Crucian NorfolkDan Jeffries and Dr Bernd Hänfling

Genomic approaches (RADtag sequencing) are being used to examine the genetic impacts of introduced species; including genetic bottlenecks, hybridisation and introgression. Population genomic approaches are applied to the study of the crucian carp, Carassius carassius


The crucian carp, Carassius carassius is threatened in Europe by many environmental factors, perhaps the most important of which is introduced species. In island habitats such as ponds species introductions often result in population crashes in native species, which in turn result in genetic bottlenecks. Bottlenecks are a significant threat to individual populations and entire species; not only do they reduce diversity on which natural selection can act, they also increase genetic drift, thus decreasing the efficiency with which selection can act on the diversity that is left.

However, genetic bottlenecks are not the only threat that non-native species pose in this system; the non-native species; goldfish (Carassius auratus auratus), common carp (Cyprinus carpio) and gibel/prussian carp (Carassius auratus gibelio) also hybridise with the crucian carp, which brings a whole suit of problems. For example, introgression; the movement of alleles from one species into individuals of another, can result from the backcrossing of a hybrid individual with an individual of a parental species. This process works both ways, and in some cases can be adaptive, thus potentially increasing the fitness of an alien species in its introduced range. Introgression can also have detrimental impacts on the native species, disrupting gene complexes that have evolved over millions of years.

Not only are the above processes important facets of non-native species impacts, but they pose broad evolutionary questions which are addressed in this project. How robust is selection in the face of a genetic bottleneck? How common is introgression between native and non-native species? Can adaptive introgression facilitate species invasions?

Here we use Restriction site Associated DNA (RAD) sequencing, a recently developed technique which uses Next Generation Sequencing (NGS) technology to isolate tens of thousands of molecular markers (SNPs) in non-model organisms. This approach provides the necessary power to look for introgressed regions and also to identify regions under selection.