Strong differentiation between source and ex situ populations of rare plant species revealed by next‐generation sequencing

Societal Impact Statement Biodiversity is being lost rapidly worldwide due to factors such as climate change and habitat loss. To help safeguard plant populations, conservation strategies include seed banks and conservation cultures. However, it remains unclear how cultivation affects genetic variation compared with wild populations. Here, we compared genetic diversity and differentiation of wild populations and their corresponding conservation cultures in a conservation nursery using next‐generation sequencing. We found considerable differentiation between wild and cultivated populations, highlighting that current conservation culture practices should be improved to ensure genetic biodiversity is maintained for restoration efforts. Summary Ex situ conservation is an important element of modern conservation strategies and contributes significantly to the preservation of species and genetic diversity. However, depending on the specific ex situ approach, genetic variation within and among populations may be affected, mainly due to bottlenecks or drift. In this study, the impact of ex situ cultivation on genetic variation was studied. Therefore, source populations of four strongly endangered plant populations ( Adenophora liliifolia , Dianthus sylvaticus , Teucrium scordium and Trollius europaeus ) were compared with their respective ex situ populations, which were cultivated in a conservation nursery, using next‐generation sequencing (MIG‐seq). Here, no significant effect of cultivation on genetic diversity and inbreeding was observed, but comparatively high levels of genetic differentiation were found among source and ex situ populations, even though the ex situ populations had only been cultivated for one generation. This might be attributed to either unrepresentative seed collection at the source sites, unconscious selection during plant production or genetic drift in the source populations since the time of seed collection. As populations are best adapted to local conditions and show the highest fitness under these conditions, minimising genetic differentiation between source and ex situ populations is a key goal for successful reintroduction. Therefore, genetic monitoring and the results it provides are a powerful tool to improve ex situ conservation. Unfortunately, it is rarely applied in nature conservation at present.