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

Abstract

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 robur L.) seedling cohort reshapes the effective fecundity of individual mother trees but has little effect on the cohort’s genetic diversity. 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. To investigate how among-habitat variation in seedling arrival and survival alters initial patterns of genetic diversity and maternal reproductive success. 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). Broadleaved forest received most seedlings (≈ 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. 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.