The genus Populus diverged from the related Salix in the late Cretaceous (68.67 million years ago) in East Asia. The oldest find in the region of macroscopic remains of Populus kamaevae (section Takamahaca) from the Amur region dates back to the Late Danish – about 63 million years ago. It was in East Asia that the sections Leucoides, Tacamahaca and Aigeiros were separated in the early Paleocene. The initial settlement of North America occurred in the Paleocene (66–56 million years ago). It was the time of settlement of an ancient species or group that gave rise to the Abaso section on the mainland. In general, the development of poplar in North America occurred in several waves through intercontinental bridges. Sections Turanga, Populus (subsection Albidae) separated from other representatives no later than the early Paleocene and are relicts of the Madrean-Tethys floristic region. Representatives of the aspen subsection (Trepidae) appeared in the late Paleocene. Most modern species of the genus arose in the Middle and late Miocene, Pliocene and their age ranges from 15 to 3.5 million years. Hybridization, introgression and plastid capture are common facts in the evolution of the genus Populus. Studies of the historical development of species of the genus confirm the existence of a fairly wide gene flow between geographically close species, even belonging to different sections, but not reproductively isolated. Its presence should always be taken into account and not used as a factor of relationship in phylogenetic reconstructions.

Keywords: evolution of Populus, origin of the genus Populus, paleobotany, phylogeny, Populus, systematics of Populus