Biology subjects

Krokene, P.

Publications and source records attributed to Krokene, P..

6 recordsLinked to original sources

bioRxiv2025

A high-resolution, country-wide scenario analysis of forest susceptibility to spruce bark beetle damage in Norway

The European spruce bark beetle (Ips typographus (L.)) poses a growing threat to Norways forests under climate change, particularly in extensive spruce-dominated forests. Because controlling active outbreaks is notoriously difficult, reducing forest susceptibility through proactive management is essential. In this study, we used high-resolution simulations covering all of Norways forested land ([~]120,000 km2) to explore how different harvesting strategies affect long-term forest susceptibility to SBB damage. We compared a no-harvest baseline, a business-as-usual regime guided by economic criteria, and a risk-informed strategy that prioritizes harvesting of the most susceptible stands. Across two climate trajectories, we found that susceptibility-guided harvesting significantly reduced average forest susceptibility and fragmented high-risk areas, particularly in southern Norway. However, our results also reveal limitations to this approach: even with aggressive susceptibility-guided harvesting, long-term risk reductions plateau due to the homogenizing effects of even-aged forestry. Spatial connectivity analysis using electrical circuit theory further showed that susceptibility-guided harvesting disrupted landscape continuity among high-risk patches, suggesting a potential to constrain outbreak spread. These findings highlight the value of integrating susceptibility indicators and spatial connectivity metrics into forest planning to support adaptive, risk-informed management under climate uncertainty.

ecology↗

bioRxiv2023

Complex genomic landscape of inversion polymorphism in Europe's most destructive forest pest

In many species, polymorphic inversions underlie complex phenotypic polymorphisms and facilitate local adaptation in the face of gene flow. Multiple polymorphic inversions can co-occur in a genome, but the prevalence, evolutionary significance, and limits to complexity of genomic inversion landscapes remain poorly understood. Here, we examine genome-wide variation in one of Europes most destructive forest pests, the spruce bark beetle Ips typographus, scan for polymorphic inversions, and test whether inversions are involved in key adaptations in this species. We analyzed 240 individuals from 18 populations across the species European range and, using a whole-genome resequencing approach, identified 27 polymorphic inversions covering approximately 28% of the genome. The inversions vary in size and in levels of intra-inversion recombination, are highly polymorphic across the species range, and often overlap, forming a complex genomic architecture. We test several mechanisms, including directional selection, overdominance and associative overdominance that can contribute to the maintenance of inversion polymorphisms in the genome. We show that the heterogeneous inversion landscape is likely maintained by the combined action of several evolutionary forces and that inversions are enriched in odorant receptor genes encoding key elements of recognition pathways for host plants, mates, and symbiotic fungi. Our results indicate that the genome of this major forest pest of growing social, political, and economic importance harbors one of the most complex inversion landscapes described to date posing a question about limits of genomic architecture complexity.

evolutionary biology↗

bioRxiv2023

Drivers of asymmetrical insect invasions between three world regions

The geographical exchange of non-native insects can be highly asymmetrical, with some world regions exporting or importing more species than others. Several hypotheses have been proposed to explain such asymmetries, including differences in propagule pressure, environmental features in recipient regions, or biological traits of invaders. We tested aspects of these hypotheses in the context of the exchange of non-native insects between North America, Europe, and Australasia. Europe was the dominant exporter of non-native insect species between the three regions, with most of this asymmetry arising prior to 1950. The European dominance could not be explained by differences in import value, source species pool sizes, or native plant richness in the recipient regions. We identified that the introduction of non-native plants, driven in part by European colonization, best explains the asymmetrical exchange of non-native insects between our focal regions.

ecology↗

bioRxiv2022

Temperature-induced methylome changes during asexual reproduction trigger transcriptomic and phenotypic changes in Fragaria vesca

Plants must quickly adapt to a changing environment in order to maintain their fitness. One rapid adaptation mechanism that promotes plasticity is epigenetic memory, which may provide long-lived organisms the precious time needed to adapt to climate change. In this study, we used the perennial plant Fragaria vesca as a model to determine how the methylome and transcriptome adapt to elevated temperatures (28 vs. 18 {degrees}C) over three asexual generations. Changes in flowering time, stolon number, and petiole length were induced in responses to temperature treatment in one or more ecotypes after three asexual generations in a manner indicative of an epigenetic memory. Induced methylome changes differed between four different ecotypes from Norway, Iceland, Italy, and Spain, but there were also some shared responses. Elevated temperature conditions induced significant phenotypic and methylation changes, particularly in the Norwegian ecotype. Most of the differentially methylated regions (DMRs) were in the CHG context, and most CHG and CHH DMRs were hypermethylated. Notably, the four ecotypes shared only eight CHG DMR peaks. Several differentially methylated genes (DMGs) also showed a change in gene expression. Ecotype-specific methylation and expression patterns were observed for genes related to gibberellin metabolism, flowering time, epigenetics. Furthermore, when repetitive elements (REs) were found near ({+/-}2 kb) or inside a gene, they showed a negative correlation with gene expression. In conclusion, phenotypic changes induced by elevated temperatures during asexual reproduction were accompanied by changes in DNA methylation patterns. Also, positional influences of REs impacted gene expression, indicating that DNA methylation may be involved in both general and ecotype-specific phenotypic plasticity in F. vesca.

genomics↗

bioRxiv2020

A highly contiguous genome assembly of a major forest pest, the Eurasian spruce bark beetle Ips typographus

The Eurasian spruce bark beetle (Ips typographus [L.]), is a major killer of spruce forests across the Palearctic. During epidemics, it can destroy over 100 million cubic meters of spruce trees in a single year. Here we report a 236 Mb, highly contiguous I. typographus genome assembly using PacBio long-read sequencing. The final phased assembly had a contig N50 of 6.65 Mb in 272 contigs and was predicted to contain 23,923 protein-coding genes. Comparative genomic analysis revealed expanded gene families associated with plant cell wall degradation, including pectinases, aspartyl proteases, and glycosyl hydrolases. In todays forests, increasingly stressed by global warming, this resource can assist in mitigating bark beetle outbreaks by developing novel pest control strategies. Further, this first whole-genome sequence from the genus Ips provides timely resources to address important questions about the evolutionary biology and ecology of Curculionidae, the true weevils, one of the largest animal families.

genomics↗

bioRxiv2019

Induced and primed defence responses of Fragaria vesca to Botrytis cinerea infection

1.Strawberry is a high-value crop that suffers huge losses from diseases such as grey mould caused by the necrotrophic fungal pathogen Botrytis cinerea. Pesticides are heavily used to protect the strawberry crop, which raises environmental and human health concerns and promotes the evolution of pesticide resistant strains. Upregulating or priming the plants defences may be a more environmentally sustainable way of increasing disease resistance. Using Fragaria vesca as a model for the commercially grown octaploid strawberry Fragaria x ananassa, we investigated the transcriptional reprogramming of strawberry upon B. cinerea infection and the effectiveness of four priming chemicals in protecting strawberry against grey mould. First, we found that the transcriptional reprogramming of strawberry upon B. cinerea infection overlapped substantially with the transcriptome responses induced by Phytophthora cactorum (Toljamo et al., 2016), including the genes involved in jasmonic acid (JA), salicylic acid (SA), ethylene (ET) and terpenoid pathways. Furthermore, we investigated the effectiveness of previously identified priming chemicals in protecting strawberry against B. cinerea. The level of upregulated or primed resistance depended on the priming chemical itself ({beta}-aminobutyric acid (BABA), methyl jasmonate (MeJ), (R)-{beta}-homoserine (RBH), prohexadione-calcium (ProCa)) and the application method used (foliar spray, soil drench, seed treatment). Overall, RBH effectively primed strawberry defences against B. cinerea, whereas BABA and ProCa were not effective and MeJ showed mixed effects. Our results not only identify ways to effectively upregulate or prime strawberry defences against B. cinerea, but also provide novel insights about strawberry defences that may be applied in future crop protection schemes.

plant biology↗