Aim The summits of mountain ranges at mid‐latitude in the Northern Hemisphere share many ecological properties with the Arctic, including comparable climates and similar flora. We hypothesize that the orogeny during the Oligocene‐Miocene combined with global cooling led to the origin and early diversification of cold‐adapted plant lineages in these regions. Before the establishment of the Arctic cryosphere, adaptation and speciation in high elevation areas of these mountain ranges may have led to higher species richness compared to the Arctic. Subsequent colonization 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 5,464 plant species from 756 genera occupying cold climates. We fitted a generalized linear model to evaluate the association between cold‐adapted plant species richness and environmental, as well as geographic variables. Finally, 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 indicate that the cold climatic niche appeared 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 indicates that most clades originated in central Asia between 39–7 Ma. Main conclusions Our results support the hypothesis that the orogeny and 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 colonization of the Arctic. Our results follow Humboldt's vision of integrating biological and geological context in order to better understand the processes underlying the origin of arctic‐alpine plant assemblages.

Spatially explicit simulations of gene flow within complex landscapes could help forecast the responses of populations to global and anthropological changes. Simulating how past climate change shaped intraspecific genetic variation can provide a validation of models in anticipation of their use to predict future changes. We review simulation models that provide inferences on population genetic structure. Existing simulation models generally integrate complex demographic and genetic processes but are less focused on the landscape dynamics. In contrast to previous approaches integrating detailed demographic and genetic processes and only secondarily landscape dynamics, we present a model based on parsimonious biological mechanisms combining habitat suitability and cellular processes, applicable to complex landscapes. The simulation model takes as input (a) the species dispersal capacities as the main biological parameter, (b) the species habitat suitability, and (c) the landscape structure, modulating dispersal. Our model emphasizes the role of landscape features and their temporal dynamics in generating genetic differentiation among populations within species. We illustrate our model on caribou/reindeer populations sampled across the entire species distribution range in the Northern Hemisphere. We show that simulations over the past 21 kyr predict a population genetic structure that matches empirical data. This approach looking at the impact of historical landscape dynamics on intraspecific structure can be used to forecast population structure under climate change scenarios and evaluate how species range shifts might induce erosion of genetic variation within species.

Summary The documentation of biodiversity distribution through species range identification is crucial for macroecology, biogeography, conservation, and restoration. However, for plants, species range maps remain scarce and often inaccurate. We present a novel approach to map species ranges at a global scale, integrating polygon mapping and species distribution modelling (SDM). We develop a polygon mapping algorithm by considering distances and nestedness of occurrences. We further apply an SDM approach considering multiple modelling algorithms, complexity levels, and pseudo‐absence selections to map the species at a high spatial resolution and intersect it with the generated polygons. We use this approach to construct range maps for all 1957 species of Fagales and Pinales with data compilated from multiple sources. We construct high‐resolution global species richness maps of these important plant clades, and document diversity hotspots for both clades in southern and south‐western China, Central America, and Borneo. We validate the approach with two representative genera, Quercus and Pinus, using previously published coarser range maps, and find good agreement. By efficiently producing high‐resolution range maps, our mapping approach offers a new tool in the field of macroecology for studying global species distribution patterns and supporting ongoing conservation efforts.