Arild Johnsen

Utvalgte publikasjoner

• Klemetsen, Terje; Endresen, Dag; Johnsen, Arild; Boer, Hugo de; Fossøy, Frode & Ekrem, Torbjørn [Vis alle 11 forfattere av denne artikkelen] (2026). Strengthening molecular biodiversity research and monitoring in Norway – connecting tools, data and people. F1000 Research. 15, s. (ELIXIR)–(ELIXIR). doi: 10.12688/f1000research.179210.1. Fulltekst i vitenarkiv Vis sammendrag

  Background Norway’s diverse ecosystems and strong research community are well-positioned to leverage molecular approaches (DNA barcoding, eDNA, whole-genome sequencing) for biodiversity research and monitoring. However, progress is constrained by gaps in data accessibility, standardisation, and interoperability across molecular, ecological, and biobank datasets. Methods ELIXIR’s Norwegian Molecular Biodiversity Working Group mapped national actors and networks through a desk review (2024–2025) and conducted a national survey (58 questions; open from 18 February to 8 March 2024) targeting data management, standards, tooling, infrastructures, and training. The survey was implemented in Nettskjema and received 58 responses from biodiversity-related researchers. Results We identified 19 Norwegian institutes active in molecular biodiversity and 28 relevant networks, with 11 networks involving three or more institutes. The survey results highlight gaps between policy and practice: 60% of respondents were familiar with the FAIR principles, but only 29% consistently made data fully open or FAIR-compliant. Data linkage with physical specimens was often reported as missing (38% of respondents), and taxonomic assignment was frequently challenging (39.3%). Most researchers reuse published datasets (90%), but data discovery and reuse are hindered: only 41% find it easy to locate relevant data, 32% struggle to find appropriate sequence databases, 54% cite insufficient metadata, and 72% need to harmonise combined datasets. Tool discoverability and documentation were limited (32% knew bio.tools; 5% WorkflowHub; 32% agreed tools are well documented and user-friendly). Data publication is not straightforward (63.8% find it hard or answered neutral). Conclusions Norway can strengthen molecular biodiversity research by 1) connecting molecular and ecological data, collections, and biobanks using persistent identifiers; 2) adhering to international metadata standards (e.g., DwC, MIxS) and rewarding data stewardship; 3) consolidating national collaborative networks; and 4) building capacity through targeted training and dedicated data steward roles. Implementing these measures will enhance interoperability, FAIR data sharing, and Norway’s leadership in biodiversity research and conservation.

• Øksnebjerg, Daniel Bilyeli; Nielsen, Sascha Dreyer; Chen, Guangji; Andersen, Michael J.; Almagro, Vanessa & Ambrosini, Roberto [Vis alle 93 forfattere av denne artikkelen] (2026). A comprehensive reference genome assembly dataset of birds inhabiting Denmark, Greenland, and the Faroe Islands. GigaScience. 15, s. 1–9. doi: 10.1093/gigascience/giag078.
• Chen, Guangji; Wang, Shuang; Bilyeli Øksnebjerg, Daniel; Nielsen, Sascha Dreyer; Dai, Wei & Jiang, Wei [Vis alle 69 forfattere av denne artikkelen] (2026). Draft assemblies for 177 bird species enhance genus-level coverage. GigaScience. 15. doi: 10.1093/gigascience/giag045. Fulltekst i vitenarkiv
• Cramer, Becky; Chen, Kuei‐Chiu & Johnsen, Arild (2025). Overwintering and Resident Birds in Qatar: Explorations With DNA Barcoding. Ecology and Evolution. 15(7). doi: 10.1002/ece3.71817. Fulltekst i vitenarkiv Vis sammendrag

  Genetic research is unevenly distributed across the globe, with most research done in temperate zones. To better understand the birdlife in an under‐represented, arid subtropical country, Qatar, we blood sampled birds and salvaged tissue from dead birds, then sequenced a mitochondrial marker (cytochrome c oxidase subunit I, COI, the “DNA barcoding” gene). We chose the DNA barcoding gene because it has previously proven useful for preliminary explorations of evolutionary history. We obtained DNA barcodes for 115 birds (34 species, 12 orders). Our data suggest that the existing DNA barcode reference library, built largely from sampling in the Americas, Europe, and east Asia, is generally sufficient for species identification in Qatar. Based on DNA barcode similarity, Qatar provides overwintering habitat to some species with apparent strong migratory connectivity and others with weaker migratory connectivity. Among locally breeding species, we found no evidence of hybridization between House Sparrows Passer domesticus ( n  = 16 males) and Spanish Sparrows P. hispaniolensis ( n  = 14 males), breeding simultaneously and in the same habitats, although in other locations of range overlap, habitat segregation and timing of breeding are hypothesized to be the primary reproductive barrier between them. Our results highlight the benefits of expanding the geographic range of genetic and ecological research.

• Koppetsch, Thore; Bagdonaite, Laima; Capucho, Ana Teresa; Tveit, Bjørn Olav & Johnsen, Arild (2025). First genetically confirmed record of a wild Marsh Tit × Willow Tit hybrid (Poecile palustris × P. montanus). Journal of Ornithology. ISSN 2193-7192. doi: 10.1007/s10336-025-02317-w. Fulltekst i vitenarkiv Vis sammendrag

  Die Identifizierung unauffälliger Hybriden im Freiland ist oft problematisch und kann bei Arten, die sich phänotypisch ähneln, zu einer niedrigen Nachweisrate führen. Hier präsentieren wir den Nachweis eines Hybrids zwischen der Sumpfmeise ( Poecile palustris ) und der Weidenmeise ( P. montanus ) aus Südnorwegen, der anhand von Fotomaterial, Tonaufnahmen und molekularen Analysen verifiziert wurde. Dieser integrative Ansatz ermöglichte die Geschlechtsbestimmung des Hybridindividuums nebst Identifizierung beider Elternspezies. Unser Nachweis stellt den ersten genetisch bestätigten Fund einer Hybridisierung zwischen diesen beiden Arten in der freien Natur dar.

• Bagdonaite, Laima; Leder, Erica Helen; Lifjeld, Jan Terje; Johnsen, Arild & Mauvisseau, Quentin (2025). Assessing reliability and accuracy of qPCR, dPCR and ddPCR for estimating mitochondrial DNA copy number in songbird blood and sperm cells. PeerJ. 13. doi: 10.7717/peerj.19278. Fulltekst i vitenarkiv Vis sammendrag

  Mitochondrial DNA (mtDNA) copy number varies across species, individuals, and cell types. In birds, there are two types of cells with a relatively low number of mitochondria: red blood cells and spermatozoa. Previous studies investigating variation of mitochondrial abundance in animal sperm have generally used quantitative PCR (qPCR), but this method shows potential limitations when quantifying targets at low abundance. To mitigate such issues, we investigated and compared the reliability and accuracy of qPCR, digital PCR (dPCR) and droplet digital PCR (ddPCR) to quantify high and low concentration DNA. We used synthetic DNA targets, to calculate the limit of detection and the limit of quantification and found that with both dPCR and ddPCR, these limits were lower than with qPCR. Then, to compare quantification accuracy and repeatability, we used DNA extracted from blood and sperm cells of Eurasian siskin. We found that qPCR, dPCR and ddPCR all reliably quantified mitochondrial DNA in sperm samples but showed significant differences when analyzing the typically lower levels of mtDNA in blood, with ddPCR consistently showing lower variation among replicates. Our study provides critical insights and recommendations for future studies aiming to quantify target mtDNA and indicates that dPCR and ddPCR are the preferred methods when working with samples with low abundance of mtDNA.

• Bagdonaite, Laima; Mauvisseau, Quentin; Johnsen, Arild; Lifjeld, Jan Terje & Leder, Erica Helen (2025). Sperm mtDNA Copy Number Is Not Associated With Midpiece Size Among Songbirds. Ecology and Evolution. 15(3). doi: 10.1002/ece3.71055. Fulltekst i vitenarkiv Vis sammendrag

  Tremendous variation in sperm morphology is observed across the animal kingdom. Within avian taxa, the songbirds (infraorder Passerides) have the largest variation in sperm morphology. Their spermatozoa move by using energy generated in the midpiece, which is formed by multiple mitochondria fusing together during spermatogenesis. However, very little is known regarding the number of mitochondria required to form the songbird midpiece. Based on previous research showing an association of midpiece length and mitochondrial DNA (mtDNA) copy number in the zebra finch Taeniopygia guttata, we hypothesize that songbird species with longer sperm midpieces have more copies of mtDNA. We estimated the sperm mtDNA copy number in 19 species from 10 families within Passerides, covering a broad range of midpiece sizes. Mitochondrial and nuclear DNA abundance were determined using droplet digital PCR (ddPCR) and the ratio between mitochondrial and single-copy nuclear genes was used to estimate mtDNA copy number per spermatozoon. We found that species differ in their average mtDNA copy number, but the variation was small and not significantly related to midpiece length. A possible explanation is that mitochondrial genomes are eliminated in the spermatids during spermatogenesis.

• Damnjanović, Dragomir; Nazarizadeh, Masoud; Wisniewska, Monika M.; Pavel, Václav; Chutný, Bohumír & Johnsen, Arild [Vis alle 8 forfattere av denne artikkelen] (2024). Limited genetic depletion despite extinction risk: genomic diversity of a peripheral population of red-spotted bluethroats in Central Europe. Zoological Journal of the Linnean Society. ISSN 0024-4082. 201(4). doi: 10.1093/zoolinnean/zlae094. Fulltekst i vitenarkiv Vis sammendrag

  Small and isolated populations are at risk of local extinction, either due to the reduction of genetic diversity or due to stochastic events. We assessed genetic diversity in populations of the red-spotted (Luscinia svecica svecica) and white-spotted bluethroat (L. s. cyanecula) subspecies from six European sites, focusing on a peripheral and declining, red-spotted population from Central Europe (Krkonoše Mountains, Czech Republic). Analysis of population structure using mitochondrial sequences (cytochrome b) and ddRAD genomic data revealed that the two subspecies form clearly defined clusters, but traces of possible admixture were found in three populations of the white-spotted bluethroat. Demographic history reconstruction indicates past population range expansion in both subspecies, while the occurrence of short (0.4 Mbp) runs of homozygosity (ROH) segments suggests possible inbreeding 50 to 200 generations ago. Interestingly, although established by a small number of individuals, the Krkonoše population show reduced genetic diversity in only one measure of summary statistics, possibly due to sustained gene flow. Correspondingly, nine highly homozygous genes were recovered within a 2.6-Mbp long ROH region on the Chr 5. Thus, we found only a small reduction of genetic diversity in a population facing extinction, contrary to the expectations for a geographically distant and small population.

• Damnjanović, Dragomir; Nazarizadeh, Masoud; Pavel, Václav; Chutný, Bohumír; Johnsen, Arild & Nováková, Milena [Vis alle 7 forfattere av denne artikkelen] (2024). Expanding the known haemosporidian parasite diversity in Eurasian bluethroat (Luscinia svecica) subspecies through amplicon sequencing. International Journal for Parasitology. ISSN 0020-7519. doi: 10.1016/j.ijpara.2024.11.007. Fulltekst i vitenarkiv
• Grøndahl, Finn Audun & Johnsen, Arild (2024). Combining biometrics and genetics to distinguish two subspecies of the Great Cormorant Phalacrocorax carbo carbo and P. c. sinensis at an inland lake in southeast Norway. Ornis Norvegica. 47, s. 25–40. doi: 10.15845/on.v47.4019. Fulltekst i vitenarkiv Vis sammendrag

  Great Cormorants Phalacrocorax carbo are now regularly seen in inland watercourses in southeast Norway, after the P. c. sinensis subspecies first established breeding colonies in coastal south Norway in 1996. Although both the sinensis and carbo subspecies occur, the ratio between them is unknown. We tested the accuracy of subspecific identification based on biometrics and genetic analyses in 75 Great Cormorants that drowned in fishing nets in a lake in southeast Norway during the period 2009-2020. Primarily based on the gular pouch angle (GPA), we classified 40 individuals to the carbo subspecies and 35 individuals to the sinensis subspecies. Eight of the carbo individuals and 14 of the sinensis individuals were within the overlapping range of GPA and were therefore classified to subspecies by supplementary measurements (bill depth minimum and bill length). Genetic analyses were based on seven polymorphic microsatellite markers. Assuming one panmictic population, we performed Structure analyses to separate the genotypes into two assumed genetic clusters. The two clusters, carbo and sinensis, could only be separated when adding information about morphological subspecies identities for the carbo, sinensis and carbo/sinensis groups. The sinensis and the carbo/sinensis groups belonged almost entirely to one genetic cluster, whereas the carbo group consisted of individuals with varying proportions of mixed ancestry. Furthermore, we found significant genetic differentiation between the carbo and sinensis groups, and between the carbo and the carbo/sinensis groups, but no significant differentiation between the sinensis and the carbo/sinensis groups. Our results suggest that gene flow is more common from sinensis into carbo than vice-versa, and that the use of GPA < 73° has limitations for the identification of Great Cormorant subspecies in areas where both forms occur. We conclude that the numbers of carbo vs. sinensis individuals in our sample were 32 and 43, respectively.

• Bagdonaite, Laima; Leder, Erica Helen; Lifjeld, Jan Terje; Johnsen, Arild & Mauvisseau, Quentin (2024). Assessing reliability and accuracy of qPCR, dPCR and ddPCR for estimating mtDNA copy number in songbird blood and sperm cells. BioRxiv. ISSN 0362-4331. doi: 10.1101/2024.11.08.622696. Fulltekst i vitenarkiv Vis sammendrag

  Mitochondrial DNA copy number varies across species, individuals and cell types. Two avian cell types carrying a relatively low number of mitochondria are the red blood cells and spermatozoa. While previous studies investigating variation of mitochondrial abundance in animal sperm have generally used quantitative PCR (qPCR), this method shows potential limitations when quantifying low abundant targets. To mitigate such issues, we investigated and compared the reliability and accuracy of qPCR, digital PCR (dPCR) and droplet digital PCR (ddPCR) to quantify high and low concentration DNA. Using synthetic DNA, we found that both dPCR and ddPCR displayed lower Limit of Detection and Limit of Quantification than qPCR. Using DNA extracted from blood and sperm cells of Eurasian Siskin, we found that qPCR, dPCR and ddPCR reliably quantified mitochondrial DNA in sperm samples, but showed significant differences when analyzing typically lower levels of mtDNA in blood. We found that ddPCR consistently showed lower variation among replicates. These analyses provide critical insights and recommendations for future studies aiming to quantify target mtDNA. Our study indicates that dPCR and ddPCR are the preferred methods when working with samples with low abundance of mtDNA.

• Benjaminsen, Stine Charlotte; Dehnhard, Nina; Herzke, Dorte; Johnsen, Arild; Anker-Nilssen, Tycho & Bourgeon, Sophie [Vis alle 10 forfattere av denne artikkelen] (2024). The challenges of opportunistic sampling when comparing prevalence of plastics in diving seabirds: A multi-species example from Norway. Marine Pollution Bulletin. ISSN 0025-326X. 199. doi: 10.1016/j.marpolbul.2024.116037. Fulltekst i vitenarkiv Vis sammendrag

  There is a need for baseline information about how much plastics are ingested by wildlife and potential negative consequences thereof. We analysed the frequency of occurrence (FO) of plastics >1 mm in the stomachs of five pursuit-diving seabird species collected opportunistically. Atlantic puffins (Fratercula arctica) found emaciated on beaches in SW Norway had the highest FO of plastics (58.8 %), followed by emaciated common guillemots (Uria aalge; 9.1 %) also found beached in either SW or SE Norway. No plastics were detected in razorbills (Alca torda), great cormorants (Phalacrocorax carbo), and European shags (Gulosus aristotelis) taken as bycatch in northern Norway. This is the first study to report on plastic ingestion of these five species in northern Europe, and it highlights both the usefulness and limitations of opportunistic sampling. Small sample sizes, as well as an unbalanced sample design, complicated the interpretation of the results.

• Johannessen, Lars Erik; Johnsen, Arild; Koppetsch, Thore; Lifjeld, Jan Terje; Matschiner, Michael & Søli, Geir Einar Ellefsen [Vis alle 7 forfattere av denne artikkelen] (2023). Arctic Specimens in the Zoological Collections at the Natural History Museum, University of Oslo, Norway (NHMO). Collections: A Journal for Museum and Archives Professionals. ISSN 1550-1906. doi: 10.1177/15501906231167574. Fulltekst i vitenarkiv Vis sammendrag

  In the NHMO zoological collections, specimens from the Arctic include about 9,000 mammals and 7,100 birds, whereas the Insect Collection holds about 105,000 specimens plus more than hundred jars with unsorted material. The Fish Collection contains approximately 1,400 specimens, while the Herptile Collection (amphibians & reptiles) holds only thirty-one specimens of three taxa. Many of these specimens originate from expeditions to E Greenland, N Canada, Svalbard, Novaya Zemlya, Finnmark, and NE Siberia in the period 1898 to 1966. Furthermore, the DNA Bank has about 5,600 tissue and extracted DNA samples, mostly sampled from wild animals during the last decades but also from specimens in the voucher collections. Most of the Arctic specimens have been digitized and are available in online data portals like GBIF, except for the Insect Collection, where only the type material and about 30 percent of the total specimens are digitized.

• Johnsen, Arild; Dobbe, Kristine; Sætre, Camilla Lo Cascio; Eybert, Marie-Christine; Marquet, Matthieu & Bonnet, Patrick [Vis alle 7 forfattere av denne artikkelen] (2023). Genetic diversity and sperm characteristics are not associated in two bluethroat (Luscinia svecica) populations. Journal of Avian Biology. ISSN 0908-8857. s. 1–9. doi: 10.1111/jav.03125. Fulltekst i vitenarkiv Vis sammendrag

  Individual heterozygosity may influence the expression of fitness‐related traits, via genome‐wide or local genetic effects. Earlier studies have shown negative relationships between heterozygosity and sperm variation, predominantly in captive, highly inbred populations. Little is known about the possible influence of variation in heterozygosity on sperm traits in wild, outbred populations. We studied two populations of the bluethroat, one from the widely distributed northern subspecies Luscinia. s. svecica and the other from the smaller, more patchily distributed subspecies breeding along the French coast of Brittany L. s. namnetum . The two subspecies differed significantly in body size, plumage colour, sperm traits and the degree of genetic diversity. However, there was no evidence that sperm traits (total length and motility) were influenced by the degree of heterozygosity at the individual level. In contrast, we found that male body size was positively related to heterozygosity across both populations, indicating a possible relationship between overall genetic diversity and general vigour or ability to obtain food. We conclude that sperm traits are unrelated to levels of heterozygosity in the studied outbred and weakly genetically depauperate bluethroat populations.

• Rekdal, Silje Larsen; Anmarkrud, Jarl Andreas; Lifjeld, Jan Terje & Johnsen, Arild (2023). Do female bluethroats without extra-pair offspring have more MHC-compatible social mates? Behavioral Ecology and Sociobiology. ISSN 0340-5443. 77(3). doi: 10.1007/s00265-023-03311-z. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Genes of the major histocompatibility complex (MHC) are crucial for adaptive immunity in jawed vertebrates, and theory predicts that there should be mate choice for optimizing MHC constitution in the offspring. In a previous study, we demonstrated a non-random female choice of extra-pair males in the bluethroat ( Luscinia svecica ), yielding offspring that was closer to an intermediate MHC class II (MHCII) allele count than their within-pair halfsiblings. The present study tests whether social pairs with only within-pair young (WPY) in their brood, in the same study population, had a combined MHC-constitution closer to a presumed intermediate optimum, than social pairs with extra-pair young (EPY), with a corresponding pattern in their offspring. As expected, we found that WPY from pure WPY-broods were more MHC-optimal than WPY from mixed broods, but only in broods of young (second year) males. Correspondingly, there was a tendency for social pairs with only WPY in their brood to be more MHC-compatible than social pairs with EPY in their brood, when the male was young. Older bluethroat males have considerably larger testes than young males, and their higher sperm competitiveness could help them secure paternity in their own brood, also when they are not MHC-compatible. In other words, in the sexual conflict over paternity, females may be more likely to realise their preference for a MHC-compatible mate when paired to a young male. As a possible fitness indicator, immune responsiveness to an injected antigen (PHA) was elevated for offspring closer to “the golden mean” in MHCII allele count. Significance statement This study contributes to our understanding of MHC-based mate choice in extra-pair mating systems, by showing that female bluethroats ( Luscinia svecica ) with an MHCII-compatible social mate tend to have no extra-pair young in their brood, but only when the social male is young. This elucidates a possible sexual conflict, in which older social males are able to override female preferences and prevent other males from gaining paternity in their brood through higher sperm production. Studying systems in which extra-pair paternity occurs offers an insight into the genetic benefits of mate choice, as extra-pair males, in contrast to social males, generally contribute only sperm. Further, the strict and thorough genotyping scheme applied in this study enabled us to demonstrate a preference for “the golden mean” in MHC-diversity in a species with one of the highest MHC class II-diversity known to date.

• Grønstøl, Gaute; Danielsen, Marie; Cramer, Becky; Johannessen, Lars Erik; Johnsen, Arild & Whittington, Emma [Vis alle 7 forfattere av denne artikkelen] (2022). Effects of fixatives and storage duration on avian sperm morphology. Journal of Ornithology. ISSN 2193-7192. 164(1), s. 171–181. doi: 10.1007/s10336-022-02015-x. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Sperm cells are variable both within and among species. To be able to accurately measure sperm cells and understand their function, it is important that sperm cells are preserved in a manner that maintains their structural integrity. Formalin is a widely used fixative and storage medium for sperm cells, but few studies have examined the effect of fixation and long-term storage on their morphological integrity. Ethanol is also a common fixation and storage agent for tissue samples, and here we examine if fixation and storage in formalin or ethanol alters sperm cell size and structural integrity. We found no significant effects of the fixation process on fresh sperm cells fixed in formalin or ethanol. Further, there were no consistent length changes in sperm cells stored in formalin or ethanol over a period of 227 days, or in sperm cells stored in formalin for three years. A comparison across 13–14 years of storage time showed a small but significant reduction in sperm cell length of 0.93%. Furthermore, sperm cells initially fixed in formalin remained quite stable in dry storage on glass slides for a minimum of six months (we found a mean reduction in sperm cell length of 0.18% after 6 months). The proportion of sperm cells with head damage was, however, much higher for samples stored in ethanol than for those stored in formalin. Overall, 70% of sperm cells had acrosome damage in ethanol versus only 3% in formalin. Finding intact sperm cells for measuring length, therefore, required greater effort in ethanol samples than in formalin samples. Our findings indicate that use of sperm cells from long-term storage for the study of sperm morphometrics is justified for either fixative, although formalin clearly preserves the sperm cells better.

• Poignet, Manon; Baránková, Lucie; Reif, Jiri; Stopka, Pavel; Stopková, Romana & Frolikova, Michaela [Vis alle 13 forfattere av denne artikkelen] (2022). Sperm morphology and performance in relation to postmating prezygotic isolation in two recently diverged passerine species. Scientific Reports. 12(1). doi: 10.1038/s41598-022-26101-5. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Divergence in sperm phenotype and female reproductive environment may be a common source of postmating prezygotic (PMPZ) isolation between species. However, compared to other reproductive barriers it has received much less attention. In this study, we examined sperm morphology and velocity in two hybridizing passerine species, the common nightingale ( Luscinia megarhynchos ) and thrush nightingale ( L. luscinia ). In addition, we for the first time characterized a passerine female reproductive tract fluid proteome. We demonstrate that spermatozoa of the common nightingale have significantly longer and wider midpiece (proximal part of the flagellum containing mitochondria) and longer tail compared to spermatozoa of thrush nightingale. On the other hand, they have significantly shorter and narrower acrosome. Importantly, these differences did not have any effect on sperm velocity. Furthermore, the fluid from the reproductive tract of common nightingale females did not differentially affect velocity of conspecific and heterospecific sperm. Our results indicate that the observed changes in the flagellum and acrosome size are unlikely to contribute to PMPZ isolation through differential sperm velocity of conspecific and heterospecific sperm in the female reproductive tract. However, they could affect other postcopulatory processes, which might be involved in PMPZ isolation, such as sperm storage, longevity or sperm-egg interaction.

• Cramer, Emily Rebecca A; Garcia-del-Rey, Eduardo; Johannessen, Lars Erik; Laskemoen, Terje; Marthinsen, Gunnhild & Johnsen, Arild [Vis alle 7 forfattere av denne artikkelen] (2021). Longer Sperm Swim More Slowly in the Canary Islands Chiffchaff. Cells. 10(6). doi: 10.3390/cells10061358. Fulltekst i vitenarkiv Vis sammendrag

  Sperm swimming performance affects male fertilization success, particularly in species with high sperm competition. Understanding how sperm morphology impacts swimming performance is therefore important. Sperm swimming speed is hypothesized to increase with total sperm length, relative flagellum length (with the flagellum generating forward thrust), and relative midpiece length (as the midpiece contains the mitochondria). We tested these hypotheses and tested for divergence in sperm traits in five island populations of Canary Islands chiffchaff (Phylloscopus canariensis). We confirmed incipient mitochondrial DNA differentiation between Gran Canaria and the other islands. Sperm swimming speed correlated negatively with total sperm length, did not correlate with relative flagellum length, and correlated negatively with relative midpiece length (for Gran Canaria only). The proportion of motile cells increased with relative flagellum length on Gran Canaria only. Sperm morphology was similar across islands. We thus add to a growing number of studies on passerine birds that do not support sperm morphology–swimming speed hypotheses. We suggest that the swimming mechanics of passerine sperm are sufficiently different from mammalian sperm that predictions from mammalian hydrodynamic models should no longer be applied for this taxon. While both sperm morphology and sperm swimming speed are likely under selection in passerines, the relationship between them requires further elucidation.

• Rekdal, Silje Larsen; Anmarkrud, Jarl Andreas; Lifjeld, Jan Terje & Johnsen, Arild (2021). Elevated phytohaemagglutinin‐induced skin‐swelling response at an intermediate number of MHC class II alleles in bluethroat nestlings. Journal of Avian Biology. ISSN 0908-8857. doi: 10.1111/jav.02734. Fulltekst i vitenarkiv Vis sammendrag

  Genes of the major histocompatibility complex (MHC) are crucial for adaptive immunity, and theory predicts that the optimal number of alleles is intermediate rather than maximal. Support for such an intermediate optimum in MHC allele count has mainly been demonstrated in studies on parasite load and reproductive traits. In this study we tested if an intermediate number of MHC class II (MHCII) alleles based on positively selected sites was correlated with an increased skin-swelling response to two consecutive injections of phytohaemagglutinin (PHA) in bluethroat Luscinia svecica nestlings. We found that nestlings that were closer to the population mean in their number of alleles had a higher response to the first injection, supporting an intermediate, optimal number of alleles. After the second PHA injection, we found that the skin swelling was associated with MHCII allele count only at the among-brood level, and with paternity (extra-pair offspring had a larger swelling than within-pair offspring). We therefore conclude that the PHA response is partly correlated with MHCII allele count, but that additional factors must be involved in both the PHA response and in female extra-pair mate choice in this species.

• Magnussen, Trude; Johnsen, Arild; Kjærandsen, Jostein; Struck, Torsten H & Søli, Geir Einar Ellefsen (2021). Molecular phylogeny of Allodia (Diptera: Mycetophilidae) constructed using genome skimming. Systematic Entomology. ISSN 0307-6970. s. 1–15. doi: 10.1111/syen.12529. Fulltekst i vitenarkiv Vis sammendrag

  In this study, we use low-coverage shotgun sequencing of genomic DNA, commonly referred to as genome skimming, to investigate the phylogenetic relationships of the fungus gnat genus Allodia Winnertz (Mycetophilidae, Mycetophilinae, Exechiini). Nineteen specimens, representing 16 in-group and three outgroup taxa, were successfully sequenced and molecular markers of both mitochondrial and nuclear origin were retrieved. The phylogenetic analyses of 13 protein-coding mitochondrial genes, two ribosomal mitochondrial genes and the nuclear ribosomal 18S and 28S strongly support the monophyly of its two subgenera Allodia s.s. and Brachycampta. Complete mitochondrial genomes of 15 species were assembled, which enables further comparisons with the mitochondrial genomes of other Diptera. Overall, the methodology used in this study proved successful and promising for other dipteran groups. In addition to the phylogenetic reconstruction, the morphological characters previously used to separate the two subgenera were evaluated and re-examined. Together with the composite structure of the male genitalia, we consider details of the scutal bristles appropriate for separating the two groups. Based on the achieved results, we reinstate Brachycampta stat. rev. as a separate genus.

• Omotoriogun, Taiwo Crossby; Albrecht, Tomas; Gohli, Jostein; Horák, David; Johannessen, Lars Erik & Johnsen, Arild [Vis alle 12 forfattere av denne artikkelen] (2020). Sperm length variation among Afrotropical songbirds reflects phylogeny rather than adaptations to the tropical environment. Zoology. ISSN 0944-2006. 140. doi: 10.1016/j.zool.2020.125770. Fulltekst i vitenarkiv Vis sammendrag

  Sperm cells vary tremendously in size and shape across the animal kingdom. In songbirds (Aves: Passeri), sperm have a characteristic helical form but vary considerably in size. Most of our knowledge about sperm morphology in this group stems from studies of species in the Northern temperate zone, while little is known about the numerous species in the tropics. Here we examined sperm size in 125 Afrotropical songbird species with emphasis on the length of the major structural components (head, midpiece, flagellum), and total sperm length measured using light microscopy. Mean total sperm length varied from 51 μm to 212 μm across species. Those belonging to the Corvoidea superfamily had relatively short sperm with a small midpiece, while those of the three major Passeridan superfamilies Passeroidea, Muscicapoidea and Sylvioidea showed large interspecific variation in total sperm length and associated variation in midpiece length. These patterns are consistent with previous findings for temperate species in the same major clades. A comparative analysis with songbird species from the Northern temperate zone (N = 139) showed large overlap in sperm length ranges although certain temperate families (e.g. Parulidae, Emberizidae) typically have long sperm and certain Afrotropical families (e.g. Cisticolidae, Estrildidae) have relatively short sperm. Afrotropical and temperate species belonging to the same families showed no consistent contrasts in sperm length. Sperm length variation among Afrotropical and Northern temperate songbirds exhibits a strong phylogenetic signal with little or no evidence for any directional latitudinal effect among closely related taxa.

• Cramer, Emily Rebecca A; Rowe, Melissah; Eroukhmanoff, Fabrice; Lifjeld, Jan Terje; Sætre, Glenn-Peter & Johnsen, Arild (2019). Measuring sperm swimming performance in birds: effects of dilution, suspension medium, mechanical agitation, and sperm number. Journal of Ornithology = Journal fur Ornithologie. ISSN 0021-8375. s. 1–11. doi: 10.1007/s10336-019-01672-9. Fulltekst i vitenarkiv Vis sammendrag

  Sperm swimming performance, including swimming speed and the proportion of motile cells, may strongly affect fertilization success. However, little is known about how methodological factors affect in vitro measurement of these parameters. We compare the swimming performance of sperm from House Sparrows (Passer domesticus) and Spanish Sparrows (Passer hispaniolensis) in two standard suspension media, at two different dilutions, and with different degrees of cell agitation. Further, we conduct a resampling analysis to investigate sample size effects. Sperm performance was generally reduced when sperm were diluted, or when suspended in phosphate-buffered saline (PBS) rather than a medium containing additional nutrients. Sperm performance was particularly low when they were diluted more and suspended in PBS, suggesting that seminal fluid may provide compounds that enhance performance but that these are less available following dilution. Mechanical agitation of the cells by vigorous pipetting increased the proportion of motile cells. Between-male repeatability, assessed on a single sample measured in multiple conditions, was moderate and significant, suggesting that similar results may be obtained regardless of the methodology used to assess sperm motion. We found no evidence of biased results when low numbers of cells per male were used in analysis, though precision increased substantially as sample size increased from five to 20 or more cells per male. We recommend using the same suspension media and similar sperm concentrations and levels of agitation, to the greatest degree possible, and including as many individuals as possible in analyses, even when some individuals are represented by few sperm cells.

• Støstad, Hanna Nyborg; Rowe, Melissah; Johnsen, Arild; Tomasek, Oldrich; Albrecht, Tomas & Lifjeld, Jan Terje (2019). Sperm head abnormalities are associated with excessive omega-6 fatty acids in two finch species feeding on sunflower seeds. Journal of Avian Biology. ISSN 0908-8857. 50(3), s. 1–12. doi: 10.1111/jav.02056. Fulltekst i vitenarkiv Vis sammendrag

  In a rapidly changing world, it is important to understand how urban environments impact wildlife. For example, supplementary feeding of birds, though well‐intended, might have unexpected negative effects on the health of individual animals. Sunflower seeds are commonly provided in garden bird feeders, but they contain high levels of linoleic acid (LA), an omega‐6 polyunsaturated fatty acid (PUFA). Omega‐6 PUFAs are associated with increased oxidative stress, which can damage cell membranes, and in particular sperm cells. We assessed the level of LA in the blood of two seed‐eating finch species, greenfinches Chloris chloris and hawfinches Coccothraustes coccothraustes , caught in and in environments with direct access to sunflower seed feeders (Norway), and compared these with the level of LA in a smaller number of individuals sampled in in a rural area with low incidence of sunflower seed feeders (Czech Republic). Furthermore, we investigated the relationship between the proportion of LA in the blood (as well as the proportion of 10 other fatty acids) and sperm quality (the frequency of sperm head abnormalities and sperm swimming speed). We found that both finch species, but particularly greenfinches caught near feeders, exhibited levels of LA that were considerably higher than those previously reported for other wild birds. We also found that the proportion of LA was positively correlated with the frequency of abnormal sperm heads (sperm missing the acrosome), while there was no significant effect of fatty acid composition on sperm swimming speed. Our results indicate that the sperm quality of finches may be negatively affected by a high intake of sunflower seeds, adding to a growing body of research showing that supplementary feeding may have detrimental side effects for urban animals. This is particularly relevant for the greenfinch, which is currently affected by disease and population declines.

• Støstad, Hanna Nyborg; Rowe, Melissah; Johnsen, Arild & Lifjeld, Jan Terje (2019). Sperm head abnormalities are more frequent in songbirds with more helical sperm: A possible trade-off in sperm evolution. Journal of Evolutionary Biology. ISSN 1010-061X. s. 1–9. doi: 10.1111/jeb.13446. Fulltekst i vitenarkiv Vis sammendrag

  Sperm morphology varies enormously across the animal kingdom. Whilst knowledge of the factors that drive the evolution of interspecific variation in sperm morphology is accumulating, we currently have little understanding of factors that may constrain evolutionary change in sperm traits. We investigated whether susceptibility to sperm abnormalities could represent such a constraint in songbirds, a group characterized by a distinctive helical sperm head shape. Specifically, using 36 songbird species and data from light and scanning electron microscopy, we examined among‐species correlations between the occurrence of sperm head abnormalities and sperm morphology, as well as the correlation between sperm head abnormalities and two indicators of sperm competition. We found that species with more helically shaped sperm heads (i.e., a wider helical membrane and more pronounced cell waveform) had a higher percentage of abnormal sperm heads than species with less helical sperm (i.e., relatively straight sperm) and that sperm head traits were better predictors of head abnormalities than total sperm length. In contrast, there was no correlation between sperm abnormalities and the level of sperm competition. Given that songbird species with more pronounced helical sperm have higher average sperm swimming speed, our results suggest an evolutionary trade‐off between sperm performance and the structural integrity of the sperm head. As such, susceptibility to morphological abnormalities may constrain the evolution of helical sperm morphology in songbirds.

• Lindsay, Willow R.; Andersson, Staffan; Bererhi, Badreddine; Höglund, Jacob; Johnsen, Arild & Kvarnemo, Charlotta [Vis alle 16 forfattere av denne artikkelen] (2019). Endless forms of sexual selection. PeerJ. doi: 10.7717/peerj.7988. Fulltekst i vitenarkiv Vis sammendrag

  In recent years, the field of sexual selection has exploded, with advances in theoretical and empirical research complementing each other in exciting ways. This perspective piece is the product of a ``stock-taking'' workshop on sexual selection and sexual conflict. Our aim is to identify and deliberate on outstanding questions and to stimulate discussion rather than provide a comprehensive overview of the entire field. These questions are organized into four thematic sections we deem essential to the field. First we focus on the evolution of mate choice and mating systems. Variation in mate quality can generate both competition and choice in the opposite sex, with implications for the evolution of mating systems. Limitations on mate choice may dictate the importance of direct vs. indirect benefits in mating decisions and consequently, mating systems, especially with regard to polyandry. Second, we focus on how sender and receiver mechanisms shape signal design. Mediation of honest signal content likely Depends on integration of temporally variable social and physiological costs that are o measure. We view the neuroethology of sensory and cognitive receiver biases as the main key to signal form and the `aesthetic sense' proposed by Darwin. Since a receiver bias is sufficient to both initiate and drive ornament or armament exaggeration, without a genetically correlated or even coevolving receiver, this may be the appropriate `null model' of sexual selection. Thirdly, we focus on the genetic architecture of sexually selected traits. Despite advances in modern molecular techniques, the number and identity of genes underlying performance, display and secondary sexual traits remains largely unknown. In-depth investigations into the genetic basis of sexual dimorphism in the context of long-term field studies will reveal constraints and trajectories of sexually selected trait evolution. Finally, we focus on sexual selection and conflict as drivers of speciation. Population divergence and speciation are often influenced by an interplay between sexual and natural selection. The extent to which sexual selection promotes or counteracts population divergence may vary depending on the genetic architecture of traits as well as the covariance between mating competition and local adaptation. Additionally, post-copulatory processes, such as selection against heterospecific sperm, may influence the importance of sexual selection in speciation. We propose that efforts to resolve these four themes can catalyze conceptual progress in the field of sexual selection, and we offer potential avenues of research to advance this progress.

• Rekdal, Silje Larsen; Anmarkrud, Jarl Andreas; Lifjeld, Jan Terje & Johnsen, Arild (2019). Extra‐pair mating in a passerine bird with highly duplicated major histocompatibility complex class II: Preference for the golden mean. Molecular Ecology. ISSN 0962-1083. doi: 10.1111/mec.15273. Fulltekst i vitenarkiv Vis sammendrag

  Genes of the major histocompatibility complex (MHC) are essential in vertebrate adaptive immunity, and they are highly diverse and duplicated in many lineages. While it is widely established that pathogen‐mediated selection maintains MHC diversity through balancing selection, the role of mate choice in shaping MHC diversity is debated. Here, we investigate female mating preferences for MHC class II (MHCII) in the bluethroat (Luscinia svecica), a passerine bird with high levels of extra‐pair paternity and extremely duplicated MHCII. We genotyped family samples with mixed brood paternity and categorized their MHCII alleles according to their functional properties in peptide binding. Our results strongly indicate that females select extra‐pair males in a nonrandom, self‐matching manner that provides offspring with an allelic repertoire size closer to the population mean, as compared to offspring sired by the social male. This is consistent with a compatible genes model for extra‐pair mate choice where the optimal allelic diversity is intermediate, not maximal. This golden mean presumably reflects a trade‐off between maximizing pathogen recognition benefits and minimizing autoimmunity costs. Our study exemplifies how mate choice can reduce the population variance in individual MHC diversity and exert strong stabilizing selection on the trait. It also supports the hypothesis that extra‐pair mating is adaptive through altered genetic constitution in offspring.

• Albrecht, Tomas; Opletalová, Kamila; Reif, Jiri; Janousek, Vaclav; Pialek, Lubomir & Cramer, Emily Rebecca A [Vis alle 8 forfattere av denne artikkelen] (2019). Sperm divergence in a passerine contact zone: Indication of reinforcement at the gametic level. Evolution. ISSN 0014-3820. 73(2), s. 202–213. doi: 10.1111/evo.13677. Fulltekst i vitenarkiv Vis sammendrag

  Postcopulatory sexual selection may promote evolutionary diversification in sperm form, but the contribution of between‐species divergence in sperm morphology to the origin of reproductive isolation and speciation remains little understood. To assess the possible role of sperm diversification in reproductive isolation, we studied sperm morphology in two closely related bird species, the common nightingale (Luscinia megarhynchos ) and the thrush nightingale (Luscinia luscinia ), that hybridize in a secondary contact zone spanning Central and Eastern Europe. We found: (1) striking divergence between the species in total sperm length, accompanied by a difference in the length of the mitochondrial sperm component; (2) greater divergence between species in sperm morphology in sympatry than in allopatry, with evidence for character displacement in sperm head length detected in L. megarhynchos ; (3) interspecific hybrids showing sperm with a length intermediate between the parental species, but no evidence for decreased sperm quality (the proportion of abnormal spermatozoa in ejaculates). Our results demonstrate that divergence in sperm morphology between the two nightingale species does not result in intrinsic postzygotic isolation, but may contribute to postcopulatory prezygotic isolation. This isolation could be strengthened in sympatry by reinforcement.

• Lifjeld, Jan Terje; Gohli, Jostein; Albrecht, Tomas; Garcia-del-Rey, Eduardo; Johannessen, Lars Erik & Kleven, Oddmund [Vis alle 10 forfattere av denne artikkelen] (2019). Evolution of female promiscuity in Passerides songbirds. BMC Evolutionary Biology. 19(1). doi: 10.1186/s12862-019-1493-1. Fulltekst i vitenarkiv Vis sammendrag

  Background: Female promiscuity is highly variable among birds, and particularly among songbirds. Comparative work has identified several patterns of covariation with social, sexual, ecological and life history traits. However, it is unclear whether these patterns reflect causes or consequences of female promiscuity, or if they are byproducts of some unknown evolutionary drivers. Moreover, factors that explain promiscuity at the deep nodes in the phylogenetic tree may be different from those important at the tips, i.e. among closely related species. Here we examine the relationships between female promiscuity and a broad set of predictor variables in a comprehensive data set (N = 202 species) of Passerides songbirds, which is a highly diversified infraorder of the Passeriformes exhibiting significant variation in female promiscuity. Results: Female promiscuity was highly variable in all major clades of the Passerides phylogeny and also among closely related species. We found several significant associations with female promiscuity, albeit with fairly small effect sizes (all R2 ≤ 0.08). More promiscuous species had: 1) less male parental care, particularly during the early stages of the nesting cycle (nest building and incubation), 2) more short-term pair bonds, 3) greater degree of sexual dichromatism, primarily because females were drabber, 4) more migratory behaviour, and 5) stronger premating sexual selection. In a multivariate model, however, the effect of sexual selection disappeared, while the other four variables showed additive effects and together explained about 16% of the total variance in female promiscuity. Female promiscuity showed no relationship with body size, life history variation, latitude or cooperative breeding. Conclusions: We found that multiple traits were associated with female promiscuity, but these associations were generally weak. Some traits, such as reduced parental care in males and more cryptic plumage in females, might even be responses to, rather than causes of, variation in female promiscuity. Hence, the high variation in female promiscuity among Passerides species remains enigmatic. Female promiscuity seems to be a rapidly evolving trait that often diverges between species with similar ecologies and breeding systems. A future challenge is therefore to understand what drives within-lineage variation in female promiscuity over microevolutionary time scales. Keywords: Extrapair paternity, Life history, Mating system, Pair bond, Parental care, Sexual selection

• Sætre, Camilla Lo Cascio; Johnsen, Arild; Stensrud, Even & Cramer, Emily Rebecca A (2018). Sperm morphology, sperm motility and paternity success in the bluethroat (Luscinia svecica). PLOS ONE. 13(3). doi: 10.1371/journal.pone.0192644. Fulltekst i vitenarkiv Vis sammendrag

  Postcopulatory sexual selection may select for male primary sexual characteristics like sperm morphology and sperm motility, through sperm competition or cryptic female choice. However, how such characteristics influence male fertilization success remains poorly understood. In this study, we investigate possible correlations between sperm characteristics and paternity success in the socially monogamous bluethroat (Luscinia svecica svecica), predicting that sperm length and sperm swimming speed is positively correlated with paternity success. In total, 25% (15/61) of broods contained extra-pair offspring and 10% (33/315) of the offspring were sired by extra-pair males. Paternity success did not correlate significantly with sperm morphology or any aspects of sperm motility. Furthermore, sperm morphology and sperm motility did not correlate significantly with male morphological characters that previously have been shown to be associated with paternity success. Thus, the sperm characteristics investigated here do not appear to be strong predictors of paternity success in bluethroats.

• Magnussen, Trude; Kjærandsen, Jostein; Johnsen, Arild & Søli, Geir Einar Ellefsen (2018). Six new species of Afrotropical Allodia (Diptera: Mycetophilidae): DNA barcodes indicate recent diversification with a single origin. Zootaxa. ISSN 1175-5326. 4407(3), s. 301–320. doi: 10.11646/zootaxa.4407.3.1. Fulltekst i vitenarkiv Vis sammendrag

  Only one species of the genus Allodia has been previously recorded from the Afrotropical region, Allodia (Brachycampta) flavorufa Matile, 1978. Six new species are described here, all representing the nominotypical subgenus, Allodia s.s. The new species are described from material collected in different mountainous areas in south and east Africa; A. jaschhofi sp. nov., A. karkloofensis sp. nov., A. drakensbergensis sp. nov., A. nyeriensis sp. nov., A. mazumbaiensis sp. nov. and A. keurbosensis sp. nov. The species are morphologically very similar, and can only be separated based on minor differences in wing venation and characters of the male terminalia. The genetic differences between the species in the DNA barcode region (CO1), however, support delimitation. The origin and distribution of these Afrotropical taxa, in relation to each other and to their Holarctic relatives, is discussed.

• Støstad, Hanna Nyborg; Johnsen, Arild; Lifjeld, Jan Terje & Rowe, Melissah (2018). Sperm head morphology is associated with sperm swimming speed: a comparative study of songbirds using electron microscopy. Evolution. ISSN 0014-3820. 72(9), s. 1918–1932. doi: 10.1111/evo.13555. Fulltekst i vitenarkiv Vis sammendrag

  Sperm exhibit extraordinary levels of morphological diversification across the animal kingdom. In songbirds, sperm have a helically shaped head incorporating a distinct acrosomal membrane or “helical keel,” the form and extent of which varies across species. The functional significance of this helical shape, however, remains unknown. Using scanning electron microscopy, we quantified inter‐ and intraspecific variation in sperm head morphology across 36 songbird species (Passeriformes: Passerida). Using phylogenetic comparative methods, we investigated the relationship between sperm head morphology and both sperm swimming speed and the frequency of extra‐pair young (EPY). We found that species whose sperm had a relatively more pronounced helical form (i.e., long acrosome, short nucleus, wide helical membrane, and a more pronounced waveform along the sperm head “core”) had faster‐swimming sperm. We found no evidence of a relationship between interspecific variation in sperm head morphology and EPY, although we did find that among‐ and within‐male variation in sperm head traits were negatively correlated with EPY. Applying principles of fluid mechanics, we discuss how the helical form of the sperm head may influence swimming speed, and suggest that further studies considering aspects of sperm morphology beyond sperm length are needed to improve our understanding of sperm structure‐function relationships.

• Kearns, Anna Marika; Restani, Marco; Szabo, Ildiko; Schrøder-Nielsen, Audun; Kim, Jin Ah & Richardson, Hayley M. [Vis alle 10 forfattere av denne artikkelen] (2018). Genomic evidence of speciation reversal in ravens. Nature Communications. 9(1). doi: 10.1038/s41467-018-03294-w. Fulltekst i vitenarkiv Vis sammendrag

  Many species, including humans, have emerged via complex reticulate processes involving hybridisation. Under certain circumstances, hybridisation can cause distinct lineages to collapse into a single lineage with an admixed mosaic genome. Most known cases of such ‘speciation reversal’ or ‘lineage fusion’ involve recently diverged lineages and anthropogenic perturbation. Here, we show that in western North America, Common Ravens (Corvus corax) have admixed mosaic genomes formed by the fusion of non-sister lineages (‘California’ and ‘Holarctic’) that diverged ~1.5 million years ago. Phylogenomic analyses and concordant patterns of geographic structuring in mtDNA, genome-wide SNPs and nuclear introns demonstrate long-term admixture and random interbreeding between the non-sister lineages. In contrast, our genomic data support reproductive isolation between Common Ravens and Chihuahuan Ravens (C. cryptoleucus) despite extensive geographic overlap and a sister relationship between Chihuahuan Ravens and the California lineage. These data suggest that the Common Raven genome was formed by secondary lineage fusion and most likely represents a case of ancient speciation reversal that occurred without anthropogenic causes.

• Králová, Tereza; Albrecht, Tomas; Bryja, Josef; Horák, David; Johnsen, Arild & Lifjeld, Jan Terje [Vis alle 10 forfattere av denne artikkelen] (2018). Signatures of diversifying selection and convergence acting on passerine Toll-like receptor 4 in an evolutionary context. Molecular Ecology. ISSN 0962-1083. 27(13), s. 2871–2883. doi: 10.1111/mec.14724. Fulltekst i vitenarkiv Vis sammendrag

  Positive selection acting on Toll‐like receptors (TLRs) has been recently investigated to reveal evolutionary mechanisms of host–pathogen molecular co‐adaptation. Much of this research, however, has focused mainly on the identification of sites predicted to be under positive selection, bringing little insight into the functional differences and similarities among species and a limited understanding of convergent evolution in the innate immune molecules. In this study, we provide evidence of phenotypic variability in the avian TLR4 ligand‐binding region (LBR), the direct interface between host and pathogen molecular structures. We show that 55 passerine species vary substantially in the distribution of electrostatic potential on the surface of the receptor, and based on these distinct patterns, we identified four species clusters. Seven of the 34 evolutionarily nonconservative and positively selected residues correspond topologically to sites previously identified as being important for lipopolysaccharide, lipid IVa or MD‐2 binding. Five of these positions codetermine the identity of the charge clusters. Groups of species that host‐related communities of pathogens were predicted to cluster based on their TLR4 LBR charge. Despite some evidence for convergence among taxa, there were no clear associations between the TLR4 LBR charge distribution and any of the general ecological characteristics compared (migration, latitudinal distribution and diet). Closely related species, however, mostly belonged to the same surface charge cluster indicating that phylogenetic constraints are key determinants shaping TLR4 adaptive evolution. Our results suggest that host innate immune evolution is consistent with Fahrenholz's rule on the cospeciation of hosts and their parasites.

• Rekdal, Silje Larsen; Anmarkrud, Jarl Andreas; Johnsen, Arild & Lifjeld, Jan Terje (2018). Genotyping strategy matters when analyzing hypervariable major histocompatibility complex-Experience from a passerine bird. Ecology and Evolution. 8(3), s. 1680–1692. doi: 10.1002/ece3.3757. Fulltekst i vitenarkiv
• Johnsen, Arild; Kearns, Anna Marika; Omland, Kevin E. & Anmarkrud, Jarl Andreas (2017). Sequencing of the complete mitochondrial genome of the common raven Corvus corax (Aves: Corvidae) confirms mitogenome-wide deep lineages and a paraphyletic relationship with the Chihuahuan raven C. cryptoleucus. PLOS ONE. 12(10). doi: 10.1371/journal.pone.0187316. Fulltekst i vitenarkiv Vis sammendrag

  Previous studies based on single mitochondrial markers have shown that the common raven (Corvus corax) consists of two highly diverged lineages that are hypothesised to have undergone speciation reversal upon secondary contact. Furthermore, common ravens are paraphyletic with respect to the Chihuahuan raven (C. cryptoleucus) based on mitochondrial DNA (mtDNA). Here we explore the causes of mtDNA paraphyly by sequencing whole mitochondrial genomes of 12 common ravens from across the Northern Hemisphere, in addition to three Chihuahuan ravens and one closely related brown-necked raven (C. ruficollis) using a long-range PCR protocol. Our raven mitogenomes ranged between 16925–16928 bp in length. GC content varied from 43.3% to 43.8% and the 13 protein coding genes, two rRNAs and 22 tRNAs followed a standard avian mitochondrial arrangement. The overall divergence between the two common raven clades was 3% (range 0.3–5.8% in 16 regions including the protein coding genes, rRNAs and the control region). Phylogenies constructed from whole mitogenomes recovered the previously found mitochondrial sister relationship between the common raven California clade and the Chihuahuan raven (overall divergence 1.1%), which strengthens the hypothesis that mtDNA paraphyly in the common raven results from speciation reversal of previously distinct Holarctic and California lineages.

• Johnsen, Arild; Pauliny, Angela; Lifjeld, Jan Terje & Blomqvist, Donald (2017). Is telomere length associated with mate choice in a songbird with a high rate of extrapair paternity? PLOS ONE. 12(8). doi: 10.1371/journal.pone.0182446. Fulltekst i vitenarkiv Vis sammendrag

  Telomere length is related to aging in many eukaryotes and the rate of telomere attrition has been suggested to reflect individual genetic quality. Telomere length could thus have implications for mate choice. We investigated telomere length variation in bluethroat Luscinia svecica families with mixed paternity, including social parents, extra-pair fathers and nestlings, testing whether telomere length is associated with social and/or extra-pair mate choice through assortative mating or selection of mates with relatively long telomeres. In adults, relative telomere length (rTL) did not differ between the sexes, nor between two age categories. In chicks, however, rTL decreased with body mass at sampling (an index of nestling age). We found a positive correlation between the rTL of social mates, suggesting assortative mating with respect to telomere length or a correlative thereof. However, extra-pair males did not differ from social mates in rTL, and accordingly there was also no difference between within- and extra-pair young (i.e. half-siblings) when controlling for the effect of mass. We found no relationships between telomere length, age and fitness-related traits in adults, but an intriguing year-difference in telomere length in both sexes. In conclusion, we found no support for the idea that females choose extra-pair males based on their telomere length, but social mate choice seems to be influenced by rTL, possibly through its co-variation with aspects reflecting individual quality, like early arrival at the breeding grounds.

• Garcia, Javier; Johnsen, Arild; Fuertes, Benito & Suarez-Seoane, Susana (2017). Evolutionary divergences in Luscinia svecica subspecies complex - New evidence supporting the uniqueness of the Iberian bluethroat breeding populations. Ornis Fennica. ISSN 0030-5685. 94(3), s. 141–149. Fulltekst i vitenarkiv Vis sammendrag

  The assessment of evolutionary divergences within subspecies complexes provide an effective short-cut for estimating intraspecific genetic diversity, which is relevant for conservation actions. We explore new evidence supplementing the existing knowledge about the singularity of Iberian bluethroats within the Luscinia svecica subspecies mosaic. We compared biometric traits of Iberian males (L. s. azuricollis) to the closest subspecies (L. s. cyanecula, L. s. namnetum and L. s. magna) using general linear models and analysed the correlations between biometric and genetic differentiation (based on nuclear microsatellites) among the target subspecies with a Mantel test. Biometric differences were calculated using 63 museum skins and 63 live specimens. Genetic distances were estimated in a sample of 136 individuals. An additional characterisation of the plumage of Iberian males was shaped from 22 live specimens. We highlight the distinctiveness of Iberian birds within the subspecies mosaic since L. s. azuricollis had longer wings than L. s. cyanecula and L. s. namnetum, but shorter wings than L. s. magna.Indeed, L. s. azuricollis had longer tarsus and bill than L. s. namnetum, but shorter bill than L. s. magna.Biometric divergence was not significantly associated with genetic distance. Iberian males showed an all-blue plastron in 77% of specimens, a mostly non-marked black band and no white band, which distinguished them from males of L. s. cyanecula and L. s. namnetum. We conclude the importance of considering phenotypic and genotypic differences at subspecies level, which is essential for designing realistic conservation strategies addressed to preserve species genetic diversity patterns. This article was originally published in Ornis Fennica. © 2017 Finnish Ornithological Society

• Boumans, Louis; Hogner, Silje; Brittain, John Edward & Johnsen, Arild (2017). Ecological speciation by temporal isolation in a population of the stonefly Leuctra hippopus (Plecoptera, Leuctridae). Ecology and Evolution. 7(5), s. 1635–1649. doi: 10.1002/ece3.2638. Fulltekst i vitenarkiv Vis sammendrag

  Stream dwelling invertebrates are ideal candidates for the study of ecological speciation as they are often adapted to particular environmental conditions within a stream and inhabit only certain reaches of a drainage basin, separated by unsuitable habitat. We studied an atypical population of the stonefly Leuctra hippopus at a site in central Norway, the Isterfoss rapids, in relation to three nearby and two remote conspecific populations. Adults of this population emerge about a month earlier than those of nearby populations, live on large boulders emerging from the rapids, and are short-lived. This population also has distinct morphological features and was studied earlier during the period 1975–1990. We reassessed morphological distinctness with new measurements and added several analyses of genetic distinctness based on mitochondrial and nuclear sequence markers, as well as AFLP fingerprinting and SNPs mined from RAD sequences. The Isterfoss population is shown to be most closely related to its geographical neighbors, yet clearly morphologically and genetically distinct and homogeneous. We conclude that this population is in the process of sympatric speciation, with temporal isolation being the most important direct barrier to gene flow. The shift in reproductive season results from the particular temperature and water level regime in the Isterfoss rapids. The distinct adult body shape and loss of flight are hypothesized to be an adaptation to the unusual habitat. Ecological diversification on small spatial and temporal scales is one of the likely causes of the high diversity of aquatic insects.

• Cramer, Emily Rebecca A; Stensrud, Even; Marthinsen, Gunnhild; Hogner, Silje; Johannessen, Lars Erik & Laskemoen, Terje [Vis alle 10 forfattere av denne artikkelen] (2016). Sperm performance in conspecific and heterospecific female fluid. Ecology and Evolution. doi: 10.1002/ece3.1977. Fulltekst i vitenarkiv Vis sammendrag

  Divergent sexual selection within allopatric populations may result in divergent sexual phenotypes, which can act as reproductive barriers between populations upon secondary contact. This hypothesis has been most tested on traits involved in precopulatory sexual selection, with less work focusing on traits that act after copulation and before fertilization (i.e., postcopulatory prezygotic traits), particularly in internally fertilizing vertebrates. However, postcopulatory sexual selection within species can also drive trait divergence, resulting in reduced performance of heterospecific sperm within the female reproductive tract. Such incompatibilities, arising as a by-product of divergent postcopulatory sexual selection in allopatry, can represent reproductive barriers, analogous to species-assortative mating preferences. Here, we tested for postcopulatory prezygotic reproductive barriers between three pairs of taxa with diverged sperm phenotypes and moderate-to-high opportunity for postcopulatory sexual selection (barn swallows Hirundo rustica versus sand martins Riparia riparia, two subspecies of bluethroats, Luscinia svecica svecica versus L. s. namnetum, and great tits Parus major versus blue tits Cyanistes caeruleus). We tested sperm swimming performance in fluid from the outer reproductive tract of females, because the greatest reduction in sperm number in birds occurs as sperm swim across the vagina. Contrary to our expectations, sperm swam equally well in fluid from conspecific and heterospecific females, suggesting that postcopulatory prezygotic barriers do not act between these taxon pairs, at this stage between copulation and fertilization. We therefore suggest that divergence in sperm phenotypes in allopatry is insufficient to cause widespread postcopulatory prezygotic barriers in the form of impaired sperm swimming performance in passerine birds.

• Eroukhmanoff, Fabrice; Rowe, Melissah; Cramer, Emily Rebecca A; Haas, Fredrik; Hermansen, Jo Skeie & Runemark, Anna [Vis alle 8 forfattere av denne artikkelen] (2016). Experimental evidence for ovarian hypofunction in sparrow hybrids. Avian Research. 7. doi: 10.1186/s40657-016-0038-1. Fulltekst i vitenarkiv Vis sammendrag

  Background Postzygotic isolation in the form of reduced viability and/or fertility of hybrids may help maintain species boundaries in the face of interspecific gene flow. Past hybridization events between house sparrows (Passer domesticus) and Spanish sparrows (P. hispaniolensis) have given rise to a homoploid hybrid species, the Italian sparrow (P. italiae). Although genetic incompatibilities are known to isolate these three species, the biological consequences of these incompatibilities are still unknown in early generation hybrids. Methods We investigated whether F1 hybrids between house and Spanish sparrows experience reduced viability or fertility. More specifically, we generated hybrids through controlled crosses in aviaries, and compared ovaries of female hybrids with female of pure-species sparrows. Results We found that overall, hybrid ovaries were underdeveloped and that half of all female hybrids exhibited symptoms of ovarian hypofunction (ovarian atrophy and complete absence of developed follicles). Conclusions Fertility in hybrids is a common consequence or post-zygotic barriers between species. We discuss these results in light of previous findings on genetic incompatibilities between the parent species and the potential role of incompatibilities in hybrid speciation, a rare evolutionary process in birds.

• Mutanen, Marko; Kivelä, Sami M.; Vos, Rutger A.; Doorenweerd, Camiel; Ratnasingham, Sujeevan & Hausmann, Axel [Vis alle 23 forfattere av denne artikkelen] (2016). Species-level para- and polyphyly in DNA barcode gene trees: Strong operational bias in European Lepidoptera. Systematic Biology. ISSN 1063-5157. 65(6), s. 1024–1040. doi: 10.1093/sysbio/syw044. Fulltekst i vitenarkiv
• Lifjeld, Jan Terje; Anmarkrud, Jarl Andreas; Calabuig, Pascual; Cooper, Joseph E.J.; Johannessen, Lars Erik & Johnsen, Arild [Vis alle 12 forfattere av denne artikkelen] (2016). Species-level divergences in multiple functional traits between the two endemic subspecies of Blue Chaffinches Fringilla teydea in Canary Islands. BMC Zoology. doi: 10.1186/s40850-016-0008-4. Fulltekst i vitenarkiv Vis sammendrag

  Background One of the biggest challenges in avian taxonomy is the delimitation of allopatric species because their reproductive incompatibility cannot be directly studied in the wild. Instead, reproductive incompatibility has to be inferred from multiple, divergent character sets that indicate a low likelihood of allopatric populations amalgamating upon secondary contact. A set of quantitative criteria for species delimitation has been developed for avian taxonomy. Results Here, we report a broad multi-trait comparison of the two insular subspecies of the Blue Chaffinch Fringilla teydea, endemic to the pine forests of Tenerife (ssp. teydea) and Gran Canaria (ssp. polatzeki) in the Canary Islands. We found that the two taxa were reciprocally monophyletic in their whole mitogenomes and two Z chromosome introns. The genetic distance in mitogenomes indicates around 1 Mya of allopatric evolution. There were diagnostic differences in body morphometrics, song and plumage reflectance spectra, whose combined divergence score (=11) exceeds the threshold level (=7) set for species delimitation by Tobias et al. (Ibis 152:724–746, 2010). Moreover, we found a marked divergence in sperm lengths with little range overlap. Relatively long sperm with low intra- and intermale CV compared to other passerines suggest a mating system with high levels of sperm competition (extrapair paternity) in these taxa. Conclusion The large and diagnostic divergences in multiple functional traits qualify for species rank, i.e., Tenerife Blue Chaffinch (Fringilla teydea) and Gran Canaria Blue Chaffinch (Fringilla polatzeki). We encourage a wider use of sperm traits in avian taxonomy because sperm divergences might signal reproductive incompatibility at the postcopulatory prezygotic stage, especially in species with sperm competition.

• Støstad, Hanna Nyborg; Rekdal, Silje Larsen; Kleven, Oddmund; Laskemoen, Terje; Marthinsen, Gunnhild & Johnsen, Arild [Vis alle 7 forfattere av denne artikkelen] (2016). Weak geographical structure in sperm morphology across the range of two willow warbler Phylloscopus trochilus subspecies in Scandinavia. Journal of Avian Biology. ISSN 0908-8857. 47(5), s. 731–741. doi: 10.1111/jav.00981. Fulltekst i vitenarkiv Vis sammendrag

  Sperm morphology is highly diversified among species and at higher taxonomic levels. In birds, there is also increasing evidence of geographical differentiation in sperm traits within species, especially in those with strong sperm competition. Geographical divergences in sperm traits might imply the formation of a reproductive barrier in a speciation process. Here we study sperm morphology variation of willow warblers Phylloscopus trochilus in a geographical context in Scandinavia, across the range of two subspecies that are differentiated in certain genetic markers, morphology and migratory routes. We describe geographical patterns in genotypes (two previously described single-nucleotide polymorphism (SNP) markers and four polymorphic microsatellites); in wing length, tarsus length and body mass; and in sperm traits of 330 male willow warblers sampled at 33 localities across Norway (58°N–69°N). Birds were on average larger and longer-winged in the north (spp. acredula) than in the south (spp. trochilus), and showed a sigmoid change in the SNP allele frequencies and body morphology around 65°N. We found no evidence of genetic structuring in the microsatellites. There was no geographical variation in sperm traits across Norway, except that sperm heads were on average longer in the south. Sperm head length was also associated with the two SNP markers, with longer sperm heads for the southern alleles, and midpiece length was weakly associated with one of the SNP markers. Similar among-male variances in total sperm length among the 33 sampling sites indicate uniform levels of sperm competition across Norway. We conclude that sperm morphology remains a rather undifferentiated trait between the two willow warbler subspecies in Scandinavia, which is consistent with a pattern of a shallow genetic divergence. This indicates that sperm morphology is not a reproductive barrier maintaining the narrow hybrid zone.

• Lemoine, Melissa; Lucek, Kay; Perrier, Charles; Saladin, Verena; Adriaensen, Frank & Barba, Emilio [Vis alle 27 forfattere av denne artikkelen] (2016). Low but contrasting neutral genetic differentiation shaped by winter temperature in European great tits. Biological Journal of the Linnean Society. ISSN 0024-4066. 118(3), s. 668–685. doi: 10.1111/bij.12745. Fulltekst i vitenarkiv
• Cramer, Emily Rebecca A; Ålund, Murielle; McFarlane, S. Eryn; Johnsen, Arild & Qvarnström, Anna (2016). Females discriminate against heterospecific sperm in a natural hybrid zone. Evolution. ISSN 0014-3820. 70(8), s. 1844–1855. doi: 10.1111/evo.12986. Fulltekst i vitenarkiv
• Cramer, Emily Rebecca A; Laskemoen, Terje; Stensrud, Even; Rowe, Melissah; Haas, Fredrik & Lifjeld, Jan Terje [Vis alle 8 forfattere av denne artikkelen] (2015). Morphology-function relationships and repeatability in the sperm of Passer sparrows. Journal of morphology. ISSN 0362-2525. 276(4), s. 370–377. doi: 10.1002/jmor.20346. Fulltekst i vitenarkiv
• Boumans, Louis & Johnsen, Arild (2015). Stonefly duets: vibrational sexual mimicry can explain complex patterns. Journal of Ethology. ISSN 0289-0771. 33(2), s. 87–107. doi: 10.1007/s10164-015-0423-y. Fulltekst i vitenarkiv Vis sammendrag

  Stoneflies of the suborder Arctoperlaria exchange vibration signals for intersexual communication. The exchange takes the form of a duet with a male Call and female Answer. Some species and populations have three-way duets, with the male responding to the Answer with a third signal, termed Reply. We review duet descriptions of 106 species in terms of their temporal organisation and mate guarding tactics as identified by Bailey (2003), and propose a functional explanation in terms of concealment of the female for three recurrent phenomena: (1) In the case of large temporal overlap between Call and Answer, the overlapping part of the Call masks the Answer; (2) In three-way duets, the Reply mimics the female; (3) In a Call with two distinct phases, one phase mimics the female. It turns out that the Reply can be interpreted as mimicking the Answer in virtually all three-way duets. In two-way duets with a diphasic Call, the first phase typically mimics the Answer. Three-way duets with a diphasic Call are heterogeneous. Evidence for eavesdropping behaviour comes from the observation that males of the genus Zwicknia produce a Call in response to duetting sequences more often than in response to single male Call signals. We conclude with proposals for further research.

• Hogner, Silje; Riera, Albert Burgas; Wold, Margrethe; Lifjeld, Jan Terje & Johnsen, Arild (2015). Intergeneric hybridization between Common Redstart Phoenicurus phoenicurus and Whinchat Saxicola rubetra revealed by molecular analyses. Journal of Ornithology. ISSN 2193-7192. 156, s. 829–836. doi: 10.1007/s10336-015-1165-x. Fulltekst i vitenarkiv
• Rowe, Melissah; Albrecht, Tomas; Cramer, Emily Rebecca A; Johnsen, Arild; Laskemoen, Terje & Weir, Jason T [Vis alle 7 forfattere av denne artikkelen] (2015). Postcopulatory sexual selection is associated with accelerated evolution of sperm morphology. Evolution. ISSN 0014-3820. 69(4), s. 1044–1052. doi: 10.1111/evo.12620. Fulltekst i vitenarkiv

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• Johnsen, Arild & Nordhus-Kristoffersen, Mathias (2024). Tar DNA-prøver av mossehval. [TV]. NRK Østlandssendingen. Fulltekst i vitenarkiv
• Johnsen, Arild & Nilsen, Torbjørn Tumyr (2024). Fuglearkitektene. [Journal]. Arkitektur. Fulltekst i vitenarkiv
• Johnsen, Arild & Arntsen, Marte Kaasa (2024). Måker (Hadia Tajik). [TV]. NRK Kveldsnytt. Fulltekst i vitenarkiv
• Grøndahl, Finn Audun & Johnsen, Arild (2024). To underarter av storskarv er vanlige i Randsfjorden. Birdlife.no. Fulltekst i vitenarkiv
• Johnsen, Arild & Bjermeland, Monica (2024). Lyden av natur – live på Øyafestivalen 2024. [Internet]. Universitetsplassen. Fulltekst i vitenarkiv
• Johnsen, Arild (2024). Hva forteller fuglenes sang, fjærdrakt og adferd om fuglenes helse? Fulltekst i vitenarkiv
• Vogt, Yngve & Johnsen, Arild (2023). Blåstrupens utroskap bedrer immunforsvaret til avkommet. [Journal]. Apollon. Fulltekst i vitenarkiv
• Melteig, Elina; Johnsen, Arild & Lifjeld, Jan Terje (2023). Far er utro for å få flere barn. Mor er utro for å få bedre barn. [Journal]. Titan.no. Fulltekst i vitenarkiv
• Whittington, Emma; Cramer, Becky; Grønstøl, Gaute; Leder, Erica Helen; Johnsen, Arild & Lifjeld, Jan Terje (2023). Comparative proteomics of the perivitelline layer - the site of avian sperm-egg interaction. Fulltekst i vitenarkiv
• Cramer, Becky & Johnsen, Arild (2022). Why are sperm cells so diverse when they all have the exact same job? sciencenorway.no. Fulltekst i vitenarkiv
• Cramer, Becky & Johnsen, Arild (2022). Hvorfor er sædceller så forskjellige når de alle har den samme enkle oppgaven? https://forskning.no/. Fulltekst i vitenarkiv
• Whittington, Emma; Cramer, Becky; Leder, Erica Helen; Johnsen, Arild & Lifjeld, Jan Terje (2022). Comparative proteomics of the perivitelline layer – the site of avian sperm-egg interaction. Fulltekst i vitenarkiv Vis sammendrag

  Fertilisation requires interaction between the egg and sperm. Miscommunication between the two gametes can lead to incompatibilities, loss of fertility, and failure to produce a viable zygote. Sperm and egg proteins underlying this interaction are a potential post-mating pre-zygotic mechanism of female choice and species recognition. To understand sperm-egg interactions, and how they may contribute to reproductive barriers, we need to identify and explore these proteins across species. Thus far, research in model systems has identified some interacting sperm and egg proteins, including lysin and VERL in abalone, and Izumo1 and Juno in mice. In birds, sperm interact with the membrane surrounding the yolk, the inner perivitelline layer (IPVL). We used a proteomics approach to characterise the IPVL across eight passerine species to identify candidate proteins involved in sperm-egg interactions. Immediately before fertilisation, the sperm membrane weakens, and the contents of the acrosome (a vesicle in the sperm head) are released. Proteins released in this acrosome reaction are in a position to interact with the egg. Two phenomena distinguish avian fertilisation. Firstly, the IPVL is required to induce the acrosome reaction. Secondly, polyspermy is essential for fertilisation. In addition, in passerine birds, sperm length (40-300μm) and acrosome volume (0.48-7.18μm3) varies considerably across species. We take advantage of this natural variation to explore how IPVL protein composition and structure differ across species and how variation in sperm morphology may influence the IPVL and sperm-egg interactions. Our results give insights into avian sperm-egg interaction and proteins that may underlie barriers to hybridisation.

• Bagdonaite, Laima; Lifjeld, Jan Terje; Johnsen, Arild & Leder, Erica Helen (2022). Mitochondrial DNA copy number variation in birds and its relationship to sperm midpiece length. Fulltekst i vitenarkiv Vis sammendrag

  Tremendous variation in sperm morphology is observed across the animal kingdom. In birds, the length of the midpiece, which is formed when several mitochondria fuse during spermatogenesis, explains a considerable amount of this variation. The midpiece is one of the main structural components of the sperm cell and is an important source of energy used for the propulsion of the sperm, mainly generated by oxidative phosphorylation reactions in the fused mitochondria. However, there is still little known about the total number of mitochondria that form the midpiece. In this project, we aim to identify the relationship between the length of the midpiece and the copy number of mitochondrial DNA (mtDNA). To test the hypothesis that sperm with longer midpiece have a higher number of mtDNA, we analyse a range of wild passerine species representing extreme ends of sperm phenotypic variation and major phylogenetic clades within Passerides. We use universal primers to amplify a region of the mitochondrial cytochrome c oxidase subunit I (COI) gene and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a single reference gene for nuclear DNA, and employ quantitative real-time PCR on rinsed sperm samples to measure the relative number of mtDNA copies across species. Our findings will be important for better understanding sperm motility and uncovering the association between sperm midpiece length and mitochondrial loading in wild passerines.

• Rekdal, Silje Larsen; Anmarkrud, Jarl Andreas; Lifjeld, Jan Terje & Johnsen, Arild (2022). MHC-based mate choice in bluethroats. Fulltekst i vitenarkiv
• Johnsen, Arild (2021). MHC-based mate choice in bluethroats. Fulltekst i vitenarkiv
• Johnsen, Arild (2021). Øvre Heimdalen field station - past, present and future. Fulltekst i vitenarkiv
• Cramer, Emily Rebecca Alison; Garcia-del-Rey, Eduardo; Johannessen, Lars Erik; Laskemoen, Terje; Marthinsen, Gunnhild & Johnsen, Arild [Vis alle 7 forfattere av denne artikkelen] (2021). Sperm evolution in the Canary Islands chiffchaff. Fulltekst i vitenarkiv
• Cerca, Jose; Johnsen, Arild; Struck, Torsten H & Bachmann, Lutz (2020). Naturhistoriske samlinger i den molekylære æraen: En kostbar hobby eller en bærebjelke for moderne forskning? Naturen. ISSN 0028-0887. s. 110–116. doi: 10.18261/issn.1504-3118-2020-03-07. Fulltekst i vitenarkiv
• Johnsen, Arild (2020). Female extra-pair mating in birds: is there a universal adaptive explanation? Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Baussant, Thierry; Boer, Hugo de; Carson, Siri Granum & Dahle, Geir [Vis alle 14 forfattere av denne artikkelen] (2020). BIOSCAN Norway - Enabling next generation biodiversity research. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Merkel, Marie Kristine Føreid [Vis alle 8 forfattere av denne artikkelen] (2019). Five years as national research infrastructure: status of the Norwegian Barcode of Life Network (NorBOL). Fulltekst i vitenarkiv
• Johnsen, Arild (2019). Female extra-pair mating in birds: is there a common adaptive explanation? Fulltekst i vitenarkiv
• Marthinsen, Gunnhild & Johnsen, Arild (2019). DNA-strekkoding: genetisk identifisering av arter. Biolog. ISSN 0801-0722. 37(3-4), s. 24–29. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Merkel, Marie Kristine Føreid [Vis alle 8 forfattere av denne artikkelen] (2019). Five years as national research infrastructure: status of the Norwegian Barcode of Life Network (NorBOL). Genome. ISSN 0831-2796. 62(6), s. 369–369. doi: 10.1139/gen-2019-0083. Fulltekst i vitenarkiv
• Johnsen, Arild & Gjesdal, Trine-Lise (2018). Møt en forsker: zoolog Arild Johnsen. [Journal]. Nysgjerrigper. Fulltekst i vitenarkiv
• Torgersen, Eivind & Johnsen, Arild (2018). To ravner er blitt én. [Internet]. Forskning.no. Fulltekst i vitenarkiv
• Ålund, Murielle; Cramer, Emily Rebecca A; McFarlane, Eryn; Johnsen, Arild & Qvarnström, Anna (2017). Females discriminate against heterospecific sperm in a natural hybrid zone. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Kongshavn, Katrine [Vis alle 8 forfattere av denne artikkelen] (2017). The Norwegian Barcode of Life Network (NorBOL). Fulltekst i vitenarkiv
• Marthinsen, Gunnhild; Bendiksby, Mika; Brandrud, Tor Erik; Dima, Bálint; Hansen, Lars Ove & Johnsen, Arild [Vis alle 8 forfattere av denne artikkelen] (2017). Discordance between morphology and DNA barcodes in lichens, fungi and insects. Fulltekst i vitenarkiv
• Johnsen, Arild (2017). Cryptic female choice at the intra- and interspecific level in passerines: what are the molecular mechanisms? Fulltekst i vitenarkiv
• Johnsen, Arild (2017). Utroskap, sjalusi og spermier hos småfugl. Fulltekst i vitenarkiv
• Johnsen, Arild (2017). Sperm competition in birds: from individual to sperm behaviour. Fulltekst i vitenarkiv
• Johnsen, Arild (2017). Speciation reversal in ravens. Fulltekst i vitenarkiv
• Johnsen, Arild (2017). Øvre Heimdalen field station. Summary and future prospects. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Merkel, Marie Kristine Føreid [Vis alle 9 forfattere av denne artikkelen] (2017). Progress and prospects of the Norwegian Barcode of Life Network (NorBOL). Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Merkel, Marie Kristine Føreid [Vis alle 9 forfattere av denne artikkelen] (2017). Progress and prospects of the Norwegian Barcode of Life Network (NorBOL). Genome. ISSN 0831-2796. 60(11), s. 930–930. doi: 10.1139/gen-2017-0209. Fulltekst i vitenarkiv
• Johnsen, Arild (2017). DNA barcoding at NHM. Science and application. Fulltekst i vitenarkiv
• Magnussen, Trude; Søli, Geir Einar Ellefsen; Johnsen, Arild & Kjærandsen, Jostein (2017). DNA barcode libraries - A treasure chest for alpha taxonomy. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Merkel, Marie Kristine Føreid [Vis alle 9 forfattere av denne artikkelen] (2016). The Norwegian Barcode of Life Network (NorBOL). Fulltekst i vitenarkiv
• Johnsen, Arild & Danielsen, Dag Inge (2016). Utroskap blant fluesnappere gir færre hybridfugler. [Internet]. Forskning.no. Fulltekst i vitenarkiv
• Johnsen, Arild (2016). Heimdalen: Bird research and future prospects. Fulltekst i vitenarkiv
• Johnsen, Arild & Rekdal, Silje Larsen (2016). Drifter. [TV]. NRK - Ut i naturen. Fulltekst i vitenarkiv
• Johnsen, Arild (2016). Nå kommer fuglene - møt eksperten og entusiasten. [Radio]. NRK P2 - Ekko helg. Fulltekst i vitenarkiv
• Johnsen, Arild (2015). Using genetic resources in biosystematic research: examples from the NHMO DNA bank. Fulltekst i vitenarkiv
• Johnsen, Arild (2015). The early stages of the speciation process - prezygotic reproductive isolation and diversification in passerines: final report. Fulltekst i vitenarkiv
• Omland, Kevin E.; Kearns, Anna Marika; Restani, Marco; Szabo, Ildiko & Johnsen, Arild (2015). Speciation reversal in Common Ravens: Genomic evidence of the collapse of cryptic lineages in western North America. Fulltekst i vitenarkiv
• Kearns, Anna Marika; Restani, Marco; Szabo, Ildiko; Fleischer, Robert; Johnsen, Arild & Omland, Kevin E. (2015). Speciation reversal in ravens? Evidence for the collapse of cryptic Old World and New World lineages. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Føreid, Marie Kristine [Vis alle 8 forfattere av denne artikkelen] (2015). The Norwegian Barcode of Life Network (NorBOL). Genome. ISSN 0831-2796. 58(5). Fulltekst i vitenarkiv Vis sammendrag

  Background: NorBOL (www.norbol.org) was formed in 2007 as a national network to (i) advance barcoding of Norwegian and Arctic biodiversity, (ii) raise funding, (iii) curate barcode reference material, (iv) coordinate and initiate new barcoding projects, and (v) increase public awareness of DNA barcoding and barcoding results in Norway. NorBOL is a regional node within iBOL, with a particular responsibility for Polar Regions. NorBOL is coordinated by the NTNU University Museum in Trondheim and connects 16 institutions, including all four major natural history museums as well as all major research institutes in Norway. Results: Despite strong support among research institutions, substantial external funding was only first achieved in 2012 through a grant from the Norwegian Biodiversity Information Centre. Further funding was obtained in 2014 from both the Research Council of Norway and the Norwegian Biodiversity Information Centre. Since then, barcoding progress of the Norwegian fauna, flora, and fungi has increased, and the Barcode of Life Data Systems database currently holds more than 42 000 published sequence records (27 000 DNA barcodes) of more than 7200 species from Norway. Significance: The goal for NorBOL is to barcode 20 000 species by the end of 2018. NorBOL currently targets barcoding of museum collections, lichens, fungi, marine invertebrates, fish, and material from biosurveillance projects supported by the Norwegian Taxonomy Initiative. We collaborate with Swedish institutions on sampling of marine invertebrates, earthworms, and insects. An expansion of inter-Scandinavian barcoding collaboration is in progress. As the standard barcode gene regions have limited taxonomic resolution for the species level in many vascular plant groups, we are engaged in testing if low-coverage shotgun sequencing of herbarium material is useful to obtain the full plant plastid genomes.

• Cramer, Emily Rebecca A; Ålund, Murielle; McFarlane, S. Eryn; Johnsen, Arild & Qvarnström, Anna (2015). A post-copulatory pre-zygotic barrier between collared and pied flycatchers. Fulltekst i vitenarkiv
• Ekrem, Torbjørn; Alsos, Inger Greve; Johnsen, Arild; Willassen, Endre; Aspaas, Aina Mærk & Føreid, Marie Kristine [Vis alle 8 forfattere av denne artikkelen] (2015). The Norwegian Barcode of Life Network (NorBOL). Fulltekst i vitenarkiv Vis sammendrag

  Background: NorBOL (www.norbol.org) was formed in 2007 as a national network to (i) advance barcoding of Norwegian and Arctic biodiversity, (ii) raise funding, (iii) curate barcode reference material, (iv) coordinate and initiate new barcoding projects, and (v) increase public awareness of DNA barcoding and barcoding results in Norway. NorBOL is a regional node within iBOL, with a particular responsibility for Polar Regions. NorBOL is coordinated by the NTNU University Museum in Trondheim and connects 16 institutions, including all four major natural history museums as well as all major research institutes in Norway. Results: Despite strong support among research institutions, substantial external funding was only first achieved in 2012 through a grant from the Norwegian Biodiversity Information Centre. Further funding was obtained in 2014 from both the Research Council of Norway and the Norwegian Biodiversity Information Centre. Since then, barcoding progress of the Norwegian fauna, flora, and fungi has increased, and the Barcode of Life Data Systems database currently holds more than 42 000 published sequence records (27 000 DNA barcodes) of more than 7200 species from Norway. Significance: The goal for NorBOL is to barcode 20 000 species by the end of 2018. NorBOL currently targets barcoding of museum collections, lichens, fungi, marine invertebrates, fish, and material from biosurveillance projects supported by the Norwegian Taxonomy Initiative. We collaborate with Swedish institutions on sampling of marine invertebrates, earthworms, and insects. An expansion of inter-Scandinavian barcoding collaboration is in progress. As the standard barcode gene regions have limited taxonomic resolution for the species level in many vascular plant groups, we are engaged in testing if low-coverage shotgun sequencing of herbarium material is useful to obtain the full plant plastid genomes.

• Finstad, Anders Gravbrøt; Boer, Hugo de; Brurberg, May Bente; Dahle, Geir; Edgar, Kristin Skarsfjord & Eiler, Alexander [Vis alle 25 forfattere av denne artikkelen] (2020). Kriterier for lagring av miljø-DNA prøver og data, herunder henvisning til referansemateriale. Criteria for depositing eDNA samples and data, including vouchered specimens. Miljødirektoratet. Fulltekst i vitenarkiv

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