Search results for "KIR"
showing 10 items of 3870 documents
Climate variability and lake ecosystem responses in western Scandinavia (Norway) during the last Millennium
2017
This paper provides a high-resolution temperature reconstruction for the last Millennium from Lake Atnsjøen, SE Norway (61°52′31″N, 10°10′37″E). The sedimentary record reveals strong influence of the large-scale global climate patterns on the local climate in southern part of Eastern Norway. We reconstructed mean July air temperature using Chironomidae-based transfer function and fossil Chironomidae assemblages. The reconstruction was supported by a selection of climate-sensitive geochemical and paleoecological sedimentary proxies of terrestrial and aquatic origin, including Cladocera, pollen and macrofossils. Presented results revealed that summer temperatures were 1–2 °C warmer than the m…
Do small protected habitat patches within boreal production forests provide value for biodiversity conservation? : A systematic review protocol
2019
Background Forest harvesting is the main driver of habitat degradation and biodiversity loss in forests of the boreal zone. To mitigate harmful effects, small-scale habitats with high biodiversity values have been protected within production forests. These include woodland key habitats, and other small-scale habitat patches protected by voluntary conservation action. This article describes a protocol for a systematic review to synthesize the value of small habitat patches left within production landscapes for biodiversity. The topic for this systematic review arose from a discussion with the Finnish forestry sector and was further defined in a stakeholder workshop. Research question: Do sma…
Trophic state changes can affect the importance of methane-derived carbon in aquatic food webs
2017
Methane-derived carbon, incorporated by methane-oxidizing bacteria, has been identified as a significant source of carbon in food webs of many lakes. By measuring the stable carbon isotopic composition (δ13C values) of particulate organic matter, Chironomidae andDaphniaspp. and their resting eggs (ephippia), we show that methane-derived carbon presently plays a relevant role in the food web of hypertrophic Lake De Waay, The Netherlands. Sediment geochemistry, diatom analyses and δ13C measurements of chironomid andDaphniaremains in the lake sediments indicate that oligotrophication and re-eutrophication of the lake during the twentieth century had a strong impact on in-lake oxygen availabili…
Daphnia invest in sexual reproduction when its relative costs are reduced
2018
The timing of sex in facultatively sexual organisms is critical to fitness, due to the differing demographic consequences of sexual versus asexual reproduction. In addition to the costs of sex itself, an association of sex with the production of dormant life stages also influences the optimal use of sex, especially in environments where resting eggs are essential to survive unfavourable conditions. Here we document population dynamics and the occurrence of sexual reproduction in natural populations of Daphnia magna across their growing season. The frequency of sexually reproducing females and males increased with population density and with decreasing asexual clutch sizes. The frequency of…
Shoaling with infected conspecifics does not improve resistance to trematode infection
2018
Group‐living animals can gain protection against parasitic infections through social contacts with previously infected conspecifics (social immunization). Recent research suggests that such protective effects can be induced through visual or chemical cues released by infected individuals, resulting in anticipatory immune upregulation among group members. Here, we study cue‐induced social resistance in rainbow trout Oncorhynchus mykiss exposed to a trematode parasite, the eye‐fluke Diplostomum pseudospathaceum. We established groups of naïve individuals (receivers) that were paired with previously infected individuals (donors) at different ratios of donors to receivers and at different time …
Positive density-dependent growth supports costs sharing hypothesis and population density sensing in a manipulative parasite.
2017
SUMMARYParasites manipulate their hosts’ phenotype to increase their own fitness. Like any evolutionary adaptation, parasitic manipulations should be costly. Though it is difficult to measure costs of the manipulation directly, they can be evaluated using an indirect approach. For instance, theory suggests that as the parasite infrapopulation grows, the investment of individual parasites in host manipulation decreases, because of cost sharing. Another assumption is that in environments where manipulation does not pay off for the parasite, it can decrease its investment in the manipulation to save resources. We experimentally infected rainbow trout Oncorhynchus mykiss with the immature larva…
Variability in δ13C values between individual Daphnia ephippia: Implications for palaeo-studies
2018
The stable carbon isotope ratio (δ13 C value) of Daphnia spp. resting egg shells (ephippia) provides information on past changes in Daphnia diet. Measurements are typically performed on samples of _20 ephippia, which obscures the range of values associated with individual ephippia. Using a recently developed laser ablation-based technique, we perform multiple δ13 C analyses on individual ephippia, which show a high degree of reproducibility (standard deviations 0.1e0.5‰). We further measured δ13 C values of 13 ephippia from surface sediments of three Swiss lakes. In the well-oxygenated lake with low methane concentrations, δ13 C values are close to values typical for algae (_31.4‰) and the …
Drivers of Spruce Bark Beetle (Ips typographus) Infestations on Downed Trees after Severe Windthrow
2020
Research Highlights: Bark beetles are important agents of disturbance regimes in temperate forests, and specifically in a connected wind-bark beetle disturbance system. Large-scale windthrows trigger population growth of the European spruce bark beetle (Ips typographus L.) from endemic to epidemic levels, thereby allowing the killing of Norway spruce trees over several consecutive years. Background and Objectives: There is a lack of evidence to differentiate how outbreaks are promoted by the effects of environmental variables versus beetle preferences of trees from endemic to outbreak. However, little is known about how individual downed-tree characteristics and local conditions such as tre…
Potential Solar Radiation as a Driver for Bark Beetle Infestation on a Landscape Scale
2019
In recent decades, Norway spruce (Picea abies L. Karst.) forests of the High Tatra Mountains have suffered unprecedented tree mortality caused by European spruce bark beetle (Ips typographus L.). Analysis of the spatiotemporal pattern of bark beetle outbreaks across the landscape in consecutive years can provide new insights into the population dynamics of tree-killing insects. A bark beetle outbreak occurred in the High Tatra Mountains after a storm damaged more than 10,000 ha of forests in 2004. We combined yearly Landsat-derived bark beetle infestation spots from 2006 to 2014 and meteorological data to identify the susceptibility of forest stands to beetle infestation. We found that digi…
Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica)
2019
Hydrozoans are a conspicuous component of Antarctic benthic communitites. Recent taxonomic effort has led to a substantial increase in knowledge on the diversity of benthic hydroids from some areas of the Southern Ocean, including the Weddell Sea, the largest sea in the Antarctic region. However, the study of many hydrozoan taxa are still pending, and the diversity in this huge region is expected to be higher than currently known. In order to contribute to the knowledge of taxonomy, ecology and distribution of these cnidarians, a study of unpublished material collected by several German Antarctic expeditions aboard the RV Polarstern in the eastern sector of the Weddell Sea has been conducte…