The impact of ex situ cultivation on the genetic variation of endangered plant species – Implications for restoration

The ex situ cultivation of endangered plant species in botanic gardens reduces the loss of species and contributes to the preservation of genetic variation. However, ex situ cultivation may lead to changes of intraspecific variation, due to effects of bottlenecks, drift and interrupted gene flow. We applied molecular markers to compare genetic variation within and between ex situ and in situ populations of eighteen endangered plant species in order to analyse potential effects of ex situ cultivation on genetic variation. Genetic diversity varied strongly between species, but did not differ significantly between ex situ and in situ populations and was also not correlated with population size. However, genetic diversity of ex situ populations depended positively on the duration of cultivation. Furthermore, we observed a significant and mostly considerable genetic differentiation between ex situ and the respective in situ populations for all species, which tended to increase with the duration of ex situ cultivation. From our study, it can be concluded that ex situ cultivation does not necessarily result in a loss of genetic diversity and is therefore a well-suited approach to preserve intraspecific variation. However, our study also provided evidence for a potentially increasing genetic dissimilarity between ex situ and in situ populations during cultivation. Ongoing introduction of genetic material from in situ and a limited duration of ex situ cultivation are, therefore, essential prerequisites to avoid loss of genetic diversity as well as man-made differentiation under conditions of long-term ex situ cultivation.