Vedlevende insekter påvirker kolonisering og suksesjon av sopp i død ved

Insekter og sopp utgjør en stor andel av alle arter på landjorda, og leverer viktige økosystemtjenester som pollinering, karbonlagring og nedbrytning. Sopp er spesielt viktig for nedbrytning av plantemateriale, siden de kan produsere enzymer som effektivt bryter ned cellulose og lignin. Dette gjør sopp til de viktigste nedbryterne av død ved, hvilket gir grunnlag for en næringskjede med stort mangfold av vedlevende arter. Arter som lever i død ved utgjør rundt 25% av alle arter tilknyttet skog i de nordiske landene, og flertallet av de vedlevende artene er insekter og sopp. Død ved er et levested med begrenset varighet, siden de vedlevende artene nødvendigvis vil bryte ned habitatet over tid. Dette gjør spredning spesielt viktig for vedlevende arter. Vedlevende insekter sprer seg hovedsakelig ved å fly, og de kan bruke syn og lukt til å finne passende substrat. Man antar at vedlevende sopp i hovedsak sprer sporene sine med vinden, med unntak av noen få arter som lever i mutualistiske forhold med treveps, barkbiller eller ambrosiabiller. Men ved en gjennomgang av relevant litteratur (artikkel I) fant vi flere studier som indikerte at spredning med insekter kan være viktig for vedlevende sopp generelt. Mange vedlevende insekter blir tiltrukket av og besøker fruktlegemer av vedlevende sopp, og disse insektene kan bære med seg intakte soppsporer i tarmene eller på hudskjelettet. Dermed kan vedlevende insekter kanskje fungere som en alternativ spredningsmåte for sopp, som i motsetning til vindspredning er målrettet mot egnede substrat. I denne avhandlingen undersøker vi hvorvidt spredning med insekter påvirker kolonisering og suksesjon av sopp i død ved.Insects and fungi comprise a large proportion of all species in terrestrial habitats, and provide important ecosystem services such as pollination, carbon sequestration and decomposition. Fungi are especially important for decay of plant material, as their extensive enzymatic machinery enables them to efficiently decompose cellulose and lignin. Thus, fungi are the primary decomposers of wood, and fuel a very diverse food chain of species dependent on dead wood, i.e. saproxylic species. Saproxylic species comprise approximately 25% of all forestdwelling species in the Nordic countries, and the most species rich eukaryotic saproxylic taxa are fungi and insects. Dead wood is an inherently ephemeral habitat, since the saproxylic species occupying this habitat will inevitably contribute to its destruction through decomposition. This continual process of community assembly and disassembly makes dispersal especially important to saproxylic species. Saproxylic insects mostly disperse by flying, and can target suitable substrates by sight and odour. Saproxylic fungi are generally assumed to disperse by windborne spores, with the exception of a few species known to be dispersed by mutualistic wood wasps, bark beetles or ambrosia beetles. However, upon review of relevant literature, we found in paper I that several studies indicate a broader role for insect-vectored dispersal of fungal propagules. Many saproxylic insects are attracted to and visit fungal fruit bodies, and can carry viable fungal propagules internally or externally. Thus, saproxylic insects might function as an additional dispersal mode for saproxylic fungi, which unlike wind dispersal can be targeted to suitable substrates. In this thesis, we have investigated whether insect-vectored dispersal might influence community assembly and succession of fungi in dead wood

Veteran trees in decline: Stratified national monitoring of oaks in Norway

Old veteran trees function as biodiversity hotspots in both forests and open landscapes, and protecting such trees is an important measure to halt loss of biodiversity. Nevertheless, the number of veteran trees continues to decline worldwide, although estimates of this decline mainly stem from geographically restricted case studies. In Norway, veteran oak trees have received special protection since 2011 through the Norwegian Biodiversity Act, however, there is a lack of knowledge on status and trends for these trees. A national monitoring program was started in 2012, using a random, stratified sampling procedure. We use the data from the baseline survey and the first monitoring revisit to estimate the total number as well as mortality trends of veteran oaks in Norway. Further, we assess recruitment potential (in the baseline survey) and changes in variables describing ecological state such as regrowth. The monitoring area covered the geographical distribution of oaks in Norway and was divided into > 200 000 plots of 500 × 500 m. A set of 500 monitoring plots were randomly selected from two strata: High probability plots (n = 100; plots with high probability of occurrence of veteran oaks), and Low probability plots (n = 400), using existing knowledge and databases. Plots were surveyed over a five year-period (2012–2016), with 20 HighProb-plots and 80 LowProb-plots each year. All veteran oaks that were observed during the baseline survey were revisited in 2019, three to seven years after they were initially registered. Tree absence and cause of death/ change of ecological status was recorded. We estimated a total of 138 100 veteran oaks in Norway based on the baseline survey, of which 25 000 could be denoted “top quality oaks”. Based on the revisit, we estimated a loss of 7 600 veteran trees, i.e., an annual mortality rate of 1.2%. Recruitment oaks were present in most plots with veteran oaks, but recruitment into the veteran oak category is slow and unlikely to balance out the mortality rate. More precise estimates of recruitment should be prioritized in future monitoring. The estimate of 138 000 veteran oaks far exceeds the appr. 10 000 trees registered in the national database, and clearly demonstrates the need for continued mapping and monitoring to improve the foundation for a knowledge-based land management. Further, this short-term monitoring demonstrates the decline of this biodiversity hotspot and pivotal source of ecosystem functions, despite increased protection in recent years. Our results and conclusions are relevant also for veteran trees of other species than oak. Quercus Ancient tree Tree inventory Monitoring Annual decline Biodiversity hotspot Heritage treespublishedVersio

Moth species richness and diversity decline in a 30‑year time series in Norway, irrespective of species’ latitudinal range extent and habitat

Introduction Insects are reported to be in decline around the globe, but long-term datasets are rare. The causes of these trends are elusive, with changes in land use and climate among the top candidates. Yet if species traits can predict rates of population change, this can help identify underlying mechanisms. If climate change is important, for example, high-latitude species may decline as temperate species expand. Land use changes, however, may impact species that rely on certain habitats. Aims and methods We present 30 years of moth captures (comprising 97,032 individuals of 808 species) from a site in southeast Norway to test for population trends that are correlated with species traits. We use time series analyses and joint species distribution models combined with local climate and habitat data. Results and discussion Species richness declined by 8.2% per decade and total abundance appeared to decline as well (−9.4%, p = 0.14) but inter-annual variability was high. One-fifth of species declined, although 6% increased. Winter and summer weather were correlated with annual rates of abundance change for many species. Opposite to general expectation, many species responded negatively to higher summer and winter temperatures. Surprisingly, species’ northern range limits and the habitat in which their food plants grew were not strong predictors of their time trends or their responses to climatic variation. Complex and indirect effects of both land use and climate change may play a role in these declines. Implications for insect conservation Our results provide additional evidence for long-term declines in insect abundance. The multifaceted causes of population changes may limit the ability of species traits to reveal which species are most at risk.publishedVersio

Opplegg for evaluering av "Bekjempelse av fremmede skadelige organismer – tiltaksplan 2020–2025"

publishedVersio

Designing a surveillance program for early detection of alien plants and insects in Norway

Naturalized species of alien plants and animals comprise < 3% of biodiversity recorded in Norway but have had major impacts on natural ecosystems through displacement of native species. Encroachment of alien species has been especially problematic for coastal sites close to transport facilities and urban areas with high density housing. The goal of our field project was to design and test a surveillance program for early detection of alien species of vascular plants and terrestrial insects at the first phase of establishment in natural areas. In our 3-year project (2018–2020), we sampled 60 study plots in three counties in the Oslofjord region of southern Norway. Study plots (6.25 ha) were selected by two criteria: manual selection based on expert opinion (27 plots) or by random selection based on weights from a hotspot analysis of occurrence of alien species (33 plots). Vascular plants were surveyed by two experienced botanists who found a total of 239 alien species of vascular plants in 95 rounds of surveys. Insects and other invertebrates were captured with a single Malaise trap per site, with 3–4 rounds of repeated sampling. We used DNA-metabarcoding to identify invertebrates based on DNA extractions from crushed insects or from the preservative media. Over 3500 invertebrate taxa were detected in 255 rounds of sampling. We recorded 20 alien species of known risk, and 115 species that were new to Norway, including several ‘doorknocker’ species identified by previous risk assessments. We modeled the probabilities of occupancy (ψ) and detection (p) with occupancy models with repeated visits by multiple observers (vascular plants) or multiple rounds of sampling (insects). The two probabilities covaried with risk category for alien organisms and both were low for species categorized as no known or low risk (range = 0.052–0.326) but were higher for species categorized as severe risk (range = 0.318–0.651)... Arthropods · DNA-metabarcoding · Early detection · Invasive · Invertebrates · Occupancy models · Rapid response · Study design · Vascular plantsDesigning a surveillance program for early detection of alien plants and insects in NorwaypublishedVersio

Saproxylic insects influence community assembly and succession of fungi in dead wood

Insekter og sopp utgjør en stor andel av alle arter på landjorda, og leverer viktige økosystemtjenester som pollinering, karbonlagring og nedbrytning. Sopp er spesielt viktig for nedbrytning av plantemateriale, siden de kan produsere enzymer som effektivt bryter ned cellulose og lignin. Dette gjør sopp til de viktigste nedbryterne av død ved, hvilket gir grunnlag for en næringskjede med stort mangfold av vedlevende arter. Arter som lever i død ved utgjør rundt 25% av alle arter tilknyttet skog i de nordiske landene, og flertallet av de vedlevende artene er insekter og sopp. Død ved er et levested med begrenset varighet, siden de vedlevende artene nødvendigvis vil bryte ned habitatet over tid. Dette gjør spredning spesielt viktig for vedlevende arter. Vedlevende insekter sprer seg hovedsakelig ved å fly, og de kan bruke syn og lukt til å finne passende substrat. Man antar at vedlevende sopp i hovedsak sprer sporene sine med vinden, med unntak av noen få arter som lever i mutualistiske forhold med treveps, barkbiller eller ambrosiabiller. Men ved en gjennomgang av relevant litteratur (artikkel I) fant vi flere studier som indikerte at spredning med insekter kan være viktig for vedlevende sopp generelt. Mange vedlevende insekter blir tiltrukket av og besøker fruktlegemer av vedlevende sopp, og disse insektene kan bære med seg intakte soppsporer i tarmene eller på hudskjelettet. Dermed kan vedlevende insekter kanskje fungere som en alternativ spredningsmåte for sopp, som i motsetning til vindspredning er målrettet mot egnede substrat. I denne avhandlingen undersøker vi hvorvidt spredning med insekter påvirker kolonisering og suksesjon av sopp i død ved

Revealing hidden insect–fungus interactions; moderately specialized, modular and anti-nested detritivore networks

Ecological networks are composed of interacting communities that influence ecosystem structure and function. Fungi are the driving force for ecosystem processes such as decomposition and carbon sequestration in terrestrial habitats, and are strongly influenced by interactions with invertebrates. Yet, interactions in detritivore communities have rarely been considered froma network perspective. In the present study, we analyse the interaction networks between three functional guilds of fungi and insects sampled from dead wood. Using DNA metabarcoding to identify fungi, we reveal a diversity of interactions differing in specificity in the detritivore networks, involving three guilds of fungi. Plant pathogenic fungi were relatively unspecialized in their interactions with insects inhabiting dead wood, while interactions between the insects and wood-decay fungi exhibited the highest degree of specialization, which was similar to estimates for animal-mediated seed dispersal networks in previous studies. The low degree of specialization for insect symbiont fungi was unexpected. In general, the pooled insect–fungus networks were significantly more specialized, more modular and less nested than randomized networks. Thus, the detritivore networks had an unusual anti-nested structure. Future studies might corroborate whether this is a common aspect of networks based on interactions with fungi, possibly owing to their often intense competition for substrate.acceptedVersio

Jacobsen_wood2018_pool_B_S1_L001_R2_001.fastq

Raw sequence data (gzipped fastq-file) from high-throughput sequencing of wood samples. Pool B, reverse reads

Jacobsen_wood2018_pool_A_S1_L001_R2_001.fastq

Raw sequence data (gzipped fastq-file) from high-throughput sequencing of wood samples. Pool A, reverse reads

GLM data for Jacobsen et al Priority effects of early successional insects influence late successional fungi in dead wood

The Fungi data sheet includes, divided by site, presence-absence data from 2013 for the species of fungi analysed in the article (G.applanatum13, P.tremulae13 and B.citrina13), presence-absence data for the fungi registered in 2005 (S.paradoxa05, T.betulina05, C.unicolor05, T.hirsuta05, P.tremulae05), number of sampled individuals during 2002-2005 of wood-boring beetles with preference for deciduous wood in total (Wood-borers) and divided by family (wCerambycidae, wCurculionidae and wPtinidae), of fungivores with a preference for deciduous wood divided by family (fCiidae, fErotylidae, fEndomychidae, fLatridiidae, fLeiodidae, fPtinidae, fStaphylinidae and fNitidulidae), of the single species tested for the article (A.nigripenne, A.humeralis, G.quadripunctatus, G.hortensis) and average percent (0-1) remaining bark on the aspen high stump and log in 2005 (Site_bark). Additionally, site ID, x and y coordinates, habitat type (Open/Closed) and study landscape (Losby/LV) of each site is recorded. The Bark data sheet includes percent bark (0-1) remaining at each highstump and log at each site in 2005, presence-absence data of B.citrina in 2013 for each highstump and log at each site, dead wood object (snag=high stump/log), site ID, x and y coordinates, habitat type (Open/Closed) and study landscape (Losby/LV)