The introduction of species beyond their native range provides us with the opportunity to investigate the ecological and evolutionary processes that allow taxa to colonise and thrive in novel environmental conditions. Here I will present some recent and ongoing work on introduced populations of monkeyflowers (Mimulus spp.), native to the Americas, which colonised the British Isles 200 years ago. First, I will illustrate how we used next generation sequencing to compare the genomic structure of native and introduced populations of M. guttatus. Second, I will discuss how the introduction of monkeyflowers from opposite sides of the world into Britain in the 1800’s triggered hybridisation in closely related, but previously isolated, taxa. Genome duplication in these novel hybrids spawned one of the most recent examples of allopolyploid speciation: M. peregrinus. Using targeted genome sequencing at high read depth (>50x), we demonstrate the hybrid origin of M. peregrinus, and show that geographically separated populations in Scotland have been derived independently from local, sterile, plants.