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1. Due to globalisation, trade and transport, the spread of alien species is increasing dramatically. Some alien species become ecologically harmful by threatening native biota. This can lead to irreversible changes in local biodiversity and ecosystem functioning, and, ultimately, to biotic homogenisation. 2. We risk-assessed all alien plants, animals, fungi and algae, within certain delimitations, that are known to reproduce in Norway. Mainland Norway and the Arctic archipelago of Svalbard plus Jan Mayen were treated as separate assessment areas. Assessments followed the Generic Ecological Impact Assessment of Alien Species (GEIAA) protocol, which uses a fully quantitative set of criteria. 3. A total of 1519 species were risk-assessed, of which 1183 were species reproducing in mainland Norway. Among these, 9% were assessed to have a severe impact, 7% high impact, 7% potentially high impact, and 49% low impact, whereas 29% had no known impact. In Svalbard, 16 alien species were reproducing, one of which with a severe impact. 4. The impact assessments also covered 319 so-called door-knockers, i.e. species that are likely to establish in Norway within 50 years, and 12 regionally alien species. Of the door-knockers, 8% and 10% were assessed to have a severe and high impact, respectively. 5. The impact category of most species was driven by negative interactions with native species, transformation of threatened ecosystems, or genetic contamination. The proportion of alien species with high or severe impact varied significantly across the different pathways of introduction, taxonomic groups, time of introduction, and the environments colonised, but not across continents of origin. 6. Given the large number of alien species reproducing in Norway and the preponderance of species with low impact, it is neither realistic nor necessary to eradicate all of them. Our results can guide management authorities in two ways. First, the use of quantitative assessment criteria facilitates the prioritisation of management resources across species. Second, the background information collected for each species, such as introduction pathways, area of occupancy and ecosystems affected, helps designing appropriate management measures. 1. Globalisering, handel og transport fører til en dramatisk økning i spredningen av fremmede arter. Noen fremmede arter er skadelige og truer det stedegne naturmangfoldet. Lokalt kan dette medføre irreversible endringer i det lokale biologiske mangfoldet og økosystemenes funksjon; globalt en homogenisering av artssammensetningen. 2. Vi har gjennomført risikovurderinger av alle fremmede planter, dyr, sopper og alger som reproduserer i Norge og oppfyller visse avgrensninger. Svalbard og Jan Mayen ble behandla som et eget vurderingsområde, adskilt fra Fastlands‐Norge. Risikovurderingene ble gjort i tråd med GEIAA (Generic Ecological Impact Assessment of Alien Species), som benytter et rent kvantitativt kriteriesett. 3. Totalt ble 1519 arter risikovurdert, hvorav 1183 reproduserte i Fastlands‐Norge. Av disse ble 9 % vurdert til å utgjøre en svært høy risiko, 7 % en høy risiko, 7 % en potensielt høy risiko, 49 % en lav risiko og 29 % ingen kjent risiko. På Svalbard forekom 16 reproduserende fremmede arter, hvorav én med svært høy risiko. 4. Risikovurderingene omfatta også 319 såkalte dørstokkarter, dvs. fremmede arter som antas å kunne etablere seg i Norge innen 50 år, samt 12 regionalt fremmede arter. Blant dørstokkartene ble 8 % og 10 % vurdert til å utgjøre en svært høy respektive høy risiko. 5. For de fleste arter ble risikokategorien bestemt av artenes interaksjoner med stedegne arter, tilstandsendringer i trua naturtyper eller genetisk forurensning. Andelen av fremmede arter med høy eller svært høy risiko varierte signifikant på tvers av ulike introduksjonsveier, artsgrupper, tidspunkt for introduksjon og koloniserte naturtyper, men ikke på tvers av opphavsområder. 6. Gitt det store antallet av fremmede arter som reproduserer i Norge, og overvekten av arter som har lav risiko, er det verken realistisk eller nødvendig å utrydde alle. Resultatene våre kan hjelpe forvaltningsmyndighetene på to måter. For det første gjør bruken av kvantitative kriterier det lettere å prioritere ressurser på tvers av arter. For det andre kan passende forvaltningstiltak utarbeides på grunnlag av den innsamla bakgrunnsinformasjonen om artene, f.eks. deres spredningsveier, forekomstareal og berørte naturtyper. This is an open access article under the terms of the Creative Commons Attribution License, which permits use,distribution and reproduction in any medium, provided the original work is properly cited.c 2020 The Authors. Ecological Solutions and Evidence published by John Wiley & Sons Ltd on behalf of British Ecological Society

This is a post-peer-review, pre-copyedit version of an article published in Biological Invasions. The final authenticated version is available online at: https://doi.org/10.1007/s10530-019-02058-x. We present the results of an inventory and status assessment of alien species in Norway. The inventory covered all known multicellular neobiota, 2496 in total, 1039 of which were classified as naturalised. The latter constitute c. 3% of all species known to be stably reproducing in Norway. These figures are higher than expected from Norway’s latitude, which may be due a combination of climatic and historical factors, as well as sampling effort. Most of the naturalised neobiota were plants (71%),followed by animals (21%) and fungi (8%). The main habitat types colonised were open lowlands (79%), urban environments (52%) and woodlands (42%). The main areas of origin were Europe (67%), North America (15%) and Asia (13%). For most taxa, the rate of novel introductions seems to have been increasing during recent decades. Within Norway, the number of alien species recorded per county was negatively correlated with latitude and positively correlated with human population density. In the high-Arctic territories under Norwegian sovereignty, i.e. Svalbard and Jan Mayen, 104 alien species were recorded, of which 5 were naturalised.

We here report the first sign of amphibian recovery after a strong decline due to acidic precipitation over many decades and peaking around 1980–90. In 2010, the pH level of ponds and small lakes in two heavily acidified areas in southwestern Scandinavia (Aust-Agder and Østfold in Norway) had risen significantly at an (arithmetic) average of 0.14 since 1988–89. Parallel with the general rise in pH, amphibians (Rana temporaria, R. arvalis, Bufo bufo, Lissotriton vulgaris, and Triturus cristatus) had become significantly more common: the frequency of amphibian localities rose from 33% to 49% (n = 115), and the average number of amphibian species per locality had risen from 0.51 to 0.88. In two other (reference) areas, one with better buffering capacity (Telemark, n = 21) and the other with much less input of acidic precipitation (Nord-Trøndelag, n = 106), there were no significant changes in pH or amphibians. This is a pre-print of an article published in [Ambio]. The final authenticated version is available online at: https://link.springer.com/article/10.1007%2Fs13280-017-0988-5

Telemetry studies of newt species demand small transmitters. Two types of external attachments (sutured to epidermis and backpack) and traditional implanting in the peritoneal cavity were tested between groups of 5 adult individuals of the crested newt Triturus cristatus (mass 6-15 g) held in terrariums under controlled environmental conditions. The newts were anaesthetized with 1.5 g l–1 MS222, delivered in water and buffered to pH 6.9 by Na2CO2. Surgical plane of anaesthesia was achieved after 5-12 minutes and lasted for 30-60 minutes. External tagging proved unsuitable because transmitters became entangled in vegetation, and all animals shed their transmitters shortly after tagging, except for one that died. Transmitters that were surgically implanted in the peritoneal cavity were more successful. By the fourth day following surgery, the animals that had undergone surgery behaved similarly to control animals with respect to the use of cover. Two of the newts died, however, without showing any signs of illness in advance, and the cause of death could not be established. Based on the present experiments and published studies, implantable transmitters appear to be the best method for radiotagging small and medium sized urodele species such as T. cristatus, to gain crucial information on spatio-temporal terrestrial activity patterns, habitat utilization and hibernation sites. Additional research is needed to evaluate both short and long term effects on activity, behaviour and survival.

Larval Bufo bufo (L., 1758) and Triturus vulgaris (L., 1758) were exposed to soft water (0.5 mg·L–1 Ca2+) experimentally acidified to pH 3.9 to 5.9 and total aluminium concentrations of –1. Below pH 4.5 both species experienced increased mortality. The LC50 (168 h) for –1 Al was pH 4.3 and 4.1 for B. bufo and 4.2 and 4.1 for T. vulgaris. However, Al3+ increased the survival of both species, which may be due to the contribution of Al3+ to the ionic strength. No B. bufo larvae died at pH >4.5, whereas T. vulgaris at higher Al concentrations suffered relatively high mortality at pH 5.1–5.9, where Al occurs mainly as Al(OH)2+ and Al(OH)2+. Unlike external gills (T. vulgaris), internal gills (B. bufo) have their own internal environment and are probably better protected against the presence of these toxic Al species in the water. These Al species thus seem to be toxic to T. vulgaris larvae but not to B. bufo. Chloride was seen to be important for survival in water of low ionic strength, since the survival of T. vulgaris larvae, particularly at low Al concentration, increased at pH levels down to pH 4.3 when the water was acidified with HCl.

Amphibian populations are declining at an alarming pace in many parts of the world. Consequently, as part of the strategy for establishing a 360 km2 conservation and reference area for amphibians in central Norway, 341 lentic water bodies were surveyed to investigate and briefly describe their hydrography and the occurrence of the newts Triturus vulgaris (L.) and T. cristatus (Laurenti) in the area. In particular we investigated the factors that could explain the presence of the respective newt species, including biotic and abiotic factors. The multiple logistic regression analyses suggested that the presence of T. cristatus was best explained by altitude and ion concentration, both in a nonlinear fashion, whereas fish had a negative effect on T. cristatus, which was never found coexisting with fish. The presence of T. vulgaris was best explained by altitude (linear relationship) and ion concentration (convex relationship), besides the occurrence of T. cristatus. Triturus vulgaris was occasionally found to occur at low densities in ponds having fish. For both species the probability of presence was higher when the opposite newt species was present. pH influenced both species in a convex nonlinear fashion with highest probability of presence around pH 6.5. This area is valuable for conservation, monitoring and reference for marginal amphibian populations. Any decline in their abundance would be discovered relatively quickly, and likely causes could be inferred. It can also serve as a reference area for future comparative studies of amphibians elsewhere.

Palaemonetes varians has been recorded at 11 localities in southern Norway and one locality in Bohuslan, Sweden. Its habitat is brackish water lakes and shallow, coastal lagoons of variable salinity (0.9–25.3). In Oslofjord, lagoons are rare, and P. varians was only found at one locality, Stokke in the county of Vestfold, on the western side of the fjord. No specimens were recorded along the coast north of Stromstad, Bohuslan, which is far north of previous records in Sweden. The occurrence of P. varians in southern Norway seems to be quite isolated from its main distribution in Europe. In high and medium saline (salinity > 5) biotopes, P. varians often occurred with Palaemon elegans and/or P. adspersus, which are common in more open and turbulent biotopes along the coast. In shared localities, P. varians seemed to be competitively displaced by the larger Palaemon species into large stands of telmatophytic vegetation, and few were found in open water. At low salinities (

The diel activity of Ilybius fenestratus was studied in Malsj⊘en, a lake in S⊘r-Tr⊘ndelag, Central Norway (63°14'N, 10°26'E), during 1971–1972. Adults and larvae were sampled in activity traps every week during March–October and every 2–3 weeks during November–February. The traps were emptied every 2 hrs during a 24- hr period. The diel locomotor activity of I. fenestratus was clearly nocturnal, except in the second half of July, for the males also in the first half of July, when surprisingly the population showed an arrhythmic activity pattern. The arrhythmicity is connected with the mating and egg-laying period of the species. The larvae were also nocturnal in the autumn, but showed arrhythmicity under the ice during the winter.

The life history of Ilybius fenestratus was studied in Malsj⊘en, a lake in S⊘r-Tr⊘ndelag, Central Norway (63°14'N, 10°26'E), during 1971–1972. Adults and larvae were sampled in activity traps every week during March–October and every 2–3 weeks during November–February. Newly-emerged adults were generally found from mid-July to September, and after overwintering in torpidity, probably in the water, they again appeared in the second half of June to August/September. Laying of eggs took place from early/mid July to early August. Larvae occurred in the traps from late July to early May. I. fenestratus was thus found to be a semivoltine summer breeder, with overwintering larvae the first winter and overwintering adults the next. Both adults and larvae lived in large areas of the lake's littoral zone.

Dolmen D and Kleiven E. 2008. Distribution, status and threats of the freshwater pearl mussel Margaritifera margaritifera (Linnaeus) (Bivalvia, Margaritiferidae) in Norway. Fauna norvegica 26/27: 3-14. The distribution of Margaritifera margaritifera (Linnaeus) in Norway is mainly along the coast and in the lowland. Based on a questionnaire sent to county governors’ offices and municipal administrations in Norway, about 430 former and existing localities have been recorded, of which about 300 are still-existing. However, the real number is probably more than twice as large. Central Norway has the highest number of documented sites. The northernmost locality is at Berlevag (Finnmark) at 70°50’N lat., and the highest verified record is near Snasa (Central Norway) at 472 m a.s.l. The great majority of localities are associated with Cambro-Silurian volcano-sedimentary rocks or situated below the postglacial marine limit, i.e. in areas not too poor in calcium. The species is an early immigrant, and a landlocked population in Central Norway has probably existed since 8900 14 C-yr B.P. The pearl mussel has become extinct during the past few decades at as many as 30% of its localities, mostly due to urbanisation and pollution. There is a high correlation between the density of people in a county (or the proportion of cultivated land) and the “density” of extinct pearl mussel populations (r=0.91). Other threats considered were hydropower regulations, excavations and constructional work in the watercourse, fishing for pearls, acidification and natural droughts or floods. In spite of the negative trend, some large populations still exist, with local densities >100 ind. m -2 and numbers of up to 1 mill. ind. km -1 river stretch. The Norwegian stock probably consists of >300 mill. ind.

The first record for many decades of the brackish-water prawn Palaemonetes varians is reported from Norway. The species was observed in June and July 1992 in great numbers in three permanent brackishwater lakes at Grimstad, Aust-Agder in southern Norway. Since the brackish nature of these lakes is only about 120 years old, the local prawn population must be relatively young, and the species is therefore probably also present in neighbouring estuaries.

The growth and size of the newts, Triturus vulgaris (L.) and T. cristatus (Laurenti) in different parts of Norway (+ Jamtland, Sweden) were studied. Age was estimated from skeletal growth marks, size-frequency histograms and, for the males, from the number of testis lobes. On average, the T. vulgaris Larvae in central Norway and Jamtland are smaller than those in southeastern Norway, although in good localities, at the same altitude, they are of approximately the same size and complete their development already within 2½–3 months. Larvae living in eutrophic habitats are larger than those in oligotrophic-dystrophic habitats. In bog habitats at similar times of year the T. cristatus larvae from central Norway are about the same size as those from similar habitats in southwestern and southeastern Norway, but somewhat smaller than those from eutrophic ponds in the Oslofjord area. No significant differences in the mean size of adult T. vulgaris from southeastern Norway and from central Norway were found. The maximum lengths attained were recorded from central Norway, however. In eutrophic habitats T. vulgaris adults BK usually larger than those in oligotrophic/dystrophic habitats. In southeastern Norway, where growth is rapid, T. vulgaris may become sexually mature when 2+ yr-old, in central Norway usually a year later, in Jamtland. on average, still later, and in their northernmost locality (Vefsn) they probably do not breed until 5+ or 6+ yr-old. On average, T. cristatus adults from southeastern Norway are slightly larger than those from central Norway, and may become mature at 2+ yr-old. compared with 4 + yr-old, at the earliest, in the latter area. The differences in the growth rates of both larvae and metamorphosed stages, of both species, most probably represent a response to climatic differences, although biotope quality is also an important factor.

Two methods of age determination in newts. Triturus vulgaris and T. cristatus, have been examined and compared: (1) Counting growth rings in the bone tissue of humerus or femur is an accurate method, but possible supplementary rings may make the reading difficult. The innermost periosteal zone corresponds to the first year of life. Later, new zones are added each year. (2) Every second year after maturing a new lobe is developed on the testes. Knowing the juvenile life span in a population, it is possible to determine the age of male newts with a possible error of one year. The correlation between growth marks and testis lobes in T. vulgaris and T. cristatus is highly significant. The testis lobing method, however, is less applicable in older newts, since no more than three or four lobes can be developed on a testis.

The diets oftwo sympatric species of newts, Triturus vulgaris(L.) and T. cristatus(LAURENTI), from two localities in central Norway, have been compared. Adult T. vulgaris ate mainly those Cladocera which can be classified as planktonic, and to a lesser degree those which are predominantly benthic. The food of T. cristatus was predominantly benthic invertebrates and Cladocera associated with the bottom. T. vulgaris larvae ate planktonic - and predominantly benthic Cladocera, and to a certain degree also larger benthic invertebrates, while T. cristatus larvae (July-August) had taken almost exclusively Cladocera, 75% of which can be classified as planktonic. Large T. cristatus larvae (in September) had eaten relatively more benthic prey. These data would fit the hypothesis that the modes of feeding of the species are different: Adult T. vulgaris swim about in the water much of the time, while T. cristatus stay on the bottom. Among the young, T. vulgaris larvae are mainly associated with the bottom, while T. cristatus larvae are definitely more nektonic during most of the summer; large T. cristatus larvae, however, when nearing the time for metamorphosis, become benthic.

The newts Triturus vulgaris and T. cristatus are sympatric over almost the whole of their distributional areas, and they very often share the same breeding-ponds. According to "the competitive exclusion principle", however, no two species occupying the same ecological niche can persist together. Accordingly, within their habitat, the niches of the newts should be different. Studies on their macro- and microhabitat, diel activity, terrestrial seasonality and food, both of adults and larvae, indeed reveal such differences, especially in terrestrial seasonality, microhabitat and food preference. Although the habitat requirements of these newts are much the same, there is a clear resource partitioning between them, and adult T. cristatus also tends to exhibit a narrower niche breadth than does T.vulgaris.

The diel activity and microhabitat preference of Triturus vulgaris and T. cristatus were studied outdoors in central Norway during summer (adults) and autumn (larvae) using aquaria and photocell equipment. Although aquatic adult newts in high latitudes are generally crepuscular or nocturnal animals, they also exhibit diurnal activity, especially the males. Larvae are normally diurnal, but metamorphosing T. vulgaris larvae showed only slight rhythmic activity. T. cristatus larvae exhibited a phase shift to nocturnal activity in late autumn. The exact time for peak activity during day and night is not only dependent on the 24 h light/dark cycle, but also on the light/ temperature conditions throughout the day. Aquatic adults of T. cristatus are mainly bottom living, while adult T. vulgaris spend much of their time in the open water. The larvae show an opposite pattern. This microhabitat specialization probably helps to reduce competition for food, and also reduces cannibalism.