The importance of genetic diversity for the translocation of eight threatened plant species into the wild

Considering ongoing biodiversity losses, translocations of threatened plant species into the wild has become a common conservation technique although they are considered laborious, expensive and rarely successful. It is broadly accepted that the choice of suitable translocation sites and the translocation of many individuals increase their success. Moreover, high genetic diversity among introduced plants is suggested to be important but has been rarely assessed for populations of threatened species. Here, we tested whether higher genetic diversity generally increases early establishment of threatened plant species after a translocation. We translocated plantlets of eight rare and threatened species of Switzerland at one apparently suitable site per species. We planted 40 to 312 plants per site at two levels of genetic diversity, monoculture plots with offspring of single seed families per species, and mixture plots with offspring of several seed families per species. In the early translocation stages, plots with individuals of several seed families had a higher survival than plots with individuals of only one seed family, however, the positive effect of diversity disappeared with time. Our study suggests that a high genetic diversity is important at least for the short-term survival of translocated populations of threatened plant species. Translocations should therefore always aim to maximise genetic diversity in founder populations. Experimental approaches as the one we present here are important tools to realise long-term translocation experiments that are needed to enhance our understanding of the underlying factors responsible for success or failure of translocations of threatened plant species. We therefore recommend close collaborations between experimental plant ecologists, field botanists and conservation practitioners in future translocations of threatened species.