| 1. |
- Ecke, Frauke, et al.
(författare)
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Landscape-based prediction of the occurrence of the invasive muskrat (Ondatra zibethicus)
- 2014
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450. ; 51, s. 325-334
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Tidskriftsartikel (refereegranskat)abstract
- In Europe, muskrat is an invasive species that can profoundly affect lake ecosystems. We developed a landscape-based prediction model for the occurrence of muskrat based on 237 muskrat and 236 randomly selected lakes within the distribution range of muskrat in northern Sweden. We analyzed the importance of slope and cover of vegetation types for the occurrence of the muskrat at 12 spatial scales (50-1000 m) from the lakeshores. Logistic regression models that incorporated slope and percentage cover of swamps, meadows and lakeshore meadows successfully predicted the occurrence of muskrat. The importance of the predictor variables changed with increased distance from the shoreline. Our results were confirmed with an independent data set (n = 29) from the southern distribution range of the muskrat in Sweden. The prediction model can be used to assess the risk of muskrat occurrence in lakes as well as for the development of muskrat-related conservation measures.
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| 2. |
- Elmhagen, Bodil, 1973-, et al.
(författare)
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Changes in vole and lemming fluctuations in northern Sweden 1960-2008 revealed by fox dynamics
- 2011
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450. ; 48:3, s. 167-179
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic dynamics with extensive spatial synchrony has long been regarded as characteristic of key herbivores at high latitudes. This contrasts to recent reports of fading cycles in arvicoline rodents in boreal and alpine Fennoscandia. We investigate the spatio-temporal dynamics of boreal red fox and alpine arctic fox in Sweden as a proxy for the dynamics of their main prey, voles and Norwegian lemming, respectively. We analyse data from five decades, 1960-2008, with wavelets and autocorrelation approaches. Cyclic dynamics were identified with at least one method in all populations (arctic fox n = 3, red fox n = 6). The dynamics were synchronous between populations, or coupled with a 1-yr lag, in 8 of 13 pairwise comparisons. Importantly though, the dynamics were heterogeneous in space and time. All analytical approaches identified fading cycles in the three arctic fox populations and two northern red fox populations. At least one method identified similar patterns in three southern red fox populations. Red fox dynamics were cyclic in the 1970s primarily, while arctic fox dynamics was cyclic until the late 1980s or early 1990s. When cyclic, 4-yr cycles dominated in arctic fox and northern red fox, whilst 3-4-yr cycles was found in southern red foxes. Significant cyclic regimes reappeared in the 1990s or 2000s in two red fox populations and one arctic fox population. Cycles and regionally coupled dynamics appeared associated in northern arctic and red foxes. This study supports accumulating evidence which suggests that cyclic and synchronous patterns in the dynamics of lemmings and voles are nonstationary in space and time. Furthermore, the similar patterns of change in both fox species indicate that persistence of cycles is governed by similar mechanisms in lemmings and voles.
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| 3. |
- Gibb, Heloise, et al.
(författare)
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Forest succession and harvesting of hemipteran honeydew by boreal ants
- 2010
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450. ; 47, s. 99-110
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Tidskriftsartikel (refereegranskat)abstract
- Ants are important harvesters of plant-derived sugars, but little is known about how anthropogenic disturbances influence this behaviour. We investigated factors related to honeydew harvesting by red wood ants, Formica aquilonia, in managed boreal forests. Ant activity was lowest in middle-age stands (30-40 years old), which had the fewest and smallest ant mounds. It was best predicted by a model containing an interaction among tree species, basal diameter and stand age. Individual workers collected similar masses of honeydew from the different aged stands, which suggests that colonies optimise foraging efforts by adjusting the number of active foragers to match resource availability. The rate of honeydew harvesting from recently clear-cut stands during the survey was similar to that in old stands, although significantly faster than in middle-aged stands. This may be a result of high aphid loads on clear-cuts and recent changes in forest management that improve the temporal continuity of forests for red wood ants. Anthropogenic alteration of habitats thus significantly alters energy use by ants, mainly as a result of changes in the abundance and size of ant colonies. This change is likely to have further consequences for ant-driven ecosystem functions.
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| 4. |
- Gustafson, Daniel, et al.
(författare)
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Terrestrial habitat predicts use of aquatic habitat for breeding purposes - a study on the great crested newt (Triturus cristatus)
- 2011
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450. ; 48, s. 295-307
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Tidskriftsartikel (refereegranskat)abstract
- This study examines the structure and composition of landscapes surrounding ponds with and without great crested newts (Triturus cristatus) - a species that needs an aquatic and a terrestrial environment. We related presence and absence data to 31 local and landscape variables, in a total of 143 areas in south-central Sweden. Land-use variables were measured within the radii of 100 m (local scale) and 500 m (landscape scale) surrounding the ponds. To find drivers of the distribution of great crested newts we used a principal component analysis (PCA) and a logistic regression analysis. Higher amounts of deciduous forest and pasture, together with proximity to deciduous forest seem to be positive for presence of great crested newts. Coniferous forest and mire appear to have a negative effect on the habitat quality for the species. We argue that management of the great crested newt should to a greater extent include the terrestrial habitat. Special attention should also be given to identifying and securing older, deciduous-rich forest in the vicinity of breeding ponds.
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| 5. |
- Milbrink, Göran, et al.
(författare)
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Rapid growth response of the Arctic charr to changing environmental conditions is not the result of a population bottleneck
- 2013
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Ingår i: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 50:6, s. 385-389
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Tidskriftsartikel (refereegranskat)abstract
- We tested if within-lake differences in individual growth in an Arctic charr population before and after nutrient enrichment was due to a population bottleneck, for example as a result of strong selection for growth in a limited part of the population. The positive change in growth pattern after treatment was not coincident with a reduction in microsatellite variability, and various genetic estimators of demographic change did not indicate changes in population size. This suggests that the change in growth was not a result of only a limited part of the population responding, but an overall response.
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| 6. |
- Rautio, Pasi, et al.
(författare)
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Food selection by herbivores and neighbourhood effects in the evolution of plant defences
- 2012
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450. ; 49:1-2, s. 45-57
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Tidskriftsartikel (refereegranskat)abstract
- A number of studies have reported how neighbouring plants may influence herbivory on palatable or unpalatable plants. Such neighbourhood effects can have important evolutionary consequences as they may either promote the evolutionary stability of plant defences or, alternatively, select against the fixation of plant defences and instead promote a stable polymorphism of palatable and unpalatable plants. These consequences depend on whether the difference in herbivore damage between unpalatable and palatable plants is smaller or, alternatively, greater when the neighbours are unpalatable instead of palatable. Such relations can arise when the neighbourhood effects are non-parallel among palatable and unpalatable plants. We outline two basic situations of non-parallel neighbourhood effects and illustrate how they can come about. A detailed dissection of these interactions reveals that there are several qualitatively distinct mechanisms that promote either evolutionary stability of plant defences or alternatively polymorphism. Our classification of mechanisms can be used to clarify and explain observations obtained in the field of plant herbivore interactions and predator prey interactions, both at the population and the community level.
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| 7. |
- Taylor, Alexandra K., et al.
(författare)
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Effects of trap density and duration on vole abundance indices
- 2011
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Ingår i: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 48:1, s. 45-55
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to investigate if patterns of immigration by voles into removal plots on the third day of trapping are evident in the grey-sided vole, and if altering the number of traps at each station will result in increased precision of the vole abundance estimate. Traps were placed using the small quadrat method, with one, three, or five traps placed at each corner. Traps were checked twice a day for five days. Mixed-effect models were used to investigate the relationship between the number of traps and the length of time the traps were out on the abundance index. There was no difference between having three or five traps. Having one trap resulted in an inflated estimate. Five traps had the highest number of successful trapping events, reducing the number of zeros in the data set and leaving fewer individuals unaccounted. There was a peak in catches on the third day, driven by younger individuals and by males. These are suspected immigrants that are exploiting the territories left by individuals trapped in the first two days, suggesting this is not a closed system.
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| 8. |
- van den Brink, Valentijn, et al.
(författare)
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Morphometric shape analysis using learning vector quantization neural networks : an example distinguishing two microtine vole species
- 2011
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Ingår i: Annales Zoologici Fennici. - 0003-455X .- 1797-2450. ; 48:6, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- Closely related species may be very difficult to distinguish morphologically, yet sometimes morphology is the only reasonable possibility for taxonomic classification. Here we present learning-vector-quantization artificial neural networks as a powerful tool to classify specimens on the basis of geometric morphometric shape measurements. As an example, we trained a neural network to distinguish between field and root voles from Procrustes transformed landmark coordinates on the dorsal side of the skull, which is so similar in these two species that the human eye cannot make this distinction. Properly trained neural networks misclassified only 3% of specimens. Therefore, we conclude that the capacity of learning vector quantization neural networks to analyse spatial coordinates is a powerful tool among the range of pattern recognition procedures that is available to employ the information content of geometric morphometrics.
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| 9. |
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