Temperature variability and other climatic attributes linked to genomic features in the lichen-forming fungal genus Umbilicaria.

Background: Many species of lichen-forming fungi exhibit large geographical ranges and broad thermal niches, making them excellent models for investigating the genomics of climate adaptation. In this study, we examined the impacts of climatic variables on genomic features in 11 Umbilicaria species. We compared PacBio genomes of individuals from the same species collected in different climate zones: alpine, cold temperate, or Mediterranean.

Results: Our findings revealed several links between climatic and genomic features: (1) Selection pressure: in each climate zone, specific genes are under strong selection. (2) Genomic feature correlations: certain temperature variables (BIO2: mean diurnal range, BIO4: seasonality, BIO6: minimum in coldest month, BIO7: annual range) are correlated with GC content and the usage of the amino acids arginine and valine, suggesting these variables may drive convergent evolution of these genomic features. (3) Temperature variability: bioclimatic variables representing temperature variability, e.g. BIO2,4,7 are more influential in shaping genomic features than temperature means or extrema, with BIO6 also playing a significant role. (4) Epigenetic modifications: the rate of 5-methylcytosine (5mc) methylation within species is generally higher in samples from the colder habitat, suggesting that epigenetic modifications may contribute to climate adaptation.

Conclusions: Overall, our study shows that genome evolution is partially shaped by climate and, particularly, temperature variability. This aligns with numerous ecological and climate modelling studies, which show that climate variability has a stronger impact on species behaviour and evolution than climate means and extrema. Further genomics studies are required to provide additional evidence on this topic.