Abstract
Human activities have increasingly introduced plant species far outside their native
ranges under environmental conditions that can strongly differ from those originally
met. Therefore, before spreading, and potentially causing ecological and economical
damage, non-native species may rapidly evolve. Evidence of genetically based adaptation
during the process of becoming invasive is very scant, however, which is due to
the lack of knowledge regarding the historical genetic makeup of the introduced populations
and the lack of genomic resources. Capitalizing on the availability of old nonnative
herbarium specimens, we examined frequency shifts in genic SNPs of the
Pyrenean Rocket (Sisymbrium austriacum subsp. chrysanthum), comparing the (i)
native, (ii) currently spreading non-native and (iii) historically introduced gene pool.
Results show strong divergence in flowering time genes during the establishment
phase, indicating that rapid genetic adaptation preceded the spread of this species and
possibly assisted in overcoming environmental constraints.