| 3. |
- Polvi, Lina E., et al.
(author)
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Potential and actual geomorphic complexity of restored headwater streams in northern Sweden
- 2014
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In: Geomorphology. - : Elsevier BV. - 0169-555X .- 1872-695X. ; 210, s. 98-118
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Journal article (peer-reviewed)abstract
- Stream restoration usually relies on ecological theories presuming that increased habitat heterogeneity leads to higher biodiversity. However, to test this hypothesis a quantitative metric of overall geomorphic complexity is needed. We quantified geomorphic complexity using 29 metrics over five dimensions (sediment distribution, longitudinal profile, cross section, planform, and instream wood) of headwater streams in northern Sweden. We examined reaches with four different restoration statuses after a century of timber floating (channelized, restored, demonstration restored, and unimpacted) to determine (1) whether restoration increases complexity in all dimensions, (2) whether a complexity gradient can be quantified and which metrics can serve as proxies for the gradient, and (3) levels of potential complexity based on large-scale controls (drainage area, glacial legacy sediment, valley slope, valley confinement old-growth forest/buffer zone, and beaver activity). We found a significantly higher complexity in unimpacted and demonstration restoration sites than in channelized sites in all five dimensions except the cross section (based on the two metrics quantifying variability in the cross section). Multivariate analyses were able to elucidate an apparent complexity gradient driven by three complexity metrics: longitudinal roughness, sediment sorting, and cross section chain and tape ratio. The large-scale factors of valley and channel gradient as well as median grain size, along with restoration status, drive differences in complexity composition. Restoring a reach to its potential complexity is beneficial in regions without reference systems or sufficient data to model flow and sediment processes. Unimpacted and demonstration restoration reaches displayed not only more intrareach variability than channelized reaches but also greater interreach heterogeneity in complexity composition, which supports a focus on reach-scale controls on potential complexity and a landscape-scale view on restoration. (C) 2014 Elsevier B.V. All rights reserved.
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| 4. |
- Szöllösi, E, et al.
(author)
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Determinants of distribution and prevalence of avian malaria in blue tit populations across Europe: separating host and parasite effects.
- 2011
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In: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 24, s. 2014-2024
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Journal article (peer-reviewed)abstract
- Although avian malarial parasites are globally distributed, the factors that affect the geographical distribution and local prevalence of different parasite lineages across host populations or species are still poorly understood. Based on the intense screening of avian malarial parasites in nine European blue tit populations, we studied whether distribution ranges as well as local adaptation, host specialization and phylogenetic relationships can determine the observed prevalences within populations. We found that prevalence differed consistently between parasite lineages and host populations, indicating that the transmission success of parasites is lineage specific but is partly shaped by locality-specific effects. We also found that the lineage-specific estimate of prevalence was related to the distribution range of parasites: lineages found in more host populations were generally more prevalent within these populations. Additionally, parasites with high prevalence that were also widely distributed among blue tit populations were also found to infect more host species. These findings suggest that parasites reaching high local prevalence can also realize wide distribution at a global scale that can have further consequences for host specialization. Although phylogenetic relationships among parasites did not predict prevalence, we detected a close match between a tree based on the geographic distance of the host populations and the parasite phylogenetic tree, implying that neighbouring host populations shared a related parasite fauna.
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