Cover Image:

Firs (Abies spp.) are keystone components of the boreal and temperate dark-coniferous forests and this genus harbors a number of relict taxa. Wei et al. (pages 2664-2682) reconstructed a transcriptomebased phylogeny and revealed the spatiotemporal evolution of global firs based on complete species sampling. Evolutionary and ecological analyses indicate that all extant firs underwent diversification in the Late Cenozoic, with the species richness distribution driven primarily by elevation and precipitation of the coldest quarter. Some morphological traits linked to elevational variation and cold tolerance may have contributed to the diversification of global firs. This work may inform forest management and species conservation in a warming world. The cover shows the dark blue cones of an alpine fir (Abies georgei var. smithii).