Effective gene dispersal and female reproductive success in Mediterranean maritime pine (Pinus pinaster Aiton)

Understanding population-scale processes that affect allele frequency changes across generations is a long-standing interest in genetic, ecological and evolutionary research. In particular, individual differences in female reproductive success and the spatial scale of gene flow considerably affect evolutionary change and patterns of local selection. In this study, a recently developed maximum-likelihood (ML) method based on established offspring, the Seedling Neighbourhood Model, was applied and exponentially shaped dispersal kernels were fitted to both genetic and ecological data in a widespread Mediterranean pine, Pinus pinaster Aiton. The distribution of female reproductive success in P. pinaster was very skewed (about 10% of trees mothered 50% of offspring) and significant positive female selection gradients for diameter (gamma = 0.7293) and cone crop (gamma = 0.4524) were found. The selective advantage of offspring mothered by bigger trees could be due to better-quality seeds. These seeds may show more resilience to severe summer droughts and microsite variation related to water and nutrient availability. Both approaches, ecological and of parentage, consistently showed a long-distance dispersal component in saplings that was not found in dispersal kernels based on seed shadows, highlighting the importance of Janzen-Connell effects and microenvironmental variation for survival at early stages of establishment in this Mediterranean key forest tree.