Fig. 2. New time-calibrated phylogeny and paleoclimate analysis.

a Time-calibrated phylogeny of 41 percomorph fish species, including 31 species of notothenioids and 10 outgroup fish species, generated with BEAST2³⁹. Branch length corresponds to time in million years (MYA) and grey rectangles show 95% highest posterior density intervals for node age estimates. All nodes received full support (Bayesian posterior probability = 1) except where noted. Species in bold were sequenced in this study. Branches for the Antarctic clade are highlighted in blue (cryonotothenioids), and non-Antarctic notothenioid species are marked in green. b Diversification of notothenioid species and temperature variation through time. Tree based on notothenioid species from panel a. The scatterplot shows data based on deep-sea δ¹⁸O benthic records which inversely reflect temperature with higher δ¹⁸O benthic corresponding to lower temperatures (green) and lower δ¹⁸O corresponding to higher temperatures (orange). The oxygen benthic is expressed as a ratio of two concentrations of oxygen isotopes³⁶; blue line shows moving average (Generalised Additive Model). Source data can be found in the Dryad repository at 10.5061/dryad.80gb5mktn.