79,674 kbp, containing 29,202 to 40,929 scaffolds. Using an ab initio evidence-driven approach, 30,302 to 33,794 protein-coding genes were identified and functionally annotated. These draft genomes will contribute to the understanding of host-parasitoid interactions, evolutionary comparisons of leaf beetle species and future population genomics studies.
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| 6. |
- Yang, Xuyue, et al.
(författare)
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Lineage-specific targets of positive selection in three leaf beetles with different defence capacity against a parasitic wasp
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Parasitoid wasps are the major causes of mortality of many target host species therefore traits related to host immune defence are usually favored by natural selection. One powerful approach to detect functionally important genes under natural selection is through the analysis of directional selection acting upon protein-coding gene sequences across different species. Here, we investigated patterns of positive selection across three close related leaf beetle species with different immune defence capacity against a parasitoid wasp using a Bayesian approach for the McDonald–Kreitman test. Focus upon single-copy orthologs for Coleoptera, as well as candidate immune related genes, we detected positive selection on coding regions in each of the species specific linesages of three species closely related species of Galerucella beetles. Among these, more immune genes were under positive selection in the species with the greatest immunocompetence (G. pusilla) against parasitoid wasps, while almost no immune genes were under positive selection in the species with the least immunocompetence (G. calmariensis).
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| 7. |
- Yang, Xuyue, et al.
(författare)
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The genomic basis of adaptation to different host environments in a parasitoid wasp
- 2021
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Many insect species are infected by parasitic wasps in a constantly evolving network of interactions. Understanding the genetics of population differentiation in parasitic wasps is therefore important in the study of species diversity. Asecodes parviclava is a koinobiont endoparasitic wasp that exhibits large population variation in virulence when attacking host beetle species across Sweden. In this study, we sequenced, de novo assembled and annotated the entire genome of A. parviclava. Final assembly had a size = 384 Mbp, contained 11,196 scaffolds with a N50 = 302.549 kbp. Using an ab initio evidence-driven approach, 22,290 protein-coding genes were identified and functionally annotated. Using this genome we then performed a population genomic scan for selective patterns by generating whole genome re-sequencing data from individual wasps from 11 populations and using FST-based approaches. Finally, we searched specifically across sets of candidate venom and chemosensory genes, which may be the key traits leading to population differentiation. With 1% of SNPs as FST outliers, several regions of the genome appeared to be under strong selection. Specifically, candidate regions responsible for virulence variations included genes involved in the inhibition of host immune systems and odorant/gustatory receptors. Our study identified important regions and genes underlying mechanisms of host adaptations in parasitic wasps.
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