Europe-wide phylogeography and Approximatre Bayesian Computation challenge the native status of a conserved pond fish in Britain

Crucian carp are threatened by many environmental factors, including habitat loss and importantly competition and hybridisation with several non-native species in Europe. It is therefore essential that a comprehensive phylogeography of crucian carp be produced, in order to underpin conservation efforts. In this study, we used microsatellites and mitochondrial DNA to provide a phylogeographic overview of crucian carp in Europe. However, in doing so we uncovered similarities between British and continental European crucian populations. We therefore investigated this further with the use of Approximate Bayesian Statistics, testing the hypothesis that crucian were in fact introduced into Britain by humans, instead of naturally colonising >8000 years ago across the once present Doggerland Land Bridge. The resulting demographic models consistently supported an introduction of crucian carp into Britain around the 15^th century, in line with the first records of fish introductions into the Britain. This human-introduced origin of crucian in Britain may have important implications for its conservation in the part of its range.