Siri Birkeland

• Rodriguez, Eduardo; Birkeland, Siri; Chapple, Ellen Dimmen; Fredriksson, Samuel Nils Andreas; Lorenzo, Zulema Carracedo & Kalman, Teitur Ahlgren [Show all 16 contributors for this article] (2026). Comparative regulomics of wood formation across dicot and conifer trees. Nature Communications. 17(1). doi: 10.1038/s41467-026-75624-2. Full text in Research Archive
• Birkeland, Siri; Soldado, Eduardo R.; Ranade, Sonali S.; García-Gil, M. Rosario; Choudhary, Shruti & Kumar, Vikash [Show all 10 contributors for this article] (2025). An updated perspective: what genes make a tree a tree? Trends in Plant Science. ISSN 1360-1385. 31(1), p. 20–31. doi: 10.1016/j.tplants.2025.09.006. Full text in Research Archive Show summary

  We learn early on how to tell trees apart from other plants. However, it has proved hard to distinguish trees from other plants at the genetic level, and it is believed that there are no unique ‘tree genes’. With the rapid increase in available tree genomes, we can perform new comparative and evolutionary analyses of plant life histories and growth forms. Here we provide a fresh perspective on the genetic foundation for woodiness and perenniality in angiosperms by analyzing selection pressures and gene family evolution in the rosids using genomic data. We examine genes distinguishing trees from herbs and discuss future directions for uncovering the genetic factors that define a tree in this new era of tree genomics.

• Brochmann, Christian; Elphinstone, Cassandra; Birkeland, Siri; Ikeda, Hajime; Eidesen, Pernille Bronken & Alsos, Inger G. [Show all 7 contributors for this article] (2025). Phylogeography of Arctic plants: where are we after 35 years, and where to go? Plant Ecology & Diversity. ISSN 1755-0874. 18(3-4), p. 99–123. doi: 10.1080/17550874.2025.2571098. Full text in Research Archive Show summary

  Background The Arctic provides an excellent system to study climate change effects on geographic ranges and genetic diversity. We re-examine the large number of phylogeographic studies of Arctic plants to assess general patterns and identify knowledge gaps. Aims To synthesise advances and address century-old controversies, e.g. is it necessary to invoke separate glacial refugia to explain Arctic disjunctions? Methods We undertook a literature survey of the phylogeography of Arctic vascular plants. Results We provide a list of 88 taxa studied, representing a striking diversity of phylogeographic histories. In many widespread species, recent trans-oceanic long-distance dispersal (LDD) is sufficient to explain disjunctions, but three rare species show clear signals of separate Scandinavian and American glacial refugia. The extreme bipolar disjunctions are apparently caused by Plio-Pleistocene LDDs. Beringia and western Siberia have served as long-standing northern refugia; in contrast, North Atlantic areas harbour much less genetic diversity and distinctiveness. The genomic era is now providing evidence for multiple refugia from modern and ancient DNA and demonstrating that selfing leads to high biological species diversity within taxonomically recognised species. Conclusions More extensive sampling, reference genomes, and population genomic studies are required for in-depth understanding of past distributions, dispersal routes, and ability to track ongoing climate change.

• Moreyra, Lucía D.; Calleja, Juan Antonio; Roquet, Cristina; Birkeland, Siri; Blanco‐Gavaldà, Carme & Galbany‐Casals, Mercè [Show all 10 contributors for this article] (2025). Hidden lineages in the African Sky Islands: A taxonomic reevaluation of Afrocarduus (Compositae). Journal of Systematics and Evolution. ISSN 1674-4918. doi: 10.1111/jse.70024. Full text in Research Archive Show summary

  Accurate species delimitation is crucial for biodiversity research, as it significantly impacts taxonomy, ecology, and conservation. Recent advances in molecular phylogenetics and integrative taxonomy have improved classifications and resolved long‐standing taxonomic uncertainties. Here, we use Hyb‐Seq (489 nuclear loci) and phylogenomic approaches to investigate Afrocarduus , a genus endemic to tropical Afromontane and Afroalpine regions. Our analyses reveal 16 evolutionary lineages within this relatively young genus (crown age 2.3 Mya), with new morphological data strongly supporting the recognition of each lineage as a distinct species. We demonstrate that the stemless habit evolved independently in species from the Ethiopian Highlands and the East African Rift System (EARS). Notably, we show that the concept of the stemless Afrocarduus schimperi adopted by the Flora of Tropical East Africa, in fact, comprises seven clearly recognizable species, which we formally reinstate. Unexpectedly, the stemmed Afrocarduus nyassanus was recovered as paraphyletic with Afrocarduus ruwenzoriensis nested within it, probably due to incomplete lineage sorting or hybridization. Additionally, the stemmed Afrocarduus keniensis may represent a complex of cryptic species, and we describe a new stemmed species from southern Ethiopia, Afrocarduus kazmi sp. nov. We expand the number of accepted species in Afrocarduus from eight, as recognized in the Flora of Tropical East Africa, to 18 (including two species for which we were not able to obtain molecular data). Our study thus highlights a substantial prior underestimation of the diversity of Afrocarduus in Afromontane and Afroalpine habitats.

• Moreyra, Lucía D.; Roquet, Cristina; Susanna, Alfonso; Birkeland, Siri; Blanco‐Gavaldà, Carme & Brochmann, Christian [Show all 10 contributors for this article] (2025). From Pleistocene Corridors to Isolated Peaks and Back: Biogeography of Afrocarduus (Compositae) in the Afromontane Archipelago. Journal of Biogeography. ISSN 0305-0270. 52(11). doi: 10.1111/jbi.70045. Full text in Research Archive Show summary

  Aim We investigated the biogeographic history and diversification dynamics of Afrocarduus, an Afromontane–Afroalpine genus endemic to eastern Africa. We aimed to assess the roles of geographic isolation, habitat transitions, and ecological speciation in shaping current diversity. Location The Afromontane and Afroalpine regions of East Africa and Ethiopia are situated along the Great Rift Valley system. Taxon Afrocarduus (Compositae: Carduinae), a genus comprising 18 endemic species. Methods We conducted a comprehensive taxonomic and geographic sampling of Afrocarduus, generating data from 489 nuclear loci. Phylogenomic and biogeographic ancestral estimation analyses were performed to infer the evolutionary history and historical biogeography of the genus. Results Afrocarduus originated in the Afromontane zone of eastern Africa during the Late Miocene (~10.7 Ma), with major diversification events occurring in the Early Pleistocene (~2.3 Ma). Most dispersal events occurred between neighbouring massifs, though occasional long-distance dispersal between disjunct mountain systems was detected. The Turkana Depression and the Great Rift Valley have acted as major biogeographic barriers. Phylogenetic structure shows distinct clades occupying different regions. Ecological divergence between Afromontane and Afroalpine environments contributed to speciation, with at least six independent adaptations to Afroalpine conditions and multiple cases of ecological reversal. Stem loss, a trait associated with alpine habitats, evolved convergently in two clades. Closely related species often segregate by elevation or microhabitat within the same massif. Main Conclusions The diversification of Afrocarduus has been shaped by a combination of historical climate change, geographic isolation, and ecological adaptation. Our results emphasise the importance of ecological speciation and habitat transitions in Afrotemperate plant evolution and highlight the need for further research on understudied Afromontane taxa, especially under the threat of ongoing climate change.

• Hoitinga, Peter K. & Birkeland, Siri (2025). Pathway-level convergence: an underexplored aspect of convergent evolution. Trends in Genetics. ISSN 0168-9525. 41(10), p. 853–867. doi: 10.1016/j.tig.2025.06.009. Full text in Research Archive Show summary

  The extent to which evolution is repeatable at the genetic level remains a central question in biology. Convergent adaptations can arise through mutations in homologous genes, changes in different genes within the same pathways, or distinct molecular routes. Most research has focused on gene-level convergence, whereas relatively little is known about the prevalence of pathway-level convergence. Here, we synthesize theoretical perspectives on pathway-level convergence, focusing on how genetic complexity of a trait and divergence time between taxa shape the likelihood of convergence at the pathway versus gene level. We highlight methodological considerations and argue that integration with systems biology is critical for advancing the field. We aim to stimulate more hypothesis-driven research into the mechanisms and prevalence of pathway-level convergence.

• Scharwies, Johannes D.; Clarke, Taylor; Zheng, Zihao; Dinneny, Andrea; Birkeland, Siri & Veltman, Margret [Show all 16 contributors for this article] (2025). Moisture-responsive root-branching pathways identified in diverse maize breeding germplasm. Science. ISSN 0036-8075. 387(6734), p. 666–673. doi: 10.1126/science.ads5999. Full text in Research Archive
• Sartorius, Alina Marie; Rokicki, Jaroslav; Birkeland, Siri; Bettella, Francesco; Barth, Claudia & Lange, Ann-Marie Glasø de [Show all 17 contributors for this article] (2024). An evolutionary timeline of the oxytocin signaling pathway. Communications Biology. 7(1). doi: 10.1038/s42003-024-06094-9. Full text in Research Archive Show summary

  Oxytocin is a neuropeptide associated with both psychological and somatic processes like parturition and social bonding. Although oxytocin homologs have been identified in many species, the evolutionary timeline of the entire oxytocin signaling gene pathway has yet to be described. Using protein sequence similarity searches, microsynteny, and phylostratigraphy, we assigned the genes supporting the oxytocin pathway to different phylostrata based on when we found they likely arose in evolution. We show that the majority (64%) of genes in the pathway are ‘modern’. Most of the modern genes evolved around the emergence of vertebrates or jawed vertebrates (540 - 530 million years ago, ‘mya’), including OXTR, OXT and CD38. Of those, 45% were under positive selection at some point during vertebrate evolution. We also found that 18% of the genes in the oxytocin pathway are ‘ancient’, meaning their emergence dates back to cellular organisms and opisthokonta (3500–1100 mya). The remaining genes (18%) that evolved after ancient and before modern genes were classified as ‘medium-aged’. Functional analyses revealed that, in humans, medium-aged oxytocin pathway genes are highly expressed in contractile organs, while modern genes in the oxytocin pathway are primarily expressed in the brain and muscle tissue.

• Marie-Orleach, Lucas; Glémin, Sylvain; Brandrud, Marie Kristine; Brysting, Anne Krag; Seid, Abel Gizaw & Gustafsson, A Lovisa S [Show all 9 contributors for this article] (2024). How Does Selfing Affect the Pace and Process of Speciation? Cold Spring Harbor Perspectives in Biology. 16(11). doi: 10.1101/cshperspect.a041426. Full text in Research Archive Show summary

  Surprisingly little attention has been given to the impact of selfing on speciation, even though selfing reduces gene flow between populations and affects other key population genetics parameters. Here we review recent theoretical work and compile empirical data from crossing experiments and genomic and phylogenetic studies to assess the effect of mating systems on the speciation process. In accordance with theoretical predictions, we find that accumulation of hybrid incompatibilities seems to be accelerated in selfers, but there is so far limited empirical support for a predicted bias toward underdominant loci. Phylogenetic evidence is scarce and contradictory, including studies suggesting that selfing either promotes or hampers speciation rate. Further studies are therefore required, which in addition to measures of reproductive barrier strength and selfing rate should routinely include estimates of demographic history and genetic divergence as a proxy for divergence time.

• Hämälä, Tuomas; Moore, Christopher; Cowan, Laura; Carlile, Matthew; Gopaulchan, David & Brandrud, Marie Kristine [Show all 11 contributors for this article] (2024). Impact of whole-genome duplications on structural variant evolution in Cochlearia. Nature Communications. 15(1). doi: 10.1038/s41467-024-49679-y. Full text in Research Archive Show summary

  Polyploidy, the result of whole-genome duplication (WGD), is a major driver of eukaryote evolution. Yet WGDs are hugely disruptive mutations, and we still lack a clear understanding of their fitness consequences. Here, we study whether WGDs result in greater diversity of genomic structural variants (SVs) and how they influence evolutionary dynamics in a plant genus, Cochlearia (Brassicaceae). By using long-read sequencing and a graph-based pangenome, we find both negative and positive interactions between WGDs and SVs. Masking of recessive mutations due to WGDs leads to a progressive accumulation of deleterious SVs across four ploidal levels (from diploids to octoploids), likely reducing the adaptive potential of polyploid populations. However, we also discover putative benefits arising from SV accumulation, as more ploidy-specific SVs harbor signals of local adaptation in polyploids than in diploids. Together, our results suggest that SVs play diverse and contrasting roles in the evolutionary trajectories of young polyploids.

• Hamala, Tuomas; Moore, Christopher; Cowan, Laura; Carlile, Matthew; Gopaulchan, David & Brandrud, Marie Kristine [Show all 11 contributors for this article] (2023). Impact of whole-genome duplications on structural variant evolution in the plant genus Cochlearia. BioRxiv. ISSN 0362-4331. Full text in Research Archive
• Birkeland, Siri (2022). To what degree does hybridization facilitate evolutionary radiations in mountain areas? National Science Review. ISSN 2095-5138. 9(nwac288). Full text in Research Archive
• Cerca, José; Petersen, Bent; Lazaro-Guevara, José Miguel; Rivera-Colón, Angel G.; Birkeland, Siri & Vizueta, Joel [Show all 29 contributors for this article] (2022). The genomic basis of the plant island syndrome in Darwin’s giant daisies. Nature Communications. 13. doi: 10.1038/s41467-022-31280-w. Full text in Research Archive Show summary

  The repeated, rapid and often pronounced patterns of evolutionary divergence observed in insular plants, or the ‘plant island syndrome’, include changes in leaf phenotypes, growth, as well as the acquisition of a perennial lifestyle. Here, we sequence and describe the genome of the critically endangered, Galápagos-endemic species Scalesia atractyloides Arnot., obtaining a chromosome-resolved, 3.2-Gbp assembly containing 43,093 candidate gene models. Using a combination of fossil transposable elements, k-mer spectra analyses and orthologue assignment, we identify the two ancestral genomes, and date their divergence and the polyploidization event, concluding that the ancestor of all extant Scalesia species was an allotetraploid. There are a comparable number of genes and transposable elements across the two subgenomes, and while their synteny has been mostly conserved, we find multiple inversions that may have facilitated adaptation. We identify clear signatures of selection across genes associated with vascular development, growth, adaptation to salinity and flowering time, thus finding compelling evidence for a genomic basis of the island syndrome in one of Darwin’s giant daisies.

• Birkeland, Siri; Slotte, Tanja; Brysting, Anne Krag; Gustafsson, Lovisa; Hvidsten, Torgeir Rhoden & Brochmann, Christian [Show all 7 contributors for this article] (2022). What can cold-induced transcriptomes of Arctic Brassicaceae tell us about the evolution of cold tolerance? Molecular Ecology. ISSN 0962-1083. 31(16), p. 4271–4285. doi: 10.1111/mec.16581. Full text in Research Archive Show summary

  Little is known about the evolution of cold tolerance in polar plant species and how they differ from temperate relatives. To gain insight into their biology and the evolution of cold tolerance, we compared the molecular basis of cold response in three Arctic Brassicaceae species. We conducted a comparative time series experiment to examine transcriptional responses to low temperature. RNA was sampled at 22°C, and after 3, 6, and 24 at 2°C. We then identified sets of genes that were differentially expressed in response to cold and compared them between species, as well as to published data from the temperate Arabidopsis thaliana. Most differentially expressed genes were species-specific, but a significant portion of the cold response was also shared among species. Among thousands of differentially expressed genes, ~200 were shared among the three Arctic species and A. thaliana, while ~100 were exclusively shared among the three Arctic species. Our results show that cold response differs markedly between Arctic Brassicaceae species, but probably builds on a conserved basis found across the family. They also confirm that highly polygenic traits such as cold tolerance may show little repeatability in their patterns of adaptation.

• Nowak, Michael; Birkeland, Siri; Mandáková, Terezie; Choudhury, Rimjhim Roy; Guo, Xinyi & Gustafsson, A Lovisa S [Show all 15 contributors for this article] (2020). The genome of Draba nivalis shows signatures of adaptation to the extreme environmental stresses of the Arctic. Molecular Ecology Resources. ISSN 1755-098X. doi: 10.1111/1755-0998.13280. Full text in Research Archive
• Birkeland, Siri; Gustafsson, A Lovisa S; Brysting, Anne Krag; Brochmann, Christian & Nowak, Michael (2020). Multiple Genetic Trajectories to Extreme Abiotic Stress Adaptation in Arctic Brassicaceae. Molecular Biology and Evolution (MBE). ISSN 0737-4038. 37(7), p. 2052–2068. doi: 10.1093/molbev/msaa068. Full text in Research Archive Show summary

  Abstract Extreme environments offer powerful opportunities to study how different organisms have adapted to similar selection pressures at the molecular level. Arctic plants have adapted to some of the coldest and driest biomes on Earth and typically possess suites of similar morphological and physiological adaptations to extremes in light and temperature. Here, we compare patterns of molecular evolution in three Brassicaceae species that have independently colonized the Arctic and present some of the first genetic evidence for plant adaptations to the Arctic environment. By testing for positive selection and identifying convergent substitutions in orthologous gene alignments for a total of 15 Brassicaceae species, we find that positive selection has been acting on different genes, but similar functional pathways in the three Arctic lineages. The positively selected gene sets identified in the three Arctic species showed convergent functional profiles associated with extreme abiotic stress characteristic of the Arctic. However, there was little evidence for independently fixed mutations at the same sites and for positive selection acting on the same genes. The three species appear to have evolved similar suites of adaptations by modifying different components in similar stress response pathways, implying that there could be many genetic trajectories for adaptation to the Arctic environment. By identifying candidate genes and functional pathways potentially involved in Arctic adaptation, our results provide a framework for future studies aimed at testing for the existence of a functional syndrome of Arctic adaptation in the Brassicaceae and perhaps flowering plants in general.

• Birkeland, Siri; Skjetne, Idunn Elisabeth Borgen; Brysting, Anne Krag; Elven, Reidar & Alsos, Inger Greve (2017). Living on the edge: conservation genetics of seven thermophilous plant species in a high Arctic archipelago. AoB Plants. 9(1). doi: 10.1093/aobpla/plx001. Full text in Research Archive Show summary

  Small, isolated and/or peripheral populations are expected to harbour low levels of genetic variation and may therefore have reduced adaptability to environmental change, including climate warming. In the Arctic, global warming has already caused vegetation change across the region and is acting as a significant stressor on Arctic biodiversity. Many of the rare plants in the Arctic are relicts from early Holocene warm periods, but their ability to benefit from the current warming is dependent on the viability of their populations. We therefore examined Amplified Fragment Length Polymorphism (AFLP) data from regional red listed vascular plant species in the High Arctic archipelago of Svalbard and reference populations from the main distribution area of: (1) Botrychium lunaria, (2) Carex capillaris ssp. fuscidula, (3) Comastoma tenellum, (4) Kobresia simpliciuscula ssp. subholarctica, (5) Ranunculus wilanderi, (6) Sibbaldia procumbens and (7) Tofieldia pusilla. In addition, we gathered population size data in Svalbard. The Svalbard populations had low genetic diversity and distinctiveness and few or no private markers compared to populations outside the archipelago. This is similar to observations in other rare species in Svalbard and the genetic depletion may be due to an initial founder effect and/or a genetic bottleneck caused by late Holocene cooling. There seems to be limited gene flow from other areas and the Svalbard populations should therefore be considered as demographically independent management units. Overall, these management units have small and/or few populations and are therefore prone to stochastic events which may further increase vulnerability to inbreeding depression, loss of genetic variation, and reduced evolutionary potential. Our results support theory predicting lower levels of genetic diversity in small, isolated and/or peripheral populations and may be of importance for management of other rare plant species in the Arctic.

• Struck, Torsten H; Feder, Jeffrey L.; Bendiksby, Mika; Birkeland, Siri; Oliveira, Josè Cerca De & Gusarov, Vladimir [Show all 13 contributors for this article] (2017). Finding Evolutionary Processes Hidden in Cryptic Species. Trends in Ecology & Evolution. ISSN 0169-5347. 33(3), p. 153–163. doi: 10.1016/j.tree.2017.11.007. Full text in Research Archive Show summary

  Cryptic species could represent a substantial fraction of biodiversity. However, inconsistent definitions and taxonomic treatment of cryptic species prevent informed estimates of their contribution to biodiversity and impede our understanding of their evolutionary and ecological significance. We propose a conceptual framework that recognizes cryptic species based on their low levels of phenotypic (morphological) disparity relative to their degree of genetic differentiation and divergence times as compared to non-cryptic species. We discuss how application of a more rigorous definition of cryptic species in taxonomic practice will lead to more accurate estimates of their prevalence in nature, better understanding of their distribution patterns on the tree of life, and increased abilities to resolve the processes underlying their evolution.

• Alsos, Inger Greve; Ehrich, Dorothee; Eidesen, Pernille Bronken; Solstad, Heidi Merethe; Westergaard, Kristine Bakke & Schonswetter, Peter [Show all 10 contributors for this article] (2015). Long-distance plant dispersal to North Atlantic islands: colonization routes and founder effect. AoB Plants. 7(1), p. 1–19. doi: 10.1093/aobpla/plv036. Full text in Research Archive Show summary

  Long-distance dispersal (LDD) processes influence the founder effect on islands.We use genetic data for 25 Atlantic species and similarities among regional floras to analyse colonization, and test whether the genetic founder effect on five islands is associated with dispersal distance, island size and species traits. Most species colonized postglacially via multiple dispersal events from several source regions situated 280 to .3000 km away, and often not from the closest ones. A strong founder effect was observed for insect-pollinated mixed maters, and it increased with dispersal distance and decreased with island size in accordance with the theory of island biogeography. Only a minor founder effect was observed for wind-pollinated outcrossing species. Colonization patterns were largely congruent, indicating that despite the importance of stochasticity, LDD is mainly determined by common factors, probably dispersal vectors. Our findings caution against a priori assuming a single, close source region in biogeographic analyses. Amplified fragment length polymorphism (AFLP); dispersal vector; founder effect; genetic diversity; islands; long-distance dispersal (LDD); postglacial; species traits.

• Westengen, Ola Tveitereid; Okongo, Mark Atam; Onek, Leo; Berg, Trygve; Upadhyaya, Hari & Birkeland, Siri [Show all 10 contributors for this article] (2014). Ethnolinguistic structuring of sorghum genetic diversity in Africa and the role of local seed systems. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 111(39), p. 14100–14105. doi: 10.1073/pnas.1401646111. Full text in Research Archive Show summary

  Sorghum is a drought-tolerant crop with a vital role in the livelihoods of millions of people in marginal areas. We examined genetic structure in this diverse crop in Africa. On the continentwide scale, we identified three major sorghum populations (Central, Southern, and Northern) that are associated with the distribution of ethnolinguistic groups on the continent. The codistribution of the Central sorghum population and the Nilo-Saharan language family supports a proposed hypothesis about a close and causal relationship between the distribution of sorghum and languages in the region between the Chari and the Nile rivers. The Southern sorghum population is associated with the Bantu languages of the Niger-Congo language family, in agreement with the farminglanguage codispersal hypothesis as it has been related to the Bantu expansion. The Northern sorghum population is distributed across early Niger-Congo and Afro-Asiatic language family areas with dry agroclimatic conditions. At a finer geographic scale, the genetic substructure within the Central sorghum population is associated with language-group expansions within the Nilo-Saharan language family. A case study of the seed system of the Pari people, a Western-Nilotic ethnolinguistic group, provides a window into the social and cultural factors involved in generating and maintaining the continent-wide diversity patterns. The age-grade system, a cultural institution important for the expansive success of this ethnolinguistic group in the past, plays a central role in the management of sorghum landraces and continues to underpin the resilience of their traditional seed system.

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• Birkeland, Siri & Hvidsten, Torgeir Rhoden (2025). Trærnes evolusjon: Bjørk er nærmere i slekt med agurk enn grantre. Forskersonen.no. doi: https:/www.forskersonen.no/genetikk-meninger-natur/en-bjork-er-i-naermere-slekt-med-en-agurk-enn-med-et-grantre/2592783. Full text in Research Archive Show summary

  POPULÆRVITENSKAP: Trær som konsept er gammelt. Virkelig gammelt. Gjennom evolusjonen har treformen oppstått flere ganger på ulike greiner av livets tre og like ofte forsvunnet, skriver innsenderne.

• Marie-Orleach, Lucas; Glémin, Sylvain; Brandrud, Marie Kristine; Brysting, Anne Krag; Gustafsson, Lovisa & Seid, Abel Gizaw [Show all 9 contributors for this article] (2024). How does selfing affect the pace and process of speciation? Full text in Research Archive
• Birkeland, Siri (2024). Kaktusfamilien. Full text in Research Archive
• Birkeland, Siri (2023). What drives the rapid evolution of reproductive isolation in Arctic plants? Full text in Research Archive
• Birkeland, Siri (2023). Adaptation and Speciation in Arctic Extremophile Plants. Full text in Research Archive
• Birkeland, Siri; Gustafsson, A Lovisa S; Gizaw, Abel; Chala, Desalegn; Fraccasetti, Marco & Brazier, Thomas [Show all 13 contributors for this article] (2022). What drives the rapid buildup of sterility barriers in the Arctic crucifer Draba nivalis? Full text in Research Archive
• Birkeland, Siri; Soldado, Eduardo Rodriguez; Vandepoele, Klaas; Carracedo, Zulema; Street, Nathaniel R. & Hvidsten, Torgeir Rhoden (2022). What makes a tree a tree? Evolution of the gene regulatory network underlying wood formation. Full text in Research Archive
• Birkeland, Siri & Delsett, Lene Liebe (2021). Tøyen kan ikke vente lenger. Dagsavisen. ISSN 1503-2892. Full text in Research Archive
• Danielsen, Dag Inge & Birkeland, Siri (2021). Hun avdekker arktiske planters frosne hemmeligheter. [Journal]. Titan.uio.no. Full text in Research Archive
• Birkeland, Siri; Slotte, Tanja; Brochmann, Christian; Brysting, Anne Krag; Gustafsson, Lovisa & Nowak, Michael D (2021). What can the cold-induced transcriptomes of Arctic Brassicaceae tell us about the evolution of cold tolerance? Full text in Research Archive
• Danielsen, Dag Inge & Birkeland, Siri (2021). Hvordan klarer plantene seg i ekstrem kulde i Arktis? [Journal]. Forskning.no. Full text in Research Archive
• Birkeland, Siri; Gustafsson, A Lovisa S; Brysting, Anne Krag; Brochmann, Christian & Nowak, Michael (2019). Same destination, but different roads? Overarching, but limited fine-scale molecular convergence in Arctic crucifers. Full text in Research Archive
• Struck, Torsten H; Feder, Jeffrey L.; Bendiksby, Mika; Birkeland, Siri; Oliveira, Josè Cerca De & Gusarov, Vladimir [Show all 13 contributors for this article] (2018). Cryptic Species – More Than Terminological Chaos: A Reply to Heethoff. Trends in Ecology & Evolution. ISSN 0169-5347. 33(5), p. 310–312. doi: 10.1016/j.tree.2018.02.008. Full text in Research Archive
• Nowak, Michael; Gustafsson, A Lovisa S; Birkeland, Siri; Gizaw, Abel; Rieseberg, Loren & Slotte, Tanja [Show all 7 contributors for this article] (2018). Has historical introgression impacted the evolution of hybrid incompatibilities between populations of the Arctic plant Draba nivalis (Brassicaceae)? Full text in Research Archive
• Gustafsson, A Lovisa S; Gizaw, Abel; Birkeland, Siri; Nowak, Michael; Gelete, Desalegn Chala & Slotte, Tanja [Show all 8 contributors for this article] (2018). Evolution of postzygotic reproductive isolation in Arctic and Mediterranean plants. Full text in Research Archive
• Birkeland, Siri; Gustafsson, A Lovisa S; Brysting, Anne Krag; Brochmann, Christian & Nowak, Michael (2018). Testing for convergent signatures of selection in Arctic plants. Full text in Research Archive
• Birkeland, Siri (2018). Hvordan har tre ulike plantearter tilpasset seg et liv i Arktis? Forskning.no. ISSN 1891-635X. Full text in Research Archive
• Oliveira, José Cerca de; Birkeland, Siri; Magnussen, Trude & Kistenich, Sonja Daniela (2017). Forskere krangler om kryptiske arter. Forskning.no. ISSN 1891-635X. Full text in Research Archive
• Støstad, Hanna Nyborg; Birkeland, Siri; Delsett, Lene Liebe & Rosing-Schow, Nanna (2017). Fire råd til deg som vil knuse glasstaket. Full text in Research Archive
• Nowak, Michael; Gustafsson, A Lovisa S; Seid, Abel Gizaw; Birkeland, Siri; Rieseberg, Loren & Slotte, Tanja [Show all 7 contributors for this article] (2017). SpArc: Searching for genetic mechanisms of plant speciation in the Arctic. Full text in Research Archive
• Gustafsson, A Lovisa S; Birkeland, Siri; Gizaw, Abel; Rieseberg, LH; Slotte, Tanja & Nowak, Michael [Show all 7 contributors for this article] (2017). Searching for genetic mechanisms of plant speciation in the Arctic. Full text in Research Archive
• Birkeland, Siri (2017). Hvordan jobber man som en forsker? SpArc-prosjektet som eksempel. Full text in Research Archive
• Birkeland, Siri; Gustafsson, A Lovisa S; Slotte, Tanja; Brysting, Anne Krag; Brochmann, Christian & Nowak, Michael (2017). Testing for convergent molecular evolution in Arctic plants. Full text in Research Archive
• Birkeland, Siri (2017). Lab-prosjekt for biologiklasse basert på SpArc (pollensterilitet hos Draba nivalis-hybrider). Full text in Research Archive
• Birkeland, Siri (2016). Hvordan jobber man som en forsker? SpArc-prosjektet som eksempel. Full text in Research Archive
• Birkeland, Siri; Gustafsson, A Lovisa S; Brysting, Anne Krag; Slotte, Tanja; Brochmann, Christian & Nowak, Michael (2016). Testing for convergent evolution of cold tolerance in Arctic plants. Full text in Research Archive
• Brysting, Anne Krag; Birkeland, Siri & Khalsa, Siri-Dharma Kaur (2012). Eksotiske frukter. Full text in Research Archive
• Fredriksson, Samuel Nils Andreas; Birkeland, Siri; Street, Nathaniel & Hvidsten, Torgeir Rhoden (2024). Regulatory networks in trees. Norges miljø- og biovitenskapelige universitet (NMBU). Full text in Research Archive Show summary

  Network analysis involves examining pairwise interactions between individual elements, in the current study genes and proteins. Unlike traditional data analysis methods that focus on individual elements, network analysis is an holistic approach that emphasizes the relationships among all elements and in- vestigates their collective behavior. Here, transcription factors (TFs) of importance in wood formation are identified and examined by looking at specific TF binding motifs (TF motifs) that are enriched in the regulatory promoter regions upstream of genes involved in secondary growth (i.e. wood develop- ment). The enriched TFs provided TF-gene links for inference of gene regulatory networks (GRNs) underlying wood formation in Populus tremula (a seed plant; Angiosperm) and Picea abies (a conifer; Gymnosperm). Multi-omics data (Co-expression and physical protein-protein interactions) of regulator and target genes in TF-gene links and hierarchical TF-TF links unraveled novel NAC and MYB master regulators, homologs of regulators in the non-woody model organism Arabidopsis thaliana, (At) and their NAC-MYB-based gene regulatory network (GRN). These pathways have been proposed to be conserved for the regulation of secondary cell wall (SCW) biosynthesis between herbaceous At and woody plants (Taylor-Teeples et al., 2015), (Li et al., 2024). Our network comparison revealed conserved network motifs in the GRNs of conifers and angiosperms that control SCW genes. This suggests that functional roles have been retained despite > 200 million years of evolutionary divergence between the two lineages and significant anatomical differences in both cell type and cell wall components. Our findings of master regulators represent potential biomarkers for secondary growth in trees and provide natural targets for future functional characterisation studies.

• Birkeland, Siri (2020). Tracing Molecular Patterns of Adaptation in Arctic Brassicaceae: Evolutionary repeatability and adaptations to extreme abiotic stress. Universitetet i Oslo. Full text in Research Archive Show summary

  A central objective of evolutionary biology is to understand how organisms adapt to novel environments, and to what degree this process follows repeatable patterns. This thesis explores how three Arctic plant species evolved to live in some of the coldest biomes on Earth, and how they developed similar adaptations to extreme light and temperature conditions. It consists of three complementary studies, whereof the first compares patterns of molecular evolution, the second examines how Arctic plants respond to cold, and the third presents the first genome assembly of an Arctic plant. The main finding is that the three species appear to have evolved similar suites of adaptations by modifying different components in similar stress response pathways, implying that there could be many genetic trajectories for adaptation to the Arctic environment. This lack of evolutionary repeatability differs from similar studies on other plant genera. The thesis represents the first molecular study of Arctic plant adaptations, and provides both a framework and the tools (in form of a genome assembly) for more in depth studies on the molecular ecology of Arctic plants.

• Alsos, Inger Greve; Elven, Reidar; Brysting, Anne Krag; Birkeland, Siri & Skjetne, Idunn Elisabeth Borgen (2011). Økologiske og genetiske undersøkelser av rødlistearter på Svalbard. Svalbard miljøvernfond. Full text in Research Archive

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