An east–west distribution of genetic diversity in Nordic populations of caraway (Carum carvi L.) and its consequences for conservation prioritisation

Abstract The current global crisis of biodiversity loss calls for urgent conservation actions for many species, not the least wild species related to crop plants. These crop wild relatives are considered harbouring genetic diversity of major importance for future crop plant improvement, e.g. adaptation to climate change. Hence, their conservation needs to be a priority. To ensure the long-term conservation and to maximize the utility value of these species, it is important that as much of their genetic diversity as possible is conserved. Thus, the distribution of intraspecific diversity must be taken into consideration when planning conservation efforts. Caraway, Carum carvi L., has been cultivated since medieval times and is today one of the most important spice crops worldwide. In order to identify populations that would be of particular interest for in situ and ex situ conservation and for use in plant breeding we evaluated the geographic distribution of intraspecific diversity in populations of Carum carvi in the Nordic region (Iceland, Denmark, Norway, Sweden and Finland). Using a genotyping by sequencing approach, we genotyped 198 individuals from 16 Nordic populations. The amount of intrapopulation genetic diversity was similar among populations (mean H e = 0.29), and the diversity was structured in an east–westerly manner, probably reflecting colonisation patterns associated with different glacial refugia. In addition, some populations likely have a history shaped by human interventions. The results have important conservation implications and based on the outcome of this study, populations of conservation priority are suggested.