Data from: Mountain building, climate cooling and the richness of cold-adapted plants in the northern hemisphere

Aim The summits of mountain ranges at mid-latitude in the Northern
Hemisphere and the Arctic share many ecological properties including
comparable climate and similar floras. We hypothesise that the orogeny
during the Oligocene-Miocene combined with global cooling allowed the
origin and early diversification of cold-adapted plant lineages in these
regions. Before establishment of the Arctic cryosphere, adaptation and
speciation in high elevation areas of these mountains ranges may have led
to higher species richness when compared to the Arctic. Subsequent
colonisation from mid-latitude mountain ranges to the Arctic may explain
similar but poorer flora. Location Arctic-Alpine regions of the Northern
Hemisphere. Methods We mapped the cold climate in the Northern Hemisphere
for most of the Cenozoic (60 Ma until present) based on paleoclimate
proxies coupled with paleoelevations. We generated species distribution
maps from occurrences and regional atlases for 5464 cold-adapted plant
species from 756 genera occupying cold climates. We fitted a generalised
linear model to evaluate the association between cold-adapted plant
species richness and environmental as well as geographic variables. We
performed a meta-analysis of studies, which inferred and dated the
ancestral geographic origin of cold-adapted lineages using phylogenies.
Results We found that the subalpine-alpine areas of the mid-latitude
mountain ranges comprise higher cold-adapted plant species richness than
the Palearctic and Nearctic polar regions. The topo-climatic
reconstructions indicated that the cold climatic niche occurred first in
mid-latitude mountain ranges (42-38 Ma), specifically in the Himalayan
region, and only later in the Arctic (22-18 Ma). The meta-analysis of the
dating of the origin of cold-adapted lineages indicated that most clades
originated in central Asia between 39 and 7 Ma. Main conclusions Our
results support the hypothesis that the orogeny and the progressive
cooling in the Oligocene-Miocene generated cold climates in mid-latitude
mountain ranges, before the appearance of cold climates in most of the
Arctic. Early, cold mountainous regions likely allowed for the evolution
and diversification of cold-adapted plant lineages followed by the
subsequent colonisation of the Arctic. Our results are in line with
Humboldt’s vision of integrating biological and geological context in
order to better understand the processes underlying the origin of
arctic-alpine plant assemblages.