Paternity analysis of Populus nigra L. offspring in a Belgian plantation of native and exotic poplars

Gene flow from cultivated poplar plantations into wild populations of Populus nigra L. is considered to represent a potential threat to the survival of P. nigra. In this study we investigated if pollen competition of Populus nigra L. and Populus × canadensis Moench in fertilising P. nigra ovules detected in a greenhouse experiment also occurs under field conditions. The results confirm non-random mating between males of P. × canadensis and P. nigra in fertilizing P. nigra females in the artificial species-mixed Belgian poplar stand. A paternity analysis also revealed non-random intra-specific mating patterns within P. nigra in the stand. No paternities were assigned to the male cultivar P. nigra cv. Italica. Practical implications for the conservation of wild P. nigra populations are discussed.