Genetic tools can significantly contribute to optimize plant translocation success, (1) by identifying target populations to restore and selecting the adequate source populations for translocation, and (2) by evaluating the effectiveness of plant translocations to restore or (re)create demographically viable and genetically resilient populations. Genetic methods, especially when they combine neutral and adaptive makers, allow inferring many key factors in translocation success (or failure), which cannot be assessed by a demographic approach: mating processes, contemporary gene flow, clonal extent, genetic quality of seed sources (sibship, parentage), inbreeding and outbreeding depression, contribution of sexual reproduction to recruitment, and admixture level (crosses between sources) in post-translocation established generations. A genetic approach can be particularly important when the remaining potential sources only consist of small census-sized populations or when there may be suspicion of clonal extent, small effective population size (Ne) or disrupted pollination.
We exemplify the different analyses combining molecular markers and fitness-related quantitative traits which are relevant for genetic assessment in designing plant translocations and for genetic monitoring of translocated populations, for the self-incompatible Arnica montana (Asteraceae) and Campanula glomerata (Campanulaceae) and the self-compatible Dianthus deltoides (Caryophyllaceae) in southern Belgium. The strategy to use several seed sources in a mixed planting design and to translocate a high number of founders in beforehand ecologically managed areas was successful in founding highly genetically diverse populations and in facilitating contemporary pollen flow, leading to admixed recruits (resulting from crosses between transplants from different seed sources) in the newly established generation, and to higher plant fitness due to heterosis in outcrossed progeny in Dianthus. However, source and translocated populations of the clonal Dianthus showed small contemporary Ne due to substantial selfing levels despite high flowering population sizes, emphasizing the importance of assessing the genetic quality of the transplants.