Areas hosting hotspots of low-latitude marginal populations of coldadapted
plant species could be key areas for understanding geographical
attributes that result in refugia during climatic shifts as well
as the conservation of genetic diversity in the face of climate
change. Low-latitude populations of cold-adapted plants are important
because they may harbour the combination of alleles that foster
persistence in a warmer climate. Consequently, identification of
areas where arctic-alpine, circumpolar and circumboreal species
reach the low-latitude ends of their distribution will present a unique
opportunity to uncover processes that shaped current biogeographical
patterns, as well as prepare for future scenarios. Here, we identify
35 main marginal population hotspots (19 and 16 areas in North
America and Europe, respectively) of 183 plant taxa. These hotspots
represent areas where southern marginal populations of coldadapted
species co-occur. The identification of hotspots was based
on geographic overlap of southernmost locations of the target species,
in a 50 9 50 km grid. With a threshold of two species in a single
grid cell or in two contiguous cells, the analysis revealed that
hotspots are in most cases located in the southern portion of major
mountain chains. However, hotspots also occur in lowland areas at
high latitudes (Fennoscandia, Alaska, Hudson Bay) which do not
necessarily correspond to known cold- or warm-stage refugia (e.g.
Alps). Rockies and Sierra Nevada both in California and Spain, Apennines,
and the southern Scandes, maintain their hotspot status even
with more stringent cut-off thresholds (>3 and >5 species per cell
group). From a conservation point of view, our analysis reveals that
only a small portion of the hotspots are currently included within
protected areas. We discuss the importance of marginal population
hotspots to future research on climate change and, finally, outline
how conservation strategies can capitalize on the knowledge gained
from studying climate change effects on cold-adapted plants.
