Recruitment of a genotyped Quercus robur L. seedling cohort in an expanding oak forest stand: diversity, dispersal, and performance across habitats

Key message : Few studies have linked the origin of dispersed tree seeds with their post-dispersal fate. We show that habitat-dependent mortality in a pedunculate oak (Quercus roburL.) seedling cohort reshapes the effective fecundity of individual mother trees but has little effect on the cohort's genetic diversity. Context : Initial tree recruitment plays a key role in forest regeneration, yet little is known on how patterns of recruit mortality feed back on the fecundity of reproducing trees. Aims : To investigate how among-habitat variation in seedling arrival and survival alters initial patterns of genetic diversity and maternal reproductive success. Methods : We genotyped a pedunculate oak seedling cohort (n = 809) and monitored it over 3 years. The mother trees of 81% of the seedlings were identified through parentage analysis. Seedlings were assigned to one of three habitats (broadleaved forest, pine plantation, or open area). Results : Broadleaved forest received most seedlings (approximate to 65%) but their survival was reduced by a third compared with pine plantations or open areas. Thus, mother trees dispersing many descendants to broadleaved forest suffered a disproportionate reduction of their reproductive success. Genetic diversity did not vary among habitats, nor over the monitoring period. Conclusion : The quality of seed dispersal, in terms of delivery sites, can considerably influence the reproductive success of individual mother trees without affecting the overall genetic diversity of the recruits.PATRONS SPATIO-TEMPORELS DE COLONISATION DANS UNE POPULATION D'ARBRES EN EXPANSION: une approche integrant génétique et génomiqu