Warming climates provide many species the opportunity to colonise
newly-suitable regions at higher latitudes and elevations. Despite
becoming warmer, higher latitudes and elevations nevertheless offer
novel climatic challenges, such as greater thermal variability and
altered frequency of weather events, and these challenges exert
selection on expanding populations. However, high gene flow and genetic
drift during the expansion phase may limit the degree to which species
can adapt to novel climatic conditions at the range front. Here we
examine how landscape topographic complexity influences the opportunity
for local adaptation to novel conditions during a range shift. Using
RAD-seq data, we investigated whether elevation, latitude, climatic
niche differentiation, and gene flow across a complex landscape were
associated with signatures of adaptation during recent range expansion
of the damselfly Ischnura elegans in Northeast Scotland. Our data
revealed two distinct routes of colonisation, with admixture between
these routes resulting in increased heterozygosity and population
density. Expansion rates, assessed as directional rates of gene flow,
were greater between more climatically similar sites than between
climatically divergent sites. Significant genetic structure and allelic
turnover was found to emerge near the range front at sites characterised
by high elevation, low directional gene flow, and high spatial
differentiation in climate regimes. This predictive combination of
factors suggests that landscape complexity may be a prerequisite for
promoting differentiation of populations, and providing opportunities
for local adaptation, during rapid or contemporary range shifts