The success of rock translocation for populations of the chasmophytic Aeollanthus saxatilis (Lamiaceae)

To ensure the rescue, temporary conservation and further restoration of plant populations and communities threatened by exploitation, translocation appears to be an appropriate method in the context of mining. Little is known, however, on its effect on mutualistic interactions, such as pollination, and on the resulting plant population dynamics. Whole-rock translocations were performed as a conservation strategy for the endemic metallophyte flora of Katanga, Democratic Republic of the Congo. The aim of this study was to quantify the flower visitation, sexual reproduction and ramet demographic structure in such a translocated population, and to compare the data with those from natural populations of Aeollanthus saxatilis, one of the threatened species of the chasmophytic community. The study also documented the plant's flower visitor guild. The ramet density, demographic structure, pollination success and seed abortion rate were assessed in 10 quadrats per population, in the translocated population and in two subsisting natural populations. The flower visitation rate was quantified during three observation periods (20 min each) in six quadrats per population. Small differences were observed in the visitor guild between the translocated and natural populations, but the flower visitation rate was equivalent. No clear difference in the reproductive performance or ramet demographic structure of the populations was found. The flower visitor guild was mainly composed of generalist pollinators, which probably helped in establishing a functional visitor guild at the receptor site. Rock translocation therefore appears to be an encouraging approach, allowing the conservation of functional mutualistic interactions and the maintenance of a population structure comparable to that of natural chasmophytic plant populations.