| 1. |
- Östergård, Hannah, 1969-
(författare)
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Plant-seed predator interactions – ecological and evolutionary aspects
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant-animal interactions are affected by both abundance and distribution of interacting species and the community context in which they occur. However, the relative importance of these factors is poorly known. I examined the effects of predator host range, environmental factors, host plant populations, plant traits and fruit abortion on the intensity of pre-dispersal seed predation in 46 host populations of the perennial herb Lathyrus vernus. I recorded damage by beetle pre-dispersal seed predators, mainly Apion opeticum and Bruchus atomarius with different host ranges on L. vernus as well as on two additional host plants. Local seed predator population size was mainly influenced by plant population size, current seed production and beetle population size in the previous year, but was not strongly affected by connectivity. The monophagous seed predator was less abundant and had lower densities than the oligophagous. Both predator species had a strong ability to track fluctuations in seed production; intensity of predation increased with relative increases in seed production. Oligophagous predation on L. vernus increased with the abundance of alternative hosts, but presence of L. vernus did not affect predation on alternative hosts. Abundances and trait preferences differed among three co-occurring seed predators, but were also associated with the abundance of the other species. Overall, seed predation influenced selection on flower number. I found clear indications of seed predator offence but no obvious plant defence. The pattern of fruit abortion was associated with reduced plant fitness since the seed predator had an advanced ability to locate fruits with high probability of retention. Taken together, different factors influencing abundance of the seed predator species, different preferences, and context dependent trait selection are likely to result in complex spatio-temporal variation in overall seed losses and trait selection in the common host plant.
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| 2. |
- Faticov, Maria, 1991-
(författare)
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Spatial and temporal ecology of oak-associated fungal communities
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plants host a large diversity of microorganisms, which includes fungi, bacteria and archaea. Among these, fungi are highly diverse, and known to play a vital role in plant health and in regulation of the essential ecosystem functions. Nevertheless, we still lack a comprehensive understanding of the forces structuring plant-associated fungal communities in space and time. The main aim of this thesis was to decipher the drivers of the spatial patterns and temporal dynamics of fungal communities on plants. To this aim, I focused on Quercus robur and its associated fungi. Using a combination of observational and experimental studies, I assessed i) the distribution and drivers of the above- and belowground fungal communities at the landscape scale; ii) the role of climatic and trophic factors in defining the niches of cryptic species within a pathogen complex on oak and iii) the relative importance of warming, plant genotype and their interaction in shaping oak phenology and the seasonal dynamics of the associated fungal and insect communities.I found that aboveground fungal communities were highly variable among leaves within a single tree, and that belowground fungal communities had a stronger spatial structure than aboveground fungi at the landscape scale. Yet, climate, tree phenology or the distribution of the host tree did not explain spatial patterns in the above- and belowground communities. When focusing on three cryptic powdery mildew species within a pathogen complex on oak, I demonstrated that the climatic dimension is more important than the species interaction dimension for niche differentiation of these cryptic pathogens. A field heating experiment showed strong seasonal change in the structure of the foliar fungal community, with experimental warming playing an important role in driving this change. This experiment also revealed that warming and plant genotype jointly shape plant phenology, disease levels and insect abundance across the growing season.In conclusion, my findings suggest that abiotic forces can override biotic forces in structuring spatial patterns and temporal dynamics of fungal communities associated with plants. The particularly strong impact of warmer temperatures on foliar fungi in some of my studies indicates that climate warming has the potential to structure foliar fungal communities, with important implications for plant health, interactions between plants and other organisms and ecosystem functions.
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| 3. |
- 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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