Fig. 2: The assembly dynamics of the Arctic flora and its potential driving factors.

a The rates of dispersal and in situ diversification of the Arctic lineages through time. MDisE maximal number of observed dispersal events per Ma. MDivE maximal number of observed in situ diversification events per Ma. b Schematic representation of the topography of parts of the Arctic and its adjacent regions in two phases, from the middle Miocene to the present (see Supplementary Table 3 for details). c Global temperature inferred from δ¹⁸O levels in benthic foraminifera¹⁸. d Sea-level fluctuations reconstructed from Pacific benthic foraminiferal δ¹⁸O and Mg/Ca records³⁶. e Changes in forest canopy openness inferred from C_est [(shrubs plus herbs)/trees] in northwestern Canada and Alaska³⁷. Green and blue dashed lines show a major deep-sea cooling and the first ‘deep’ glaciation, respectively⁴⁰. Source data are provided as a Source Data file.