Format: ORAL

La Auclair1 Olivier Brisset1, Jos Utg2, Nathalie Machon1, Paul Verdu2

1 CESCO, MNHN, CRNS, Sorbonne-Université, Paris, France 2 Eco-anthropology, CNRS, MNHN, Université Paris Cité, Paris, France

After the drastic decrease of population sizes of Arenaria grandifloras population in the Parisian region in the late 20st century, a translocation program was implemented in 1999. A preliminary study revealed that the main cause of the populations extinction was the low genetic diversity and the associated low fitness of the last individuals due to inbreeding depression. To save this species from extinction in this region, non-local and local plants were multiplied by in vitro culture and introduced in three sites of their natural area. The three translocated populations were funded with the same mixture of 450 individuals, 2/3 being clones of local plants and 1/3 of clones from non-local ones. To evaluate the outcome of the program, annual monitoring of plants fitness was carried out over 24 years, coupled with genetic analyses based on 13 microsatellite markers. First results highlighted that the newly-created populations showed an increase in genetic diversity compared to the founders, and displayed lower consanguinity due to higher heterozygosity level. These levels of diversity appear to be fairly stable from year to year, which was encouraging for the programs success. Interestingly, fluctuation in fitness were observed between individuals depending on the proportion of genome inherited from each founder population. To study this model in greater detail and gain a better understanding of the complex genetic processes that condition the success of programs based on assisted gene flow, we are currently resequencing the entire genomes of individuals sampled between 1999 and the present day By comparing simulations to actual genotypic data obtained from whole genome sequencing, it will be possible to assess whether natural selection phenomena linked to crossbreeding, such as heterosis or hybrid depression, have influenced the patterns of genetic diversity and how introduction of genotypes drove the genetic evolution of the population.