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Genetic diversity is a key part of biodiversity, threatened by human activities that lead to loss of gene flow and reduction of effective population sizes. Gene flow is a result of both landscape connectivity and demographic processes determining the number of dispersing individuals in space and time. Thus, the effect of human impact on processes determining the level of genetic diversity must be interpreted in the context of basic ecological conditions affecting survival and recruitment. When the intensity of human impact and habitat suitability correlate, the effect on genetic diversity and gene flow may be challenging to predict. We compared genetic diversity, gene flow and landscape resistance in two contrasting landscapes in Norway for the pond‐breeding amphibian Triturus cristatus: a highly human‐impacted, agricultural landscape with ecologically productive habitats, and a forested landscape with less productive habitats and lower levels of human impact. Our results show that genetic diversity was higher and gene flow lower within the forested landscape. Microclimatic moisture conditions and vegetation cover were important determinants of landscape resistance to gene flow within both landscapes. There were indications that landscape resistance was increased by minor roads in the forested landscape, which was not the case for the agricultural landscape, suggesting a higher vulnerability to human interference within the landscape matrix for the populations in less productive habitats. Our findings suggest that the effect of human impact on genetic diversity may not be straightforward but modulated by the ecological conditions underlying local demographic processes. Populations within both landscapes seem to be vulnerable to loss of genetic diversity, but due to different mechanisms. This has implications for the choice of relevant management actions, that is, increasing population stability may be more relevant within an agricultural landscape still permeable for dispersal, while conserving dispersal corridors may be more appropriate in the forested landscape, to avoid isolation and increased genetic drift. [ABSTRACT FROM AUTHOR]

Remote sensing data comprise a valuable information source for many ecological landscape studies that may be under-utilized because of an overwhelming amount of processing methods and derived variables. These complexities, combined with a scarcity of quality control studies, make the selection of appropriate remote sensed variables challenging. Quality control studies are necessary to evaluate the predictive power of remote sensing data and also to develop parsimonious models underpinned by functional variables, i.e., cause rather than solely correlation. Cause-based models yield superior model transferability across different landscapes and ecological settings. We propose two basic guidelines for conducting such quality control studies that increase transferability and predictive power. The first is to favor predictors that are causally related to the response. The second is to include additional variables controlling variation in the property of interest and testing for optimum processing method and/or scale. Here, we evaluated these principles in predicting ground vegetation cover, soil moisture and pH under challenging conditions with forest canopies hindering direct remote sensing of the ground. Our model using lidar data combined with natural resource maps explained most of the observed variation in soil pH and moisture, and somewhat less variation of ground vegetation cover. Soil pH was best predicted by topographic position, sediment type and site index (R2 = 0.90). Soil moisture was best predicted by topographic position, radiation load, sediment type and site index (R2 = 0.83). The best model for predicting ground vegetation cover was a combination of lidar-based estimates for light availability below canopy and forest type, including an interaction between these two variables (R2 = 0.65). [ABSTRACT FROM AUTHOR]

Featured Application: By using microsatellite markers, we were able to evaluate the genetic structuring and gene flow in red foxes in part of Scandinavia. This allowed us to delineate movement patterns of red foxes, which is important for wildlife management authorities regarding the spread of parasites and disease. The application of microsatellite markers illustrated a detailed time- and cost-effective method to investigate the gene flow and movement patterns compared to traditional tracking and GPS methodology. Knowledge about the dispersal and gene flow patterns in wild animals are important for our understanding of population ecology and the connectedness of populations. It is also important for management relating to disease control and the transmission of new and emerging diseases. Our study aimed to evaluate the genetic structuring among comparative samples of red foxes in a small part of Scandinavia and to estimate the gene flow and potential directionality in the movements of foxes using an optimized set of microsatellite markers. We compared genetic samples of red foxes (Vulpes vulpes) from two areas in Sweden and two areas in Norway, including red fox samples from areas where the occurrence of the cyclophyllic tapeworm Echinococcus multilocularis has been documented, and areas without known occurrence of the parasite. Our results show a high level of gene flow over considerable distances and substantiates migration from areas affected with E. multilocularis into Norway where the parasite is not yet detected. The results allow us to better understand the gene flow and directionality in the movement patterns of red foxes, which is important for wildlife management authorities regarding the spread of E. multilocularis. [ABSTRACT FROM AUTHOR]

Preserving of fish species and populations is important whether it is for exploitation or just for conservation. Management of fisheries aim to maintain fishable stocks that are attractive to anglers, and different means are performed. In this study from the River South Rena in southeastern Norway, conducted during 1991–2005, the effects of supportive stocking of hatchery reared brown trout (Salmo trutta L.) from 1996, and bag limit (BL) and catch‐release (CR) practice for the target species brown trout, from 2002, were explored. Effects of supplemental brown trout stocking was not noticeable, except from one year following a year of exceptional high number of stocked fish, actually 41% of the catches, whereas in the following years this proportion remained constant about 10%, and the catches remained high in 2003 and 2004, mainly due to increased angling success rate after BL‐CR introduction. [ABSTRACT FROM AUTHOR]

Hydroacoustic acquisition was performed by means of two different single beam systems, the Simradmodel EK15 from 2015 and the Simrad model EY-M from the 1980s to explore potential differences of fish density and target strength (TS) distribution between EK15 and EY-M-based estimates. The oligotrophic Lake Storsjøen (48 km2) with steep shores, was chosen for the survey. The pelagic fish stock is dominated by whitefish (Coregonus lavaretus L), and, recently, illegally stocked smelt (Osmerus eperlanus L), and a low proportion of Arctic charr (Salvelinus alpinus L.). The total density was estimated at two depth layers (18–32 and 32–48 m), and was quite similar for TS ≥ −56 dB: 755 and 498 fish ha−1, respectively for the EK15-based estimates and similarly 766 and 490 fish ha−1 for the EY-M estimate. Target strength distributions were similar for TS > −48 dB. The proportion of single fish detected with EK15 was negatively affected by the long pulse duration. Six acquisitions from 1986 to 2016 showed a dramatic increase of density of TS = −46 to −44 dB echoes (>10 cm) between 2013 and 2016. This was due to the growth of the introduced smelt population. [ABSTRACT FROM AUTHOR]

To study effects from natural selection acting on brown trout in a natural stream habitat compared with a hatchery environment, 3,781 single nucleotide polymorphism ( SNP) markers were analyzed in three closely related groups of brown trout ( Salmo trutta L.). Autumn (W/0+, n = 48) and consecutive spring (W/1+, n = 47) samples of brown trout individuals belonging to the same cohort and stream were retrieved using electrofishing. A third group (H/1+, n = 48) comprised hatchery-reared individuals, bred from a mixture of wild parents of the strain of the two former groups and from a neighboring stream. Pairwise analysis of FST outliers and analysis under a hierarchical model by means of ARLEQUIN software detected 421 (10.8%) candidates of selection, before multitest correction. BAYESCAN software detected 10 candidate loci, all of which were included among the ARLEQUIN candidate loci. Body length was significantly different across genotypes at 10 candidate loci in the W/0+, at 34 candidate loci in the W/1+ and at 21 candidate loci in the H/1+ group. The W/1+ sample was tested for genotype-specific body length at all loci, and significant differences were found in 10.6% of all loci, and of these, 14.2% had higher frequency of the largest genotype in the W/1+ sample than in W/0+. The corresponding proportion among the candidate loci of W/1+ was 22.7% with genotype-specific body length, and 88.2% of these had increased frequency of the largest genotype from W/0+ to W/1+, indicating a linkage between these loci and traits affecting growth and survival under this stream's environmental conditions. Bayesian structuring of all loci, and of the noncandidate loci suggested two ( K = 2), alternatively four clusters ( K = 4). This differed from the candidate SNPs, which suggested only two clusters. In both cases, the hatchery fish dominated one cluster, and body length of W/1+ fish was positively correlated with membership of one cluster both from the K = 2 and the K = 4 structure. Our analysis demonstrates profound genetic differentiation that can be linked to differential selection on a fitness-related trait (individual growth) in brown trout living under natural vs. hatchery conditions. Candidate SNP loci linked to genes affecting individual growth were identified and provide important inputs into future mapping of the genetic basis of brown trout body size selection. [ABSTRACT FROM AUTHOR]

Vendace and whitefish in Lake Osensjøen (boreal south-east Norway) were studied by means of gillnet test fishing (1976-2013) and hydro acoustic acquisition (1986-2011). Vendace increased in number between 1998 and 2009 while growth and size at maturity decreased. The relative density of whitefish decreased in the pelagic habitat, whereas growth and size remained the same. Both species exhibited varying year-class strength. Whereas strong year-classes of both species became less frequent after 1980 than before this, this seemed to change after 2000, especially for vendace. Generalised additive models suggested a strong positive relationship between July/August mean air temperature and year-class strength of both vendace and whitefish. Whitefish recruitment was also negatively affected by the new regulation regime implemented since 1981, and positively correlated with water level after hatching and by late ice off. The reason for the diverging impacts of environmental factors on the two species may be that vendace spawn in deeper waters that whitefish do. The results indicate that increasing summer temperatures benefit recruitment of both species, whereas low water level and early ice off will harm whitefish recruitment. Both trends are caused by climate warming. It may be speculated that increased density of the specialised plankton feeding vendace may affect the algal community through increased predation on herbivorous zooplankton and potentially affect the trophic state of the lake. [ABSTRACT FROM AUTHOR]

This study was conducted in Lake Savalen in southeastern Norway, focusing on genetic diversity and the structure of hatchery-reared brown trout (Salmo trutta) as compared with wild fish in the lake and in two tributaries. The genetic analysis, based on eight simple sequence repeat (SSR) markers, showed that hatchery bred single cohorts and an age structured sample of stocked and recaptured fish were genetically distinctly different from each other and from the wild fish groups. The sample of recaptured fish showed the lowest estimated effective population size Ne = 8.4, and the highest proportion of siblings, despite its origin from five different cohorts of hatchery fish, counting in total 84 parent fish. Single hatchery cohorts, originating from 13–24 parental fish, showed Ne = 10.5–19.9, suggesting that the recaptured fish descended from a narrow group of parents. BayeScan analysis indicated balancing selection at several loci. Genetic indices of wild brown trout collected in the lake in 1991 and 2010 suggested temporal genetic stability, i.e., the genetic differentiation (FST) was non-significant, although the Ne, the number of alleles per locus and the number of private alleles were lower in the 2010 sample. [ABSTRACT FROM AUTHOR]

Density estimation of pelagic fish was performed by means of single beam echosounding in 17 lakes within a period of 34 years, from 1985 to 2018. Surveys were performed repeatedly (two to fourteen times) in five lakes. The density estimates ranged from 34 to 4720 fish/ha and were significantly correlated with total phosphorus concentration. The high density in relatively phosphorus rich lakes (TP > 10 µg/L) was comprised of small fish (<20 cm) and was partly due to the higher number of pelagic fish species. The number of pelagic species varied from one, Arctic charr, in the most elevated and oligotrophic lakes, and whitefish dominated in less elevated oligotrophic lakes. In lowland lakes characterized as mesotrophic or tending to mesotrophy, smelt, vendace, and two to three cyprinids comprised the pelagic fish stock. These fish species predate zooplankton effectively, and species composition and body size of planktonic cladocerans was affected by fish density. Large species of Daphnia were lacking in lakes with high fish density, and body size of present species, D. galeata, D. cristata, and Bosmina spp. were negatively correlated with pelagic fish density. [ABSTRACT FROM AUTHOR]

A total of 312 specimens of freshwater pearl mussel (Margaritifera margaritifera) were sampled from 11 populations, located in four different river systems in Southeast Norway, and analyzed for 11 simple sequence repeat (SSR) (microsatellite) markers. All study populations have landlocked brown trout (Salmo trutta) as the only possible host. Several populations had experienced recruitment failure, probably due to low pH (about 6.0) and calcium concentration. STRUCTURE clustering analysis revealed two genetic clusters, of which one cluster occurred mainly in the western river systems, and totally dominated in one population (Fallselva (A-FAL)) that had higher genetic diversity than the others. Cluster 2 completely dominated in the populations of the eastern river systems, and all of them had low genetic diversity. Bottleneck events were indicated in all populations and the inbreeding coefficient FIS was significant in all populations, except for the southernmost population (Sørkedalselva (B-SØR)), which was the only population with genotypes in Hardy–Weinberg equilibrium. FIS were especially high in the populations of the eastern river systems, and maximum shell length was negatively correlated to FIS. If artificially breeding and stocking should become necessary for future preservation, it should be based on single populations; alternatively, the eastern populations should be based on cross-breeding of populations within the cluster to increase their genetic diversity. [ABSTRACT FROM AUTHOR]