| 1. |
- Frainer, André
(författare)
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Divergence and parallelism of parasite infections in Arctic charr morphs from deep and shallow lake habitats
- 2016
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 783, s. 131-143
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Tidskriftsartikel (refereegranskat)abstract
- Parasite communities can show large differences in species composition between sympatric host species. Here, we assessed how divergent resource use of polymorphic populations of Arctic charr from two environmentally similar sub-arctic lakes was related to parasite community composition. Large similarities in parasite infections were found for both the reproductively isolated littoral-spawning omnivore LO-morph and the profundal-spawning benthivore PB-morph, reflecting cross-lake similarities in resource use. Furthermore, whereas the PB-morph had the lowest richness and abundance of parasite species in both lakes, a third morph, the profundal-spawning piscivorous PP-morph (one lake only), had the highest parasite richness and accumulated parasites by preying upon fish. These results highlight that host ecology and abiotic factors are important for structuring parasite communities. The dissimilarities in the local parasite species pool between the lakes suggest that stochastic events as well as transmission abilities are involved in structuring the parasite communities. The parallel divergent parasite infections between morphs may form an arena for parasite-mediated selection promoting the incipient speciation process in concert with other factors. The deep-water PB-morphs may avoid parasites by specialising in parasite-poor but low-productive habitats, while the piscivorous PP-morph aggregates infections of detrimental parasites through specialising on energetically rich but generally more heavily parasitised prey.
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| 2. |
- Frainer, André
(författare)
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Effects of fish species composition on Diphyllobothrium spp. infections in brown trout - is three-spined stickleback a key species?
- 2016
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Ingår i: Journal of Fish Diseases. - : Wiley. - 0140-7775 .- 1365-2761. ; 39, s. 1313-1323
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Tidskriftsartikel (refereegranskat)abstract
- Subarctic populations of brown trout (Salmo trutta) are often heavily infected with cestodes of the genus Diphyllobothrium, assumedly because of their piscivorous behaviour. This study explores possible associations between availability of fish prey and Diphyllobothrium spp. infections in lacustrine trout populations. Trout in (i) allopatry (group T); (ii) sympatry with Arctic charr (Salvelinus alpinus) (group TC); and (iii) sympatry with charr and three-spined stickleback (Gasterosteus aculeatus) (group TCS) were contrasted. Mean abundance and intensity of Diphyllobothrium spp. were higher in group TCS compared to groups TC and T. Prevalence, however, was similarly higher in groups TCS and TC compared to group T. Zero-altered negative binomial modelling identified the lowest probability of infection in group T and similar probabilities of infection in groups TC and TCS, whereas the highest intensity was predicted in group TCS. The most infected trout were from the group co-occurring with stickleback (TCS), possibly due to a higher availability of fish prey. In conclusion, our study demonstrates elevated Diphyllobothrium spp. infections in lacustrine trout populations where fish prey are available and suggests that highly available and easily caught stickleback prey may play a key role in the transmission of Diphyllobothrium spp. parasite larvae.
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| 3. |
- Frainer, André, et al.
(författare)
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Stoichiometric imbalances between detritus and detritivores are related to shifts in ecosystem functioning
- 2016
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 125:6, s. 861-871
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Tidskriftsartikel (refereegranskat)abstract
- How are resource consumption and growth rates of litter-consuming detritivores affected by imbalances between consumer and litter C:N:P ratios? To address this question, we offered leaf litter as food to three aquatic detritivore species, which represent a gradient of increasing body N: P ratios: a crustacean, a caddisfly and a stonefly. The detritivores were placed in microcosms and submerged in a natural stream. Four contrasting leaf species were offered, both singly and in two-species mixtures, to obtain different levels of stoichiometric imbalance between the resources and their consumers. The results suggest that detritivore growth was constrained by N rather than C or P, even though 1) the N: P ratios of the consumers' body tissue was relatively low and 2) microbial leaf conditioning during the experiment reduced the N:P imbalance between detritivores and leaf litter. This surprisingly consistent N limitation may be a consequence of cumulative N-demand arising from the production of N-rich chitin in the exoskeletons of all three consumer species, which is lost during regular moults, in addition to N-demand for silk production by the caddisfly. These N requirements are not commonly quantified in stoichiometric analyses of arthropod consumers. There was no evidence for compensatory feeding, but when offered mixed-species litter varying in C:N:P ratios, detritivores consumed more of the litter species showing the highest N:P and lowest C:N ratio, accelerating the mass loss of the preferred leaf species in the litter mixture. These results show that imbalances in consumer-resource stoichiometry can have contrasting effects on coupled processes, highlighting a challenge in developing a mechanistic understanding of the role of stoichiometry in regulating ecosystem processes such as leaf litter decomposition.
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| 4. |
- Frainer, André
(författare)
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Variation in functional trait composition of benthic invertebrates across depths and seasons in a subarctic lake
- 2016
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Ingår i: Fundamental and Applied Limnology. - : Schweizerbart. - 1863-9135. ; 188, s. 103-112
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Tidskriftsartikel (refereegranskat)abstract
- Benthic invertebrate communities play a fundamental role in lake ecosystems, and the understanding of how those benthic communities are structured, particularly in terms of the identity and spatiotemporal distribution of their functional traits, is key to our understanding of how lake ecosystems work. In Takvatn, a subarctic lake in northern Norway, we identified the taxonomic and functional identity of the species characterizing benthic communities across three seasons and six different depths. Invertebrates were sampled using vacuum pump and Ekman grab. Despite the relative low species richness, we found large variation across depths and seasons in species functional composition using multivariate analyses. In all seasons and habitats, gathering traits were the most common feeding traits within the benthic community. The upper littoral habitat shifted from a community characterized by particle gathers and algal scrapers in spring and summer, to a community largely characterized by leaf shredders in autumn. There was also high relative occurrence of predator traits towards the deeper areas of the littoral zone, as well as in the sub-littoral and profundal habitats. The deeper habitats showed high variation in their taxonomic composition, but a stable composition of functional traits throughout all seasons. In conclusion, our study demonstrates large spatio-temporal differences in functional trait diversity and composition of the benthic invertebrates in Takvatn.
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| 5. |
- Mckie, Brendan, et al.
(författare)
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The importance of litter traits and decomposers for litter decomposition: a comparison of aquatic and terrestrial ecosystems within and across biomes
- 2016
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 30, s. 819-829
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Tidskriftsartikel (refereegranskat)abstract
- 1. Plant leaf litter comprises the major common source of energy and nutrients in forested soil and freshwater ecosystems world-wide. However, despite the similarity of physical and biochemical processes, generalizations across aquatic and terrestrial ecosystems regarding litter decomposition drivers remain elusive.2. We re-analysed data from a published field decomposition experiment conducted in two ecosystems (forest floors and streams) across five biomes (from the tropics to subarctic) with increasing decomposer community complexity (microbes, microbes and mesofauna, microbes and meso- and macrofauna).3. Using a wide litter quality gradient (15 litter combinations), we aimed to disentangle the roles of decomposer community complexity from that of leaf litter traits (18 traits encompassing four broad trait categories: nutrients, C quality, physical structure and stoichiometry) on litter C and N loss. Comparisons of decomposition drivers between ecosystems were evaluated across and within biomes.4. Differences in environmental conditions (e.g. climate, soil/water fertility) and litter nutrients - with a particular focus on Mg and Ca - across biomes were the major drivers of litter C loss in both ecosystems, but decomposer complexity also played a prominent role in streams. Within biomes, we observed consistent effects of litter nutrients and stoichiometry on litter C and N loss between ecosystems, but the effects of decomposer complexity differed between streams and forest floors in the temperate, Mediterranean and tropical biomes.5. Our results highlight that, beyond the litter traits commonly identified as controlling decomposition (e.g. C, N and lignin), micronutrients (e.g. Mg and Ca) can also play an important, and globally consistent, role in both aquatic and terrestrial ecosystems. In addition, in forest streams the complexity of decomposer communities had similar importance as litter traits for predicting litter C and N turnover across all five biomes.6. The identification of common drivers in our large-scale ecosystem comparison suggests a basis to develop common models across aquatic and terrestrial ecosystems for C and N dynamics during decomposition. Future modelling efforts should account for the global similarities (litter micronutrient effects) and biome-level differences (contingent decomposer effects) found between ecosystems.
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