Data from: Phylogeographic pattern of range expansion provides evidence for cryptic species lineages in Silene nutans in Western Europe

As a result of recent or past evolutionary processes, a single species
might consist of distinct Evolutionary Significant Units (ESUs), even
corresponding to cryptic species. Determining the underlying mechanisms of
range shifts and the processes at work in the build-up of divergent ESUs
requires elucidating the factors that contribute to population genetic
divergence across a species’ range. We investigated the large-scale
patterns of genetic structure in the perennial herbaceous plant species
Silene nutans (Caryophyllaceae) in Western Europe. We sampled and
genotyped 111 populations using 13 nuclear microsatellite loci and 6
plastid single-nucleotide polymorphisms. Broad-scale spatial population
genetic structure was examined using Bayesian clustering, spatial
multivariate analyses and measures of hierarchical genetic
differentiation. The genotypic structure of S. nutans was typical of a
predominantly allogamous mating system. We also identified plastid
lineages with no intra-population polymorphism, mirroring two genetically
differentiated nuclear lineages. No evidence of admixture was found.
Spatial trends in genetic diversity further suggested independent
leading-edge expansion associated with founding events and subsequent
genetic erosion. Overall, our findings suggested speciation processes in
S. nutans and highlighted striking patterns of distinct stepwise
recolonisation of Western Europe shaped by Quaternary climate
oscillations. Two main potential ESUs can be defined in Western Europe,
corresponding to Eastern and Western nuclear-plastid lineages. In situ
preservation of populations and genetic rescue implying ex situ
conservation techniques should take the lineage identity into account.
This is particularly true in Great Britain, northern France and Belgium,
where S. nutans is rare and where distinct lineages co-occur in close
contact.