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- Gobbo, Erik, 1990-
(författare)
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Gall induction in gall wasps (Cynipidae s. lat.) : Insights from comparative genomics
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cynipidae are a family of wasps (Hymenoptera), whose larval stages develop inside plant galls, that is, abnormal plant structures formed in response to the presence of foreign organisms. Most cynipids are gall inducers and are often capable of notable levels of host manipulation. Others are inquilines, meaning they are dependent on other species for the initiation of the gall. Their larvae then develop inside the gall, often killing the original inducer and modifying the gall in the process. The biochemical mechanism of gall induction is still shrouded in mystery. In this thesis, various approaches are implemented to try to shed some light on the process. In Paper I, we used shotgun sequencing to investigate the bacterial association of larvae of different species inhabiting the bedeguar gall on roses, and showed that neither the inquiline nor the gall inducer inhabiting this gall are associated with symbiotic bacteria that are likely to be involved in gall induction, despite earlier speculations to that effect. In Paper II, I used comparative genomic analysis of a recently evolved gall inducer in the genus Synergus and three related inquilines to identify candidate genes involved in gall initiation. Specifically, I used a new method relying on genome-wide analyses to control for confounding factors, implemented in the software Bayescode. Then, I used Gene Onthology (GO) analysis to show that the candidate genes are associated with specific functions, such as “egg follicle development” and “neural development”. In paper III, we used genomic and transcriptomic data to infer the phylogeny of the family. The analysis confirmed that the phytophagous Cynipidae fall into two distinct lineages, as suggested by a recent phylogenomic analysis based on ultraconserved elements. We propose that these families be recognized as Cynipidae s. str. (oak gallers and relatives) and Diplolepididae (rose gallers and relatives). Finally, in paper IV, I applied the same methods as in Paper II to genomes of the Cynipidae s. str. to identify candidate genes associated with gall secondary structures. I inferred that these genes are often associated with GO terms relative to egg development and cell movement. In conclusion, the data presented here can provide a useful starting point for future research on cynipids.
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| 2. |
- Karlsson, Dave, 1961-
(författare)
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Charting Insect Diversity
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background: Despite Sweden's rich legacy in entomology, a significant portion of its insect fauna remains poorly studied. Addressing this and other biodiversity knowledge gaps, the Swedish government unveiled the Swedish Taxonomy Initiative (STI) in 2002, with the ambitious goal of documenting and scientifically describing all multicellular species in the country. One of the largest projects funded by STI is the Swedish Malaise Trap Project (SMTP). The SMTP project, the data resulting from it, and the analyses of that data constitute the core of the current thesis.Methods and Results: The SMTP deployed 73 Malaise traps across 55 diverse habitats from 2003 to 2009, capturing an estimated 20 million insects. The catch has been sorted to over 300 taxonomic fractions suitable for further processing by taxonomic experts. The sorted material has been studied by over 100 taxonomists, identifying 4,000 species in about 1% of the total material. A third of these were previously unrecorded in Sweden, including nearly 700 potentially new to science. The SMTP represents a significant community effort and we describe the history, organization, logistics and methodology of the SMTP project, with a focus on the lessons learned along the way and the optimized workflows that resulted in the end. The SMTP output was used to estimate the species richness and composition of the Swedish insect fauna. This included expert assessments, analysis of new species discovery rates, and statistical extrapolations from abundance and incidence data, including a novel non-parametric estimator. These methods converged on an estimate of 33,000 species, 26% of which were unknown at the inventory’s start, and 15% of which still await discovery. To improve the speed and accuracy of the analysis of Malaise trap samples, we introduced morphotype barcoding, combining manual sorting into morphospecies with individual DNA barcoding of representative specimens. Morphotype barcoding is shown to offer more accurate abundance estimates than metabarcoding. In contrast to metabarcoding, it also provides material that is directly suitable for enhancing barcode reference libraries. At the same time, it is shown to be significantly cheaper and require less consumables than megabarcoding (specimen-level barcoding of all specimens in the sample).Conclusion: The SMTP exemplifies the successful application of community science to biodiversity research, leveraging volunteer efforts alongside professional expertise, a model that has proven to be effective in gathering extensive biodiversity data. The thesis thus offers valuable insights into planning and executing large-scale biodiversity inventories. The analyses of SMTP data suggest that a significant portion of the diversity remains undiscovered or undocumented within one of Europe's most well-studied insect faunas. The thesis highlights critical taxonomic and ecological biases in our current understanding, evidenced by the predominance of Hymenoptera and Diptera species, and decomposers and parasitoids, among the newly discovered species. These findings are pivotal in reshaping our understanding of global biodiversity and the specific ecological roles of insects. The study also emphasizes the need for a more inclusive taxonomic scope in biodiversity inventories, a challenge heightened by the urgency suggested by recent reports of alarming global declines in insect populations.
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