Biology subjects

Magnusson, K. P.

Publications and source records attributed to Magnusson, K. P..

4 recordsLinked to original sources

bioRxiv2026

Genome-wide fluctuating selection under demographic cycling in Icelandic rock ptarmigan

Understanding how natural populations adapt to continuously shifting environments is central to evolutionary biology. Multi-annual population cycles impose temporally varying selective pressures, yet disentangling the resulting genomic signals from those of sustained directional selection and genetic drift has been challenging due to a lack of high-resolution temporal data. Here we investigate the genomic consequences of demographic cycling in a population of rock ptarmigan (Lagopus muta) from northeastern Iceland. We analyzed whole-genome sequences from 91 individuals sampled over an 11-year period, encompassing two population peaks (2010 and 2018) and two troughs (2007 and 2013). Testing allele frequency change at each SNP against a null model of drift and sampling, we identified candidate loci and grouped them by correlation of their temporal trajectories. Cluster trajectories fluctuated through time, and two were closely correlated with the regional census, one significantly tracking the demographic cycle, while a smaller set changed monotonically in a manner consistent with sustained directional selection. Each cluster contained loci distributed across many chromosomes, indicative of genome-wide responses to selection. The most strongly fluctuating loci overlapped candidate genes of possible functional relevance, most notably CTNNA2 (Catenin Alpha-2), which is associated with startle response and anxiety-like behaviors and may relate to predator avoidance. Our findings indicate that fluctuating selection comprises much of the temporal genomic response in this natural population, and suggest that multi-annual demographic cycles can drive rapid and widespread allele frequency change, highlighting the value of temporal genomics for clarifying the interplay between demography and natural selection in wild populations.

evolutionary biology↗

bioRxiv2023

A Chromosome-Level Genome Assembly for the Rock Ptarmigan (Lagopus muta)

The Rock Ptarmigan (Lagopus muta) is a cold-adapted, largely sedentary, game bird with a Holarctic distribution. The species represents an important example of an organism likely to be affected by ongoing climatic shifts across a disparate range. We provide here a high-quality reference genome and mitogenome for the Rock Ptarmigan assembled from PacBio HiFi and Hi-C sequencing of a female bird from Iceland. The total size of the genome is 1.03 Gb with a scaffold N50 of 71.23 Mb and a contig N50 of 17.91 Mb. The final scaffolds represent all 40 predicted chromosomes, and the mitochondria with a BUSCO score of 98.6%. Gene annotation resulted in 16,078 protein-coding genes out of a total 19,831 predicted (81.08% excluding pseudogenes). The genome included 21.07% repeat sequences, and the average length of genes, exons, and introns were, 33605, 394, and 4265 bp respectively. The availability of a new reference-quality genome will contribute to understanding the Rock Ptarmigans unique evolutionary history, vulnerability to climate change, and demographic trajectories around the globe and serve as a reference genome for the species in the family Tetraonidae (order Galliformes).

molecular biology↗

bioRxiv2023

Genomic vulnerability to climate change and mutation load are affected by past declines in effective population size in two sedentary arctic bird species

Using whole genome re-sequencing data we study the effects of climate influenced declines in effective population size on the accumulation of deleterious mutations and the response to future climate change in populations of cold-adapted avian sister species from the Holarctic: rock ptarmigan (Lagopus muta) and willow ptarmigan (Lagopus lagopus). We reconstruct the demographic histories of the populations and determine their nucleotide diversity, past and present inbreeding, and mutation load. Genomic vulnerability to future climate change scenarios (also known as offset) is predicted for the populations.. We show that relatively small and isolated populations have reduced nucleotide diversity, higher signatures of past and present inbreeding, and higher estimates of mutation load. Among the studied populations, the most vulnerable to a mismatch between current and predicted future environments are rock ptarmigan populations in East Greenland, Iceland, and Svalbard, while among willow ptarmigan, subspecies residing on the British Isles are the most vulnerable.

evolutionary biology↗

bioRxiv2018

Gas seepage pockmark microbiomes suggest the presence of sedimentary coal seams in the Oxarfjordur graben of NE-Iceland

Natural gas seepage pockmarks are found off and onshore in the Oxarfjorthur graben, NE Iceland. The bacterial communities of two onshore seepage sites were analysed by amplicon sequencing of 16S rDNA, along with determining the geochemical characteristics, hydrocarbon content and the carbon isotope composition of the sites.\n\nWhile one site was found to be characterised by biogenic origin of methane gas, with carbon isotope ratio {delta}13C [{per thousand}] = -63.2, high content of organic matter and complex hydrocarbons, the other site showed a mixed origin of the methane gas ({delta}13C [{per thousand}] = -26.6) with geothermal characteristics and lower organic matter content. While both sites harboured Proteobacteria as the most abundant bacterial phyla, the Deltaproteobacteria were more abundant at the geothermal site, and the Alphaproteobacteria at the biogenic site. The Dehalococcoidia class of the Chloroflexi phylum was abundant at the geothermal site while the Anaerolineae class was more abundant at the biogenic site. Bacterial strains from the seepage pockmarks were isolated on a variety of selective media targeting bacteria with bioremediation potential. A total of 106 strains were isolated and characterised, including representatives from the phyla Proteobacteria, Bacterioidetes, Firmicutes, and Actinobacteria. This article describes the first microbial study on gas seepage pockmarks in Iceland.

microbiology↗