The historical connection of the Arctic and Qinghai-Tibet Plateau floras and their asynchronous diversification in response to Cenozoic climate cooling

The Arctic and the Qinghai-Tibet Plateau (QTP) are two northern regions
with the most extensive cold habitats on Earth and have undergone dramatic
warming in recent decades. However, we know little about the historical
connection of the Arctic and QTP biotas and their respective
diversification processes. Here, we used Meconopsis and Oreomecon, an
Arctic–QTP disjunct angiosperm genus pair with poor seed dispersal
abilities, to shed light on the evolutionary connection of the Arctic and
QTP floras and their respective diversification patterns. Our results show
that the Meconopsis-Oreomecon clade colonized the Arctic from the QTP in
the Late Eocene, suggesting the hitherto earliest known dispersal event
between the two regions. The Arctic Oreomecon split from the QTP
Meconopsis at ~34 Ma, associated with their climatic niche differentiation
and aridification of the Asian interior. Although both Oreomecon and
Meconopsis pre-adapted to open and low-temperature environments and had
similar diversification patterns, they diversified asynchronously in
respondence to different Cenozoic climate cooling events. The Arctic is
approaching its carrying capacity, whereas the QTP is still far from
saturation. These findings improve knowledge of evolutionary connection
and difference between Arctic and QTP floras, and have important
conservation implications given enhanced warming in both regions.