Fig. 2: Inferred ancestral polar and nonpolar niches for viruses.

a Ancestral “Polar” and “Nonpolar” states were estimated using the phylogenetic tree based on a one-parameter equal rates model. The outermost layer shows the taxonomy of six main groups. The boxplots in the second layer show the temperature optima of the viral genomes. For each box, n = 10,000 temperature values were analyzed as outlined in the methodology section on robust ecological optimum and tolerance. Only polar and nonpolar genomes were included in the tree. b The treemap diagram shows the number of viruses assigned to Polar, Nonpolar or “Unknown” biomes. Colors indicate the main taxonomic groups. c Relative Evolutionary Divergence (RED) values for viral main groups (n = 6) and families. N stands for the phylum Nucleocytoviricota (n = 17) and M stands for Mirusviricota (n = 5). d Histograms of RED values for the nodes at which “polar” or “nonpolar” adaptation events were inferred. RED values of child nodes in adaptation events were shown. For box plots, center lines show the medians; box bounds stand for the 25th and 75th percentiles; whiskers extend 1.5 times the interquartile range from the 25th and 75th percentiles; outliers are represented by dots. Source data are provided as a Source Data file.